__________________________________________________________________________________________________________________________________________SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright ? 2011 SAE International
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE.
TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerService@https://www.doczj.com/doc/269889900.html,
SAE WEB ADDRESS: https://www.doczj.com/doc/269889900.html,
AMS2770 I ssued 1974-06
Heat Treatment of Wrought Aluminum Alloy Parts
RATIONALE
AMS2770J revises start of soaking time (3.2.5.1), tightens controls over hydrogen induced porosity (3.3.3), revises pH requirements for water/polymer solutions (3.4.9.1) introduces a new requirement for hardness and conductivity after heat treatment (3.9), revises records (4.2) and inspection requirements (4.3), adds notes to Tables 4 and 7, and revises heat treatment parameters (see various tables). 1. SCOPE
1.1 Purpose
This specification specifies the engineering requirements for heat treatment, by part fabricators (users) or their vendors or subcontractors, of parts (See 8.8.1). It also covers heat treatment by warehouses or distributors converting raw material from one temper to another temper (See 1.3 and 8.5). It covers the following aluminum alloys:
1100, 2004, 2014, 2017, 2024, 2098, 2117, 2124, 2219, 2224, 3003, 5052, 6013, 6061, 6063, 6066, 6951, 7049, 7050, 7075, 7149, 7178, 7249, 7475
1.1.1 This specification may be used for heat treatment of parts made from other alloys provided the temperature,
temperature uniformity tolerances, times, and quenchants are specified or approved by the cognizant engineering organization (See 8.8.9).
1.2 Castings and parts made from castings shall be heat treated in accordance with AMS2771.
1.3 Temper Conversion
When a warehouse, distributor or similar organization converts raw material to a different temper, it shall be heat treated
and tested to the requirements of this specification. The marking, testing and reporting requirements shall also be in accordance with AMS2772 and the raw material specification.
2. APPL I CABLE DOCUMENTS
The issue of the following documents in effect on the date of the purchase order forms a part of this specification to the extent specified herein. The supplier may work to a subsequent revision of a document unless a specific document issue is specified. When the referenced document has been cancelled and no superseding document has been specified, the last published issue of that document shall apply.
2.1 SAE Publications Available from SAE I nternational, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), https://www.doczj.com/doc/269889900.html, .
AMS2658
Hardness and Conductivity Inspection of Wrought Aluminum Alloy Parts AMS2750
Pyrometry AMS2771
Heat Treatment of Aluminum Alloy Castings AMS2772
Heat Treatment of Aluminum Alloy Raw Materials AMS3025
Polyalkylene Glycol Heat Treat Quenchant ARP1962 Training and Approval of Heat-Treating Personnel
2.2 ASTM Publications
Available from ASTM I nternational, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, https://www.doczj.com/doc/269889900.html, .
ASTM D 445 Kinematic Viscosity of Transparent and Opaque Liquids (and the Calculation of Dynamic Viscosity)
3. TECHN I CAL REQU I REMENTS
3.1 Equipment
3.1.1 Pyrometry
Shall conform to AMS2750.
3.1.1.1
Solution heat treating furnaces shall be a minimum of Class 2 (±10 °F or ±6 °C). 3.1.1.2
AMS2750 furnace classifications for aging shall be as follows: 3.1.1.2.1
Aging ovens operating at or below 300 °F (149 °C) shall be a minimum of Class 2 (±10 °F or ±6 °C). 3.1.1.2.2
For alloys 7049, 7149, 7249 and 7050, aging ovens or aging furnaces operating above 300 °F shall be a minimum of Class 1 (±5 °F or ±3 °C). 3.1.1.2.3
For aging all other alloys, all ovens or furnaces operating above 300 °F (149 °C) shall be a minimum of Class 2 (±10 °F or ±6 °C). 3.1.1.3 Annealing and stress relieving furnaces shall be a minimum of Class 5 (±25 °F or ±14 °C).
3.1.2 Furnaces
3.1.2.1 Heating Media
Shall be air, molten salt bath, oil bath, or fluidized bed. The products of combustion and other materials that could contaminate parts shall not come into contact with parts during solution heat treating, annealing or stress relieving. Electrical heating elements and radiant tubes shall be shielded to prevent parts from being exposed to direct radiation. Shield construction and placement shall be such as to prevent parts from being exposed to re-radiation of heat from electrical elements or radiant tubes. Composition and maintenance of salt baths and fluidized beds shall be such as to prevent attack of the parts.
--``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
3.1.2.2 Temperature Uniformity Test Recovery Requirements (See 8.8.11)
For all solution heat treat and aging furnaces, the lag time between recovery of the first test thermocouple and the last test thermocouple to within 10 °F (6 °C), or 5 °F (3 °C) as applicable, of the set temperature during furnace uniformity tests shall not exceed the following:
3.1.2.2.1 Furnaces Tested Without a Load
20 minutes.
3.1.2.2.2 Furnaces Tested With a Load
40 minutes.
3.1.2.3 Furnaces Used for Alclad Material
Heat input of furnaces used for solution heat treating of parts made from alclad product shall be sufficient to ensure conformance to 3.3.4.
3.1.3 Racks and Fixtures
Shall be constructed so as to preclude entrapment of water, molten salt and/or water/polymer solutions.
Equipment
3.1.4 Quenching
3.1.
4.1 Equipment shall be provided for quenching in water, and/or water/polymer solutions, and for measuring
quenchant temperature. Provisions shall be made for mechanical or hydraulic agitation of the quenching medium and/or agitation of the parts and for heating and cooling of the quenchant, as necessary to conform to
3.4.2 and 3.4.3. Air agitation shall not be used.
3.1.
4.2 Quench tanks shall be located in proximity to solution heat treating furnaces so that the quench delay
requirements of Table 5 can be met.
3.1.
4.3 The quenchant volume shall be sufficient to prevent the quench tank temperature from rising more than
permitted in 3.4.3 during quenching with a maximum load.
Equipment
3.1.5 Refrigeration
Refrigerators, dry ice boxes, or liquid baths shall be provided for cold storage of parts when retention of the as-quenched (AQ) temper is required. Refrigerators, dry ice boxes with fans and liquid baths shall be equipped with a temperature recorder. Refrigerators shall be capable of temperature recovery to within 5 °F (3 °C) of the set temperature within 20 minutes of door closing after insertion or removal of parts.
3.2 General Procedures
3.2.1 Parts requiring a heat treatment to produce a final “T” temper shall be solution heat treated (including quenching),
refrigerated when necessary, and aged when required, as specified herein (See 8.8.1). Heat treatment shall be performed only on entire parts, never on a portion or section of a part.
3.2.2 Cleaning
Prior to solution heat treating or annealing, parts shall be clean and visually free of contaminants such as dirt, metal residues, lubricants and solvent residues. Residue from heating and quenching media shall be removed from parts after any heat treatment step.
--``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
3.2.3
Racking and Spacing 3.2.3.1 Parts, except rivets and other small parts (See 3.2.3.2), shall be racked or supported to permit free access of
the heating and quenching media to all surfaces of parts in all portions of the load.
3.2.3.1.1 Solution Heat Treating
Parts, 0.250 inch (6.35 mm) and under in nominal thickness, shall be separated by not less than 1 inch (25 mm). Thicker parts shall be separated by at least 1 inch (25 mm) plus the part thickness. (Complex parts and parts of large plan form (See 8.8.12) may require greater separation.)
3.2.3.1.2 Aging, Annealing and Stress Relieving
Parts shall be separated by not less than 1 inch (25 mm) except thin parts may be nested providing thickness of nested stacks does not exceed 1 inch (25 mm) and stacks are at least 1 inch (25 mm) apart.
3.2.3.2 Rivets and Other Small Parts
May be heated and soaked in baskets or in continuous furnaces. Arrangement in baskets may be either orderly or random. Parts may touch but shall not be nested; free access of the quench media to most surfaces must be maintained. Maximum thickness of layers of rivets or parts in baskets or on a moving belt, and minimum space between layers, shall be 2 inches (51 mm).
3.2.4 Salt Entrapment
Parts that can entrap salt shall be racked so as to preclude salt entrapment as much as practicable.
3.2.5 Soaking 3.2.5.1 Start of Soaking Time
Soaking time starts when all temperature control, recording and monitoring sensors reach the minimum of the uniformity tolerance range specified in 3.1.1.1, 3.1.1.2, or 3.1.1.3, as applicable. Load sensors should not be used to determine start of soaking time (See 8.3).
3.2.5.2 Soaking Times
The minimum soaking time shall be based on furnace control sensor(s) and, for solution heat treating, shall conform to Table 3 based on the thickness (minimum dimension of the heaviest section) at the time of heat treatment (See 8.4). The minimum soaking times for the second step of 7475 solution heat treatment are 15 minutes for alclad and 60 minutes for bare product. For all alclad products, the maximum soaking time is 10 minutes longer than the minimum.
3.2.5.3 I
nterruptions
During solution heat treatment, soaking shall be performed without interruption. During aging, annealing, stress relieving, and heat treatment to the O1 (formerly T411) temper, a maximum of four interruptions, with doors open for not more than 2 minutes during each, is permissible for removal or loading of parts. Door opening durations greater than 2 minutes are permitted provided the time between the door opening and recovery of furnace temperature is not included in the total time.
3.3 Solution Heat Treating - Heating and Soaking
3.3.1 Temperature
Parts that require solution heat treatment shall be soaked at the temperature specified in Table 2.
3.3.2 Furnace Temperature Stabilization
3.3.2.1 For air furnace loads where the previous load was at a higher set temperature, or the prior temperature
uniformity test was in a loaded furnace, furnaces shall be stabilized at the new set temperature before loading parts.
3.3.2.2 If the prior temperature uniformity test was in an unloaded furnace, furnace loads of non-clad material may be
loaded in a cold furnace or furnace whose previous set temperature was below the new set temperature.
3.3.2.3 For parts made from alclad material, furnaces shall be stabilized at the set temperature before loading parts.
3.3.3 Prevention of Hydrogen Induced Porosity
Entrapped water shall be prevented from entering the furnace. The loading of parts directly from a water-containing quench tank (i.e., wet parts), into a furnace is prohibited. Ammonium fluoborate, or equivalent, should be used in air furnaces as necessary; however, purging the furnace with fresh air may be necessary to prevent discoloration of subsequent loads of parts made from alclad product.
3.3.4 Recovery Time for Alclad Parts
For solution heat treating of parts made from alclad product under 0.125 inch (3.18 mm) thick, the furnace recovery time shall not exceed 30 minutes and for parts made from heavier alclad product, shall not exceed 60 minutes.
3.3.5 Multiple Solution Heat Treatments of Alclad Product
Parts made from product over 0.125 inch (3.18 mm) in nominal thickness shall be limited to two solution heat treatments in addition to any by the material producer. Parts made from product 0.020 to 0.125 inch (0.51 to 3.18 mm) in nominal thickness, shall be limited to one additional solution heat treatment in addition to any by the raw material producer. For parts made from product under 0.020 inch (0.51 mm) in nominal thickness, additional solution heat treatments are prohibited.
3.4 Solution Heat Treating - Quenching
3.4.1 Following completion of the required soaking, parts shall be quenched by immersion in water or in a
water/polymer solution conforming to the requirements of Table 4, except where the use of alternate quenched media is allowed for 6xxx series alloy parts per 3.4.6. Parts are in the AQ (as-quenched) temper immediately after quenching (See 8.8.7).
Temperature
3.4.2 Quenchant
At the start of quench, quenchant temperature shall not exceed 90 °F (32 °C) except when water quenching parts made from forgings. When quenching parts made from forgings, the start of quench water temperature shall conform to Table 1.
TABLE 1 - QUENCHING TEMPERATURE FOR FORGINGS
Temperature
Alloy Quenching
2014 150 to 180 °F (66 to 82 °C)
2024, 2219, 6061, 7075 140 to 160 °F (60 to 71 °C)
7049, 7149, 7249, 7050 130 to 160 °F (54 to 71 °C)
--``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
3.4.3 Temperature Rise of Quenchant During Quenching The quenchant temperature shall not exceed the maximum start-of-quench temperature specified in 3.4.2 by more than 10 °F (6 °C) at any time during quenching. In addition, the quenchant temperature shall not increase more than 25 °F (14 °C) from the starting temperature as a result of quenching any single load.
3.4.4 Quench Delay Times
Shall conform to Table 5.
3.4.5 Agitation
Parts and/or quenchant shall be agitated during quenching. For thin, parts (minimum dimension in heaviest section is under 0.105 inch (2.67 mm), movement into the quenchant during immersion is sufficient agitation.
3.4.6 Quenchants Other Than Water or Water/Polymer Solutions for 6061, 6063, 6066 and 6951 Alloy Parts
Thin parts under 0.125 inch (3.18 mm) in nominal thickness, made from 6061, 6063, 6066 and 6951 alloys, may be quenched in an air blast, water spray or fog, providing that the quality assurance provisions specified herein are supplemented by tensile and hardness tests as specified in 4.4.1.2.2. 3.4.7 I
mmersion Time
Parts racked or in baskets shall be kept immersed in the quenchant for not less than 1 minute per inch (25.4 mm) of maximum thickness, or fraction thereof, or for not less than 1 minute after all evidence of boiling ceases, whichever is longer. Sheet metal parts less than 0.125 inch (3.18 mm) thick may be removed from the quenchant as soon as all boiling ceases.
3.4.8 When water quenching from a salt bath, if the water quench tank does not have an overflow system to preclude
salt build-up in the quench tank, parts shall be rinsed in fresh water to preclude the possibility of salt residue on parts.
3.4.9 Water/Polymer Solutions 3.4.9.1 Water/polymer solutions shall conform to AMS3025, Type 1 or Type 2. Concentrations shall comply with
Table 4. The pH of water/polymer solutions shall be maintained between 7.5 and 9.0.
3.4.9.2
After quenching into a water/polymer solution, parts shall be thoroughly rinsed with fresh water to remove the residual polymer. 3.4.9.3 Polymer Concentration Control
3.4.9.3.1 Test Methods
Determination of concentration shall be based on tests of viscosity (in accordance with ASTM D 445) or by refractive index using a refractometer, e.g., °Brix, glycol coolant, salinity, specific gravity, Abbe, etc., calibrated in accordance with
3.4.9.3.6. A refractometer scaled in °Brix is preferred.
3.4.9.3.2 Test Frequency
Concentration shall be determined quarterly by viscosity. In addition, concentration shall be determined weekly, and when concentration is changed, by viscosity or refractive index.
3.4.9.3.3 When refractometer concentration measurement is made, the concentration of the tank shall be recorded as
the value determined by the corrected refractive index measurement (See 3.4.9.3.6).
3.4.9.3.3.1 Quenchants Used With Salt Bath Furnaces
When a refractometer is used, and a test of the quenchant shows that its salt content has changed by 1% or more since the last viscosity test, a new multiplying factor shall be determined (See 3.4.9.3.6.3) . Determination of the new multiplying factor shall be based on a new viscosity test or calibration against solutions of similar concentration in accordance with 3.4.9.3.4.
3.4.9.3.4 When a viscosity concentration measurement is taken, the reading shall be compared to the corrected
refractive index concentration measurement (See 3.4.9.3.6) taken on the same sample. For the purpose of
comparison, the viscosity value and refractive index value shall be rounded to the nearest 0.5% polymer
concentration. If the concentration value of the two measurements differ by 2% or less, the concentration of
the tank shall be recorded as the value determined by the refractive index measurement. I f the rounded
corrected concentration values of the two measurements differ by more than 2%, the reasons for the variance
shall be determined and corrective action taken.
3.4.9.3.5 Equipment
3.4.9.3.5.1 Refractometers use for determination of concentration shall be temperature compensating, and of a range
suitable for the concentration being measured.
3.4.9.3.5.2 Refractometers, when checked against standards, shall have a measurement accuracy of ±0.5% polymer
or ±0.3° Brix as applicable, with a scale resolution or minimum indication of ±0.2° Brix (or equivalent).
3.4.9.3.6 Calibration of Refractometers
3.4.9.3.6.1 Refractometers shall be calibrated at 90-day intervals. The method of calibration shall be documented, and
a seal stating the date of calibration shall be affixed to the refractometer.
A
3.4.9.3.6.2 Method
Refractometers may be calibrated against prepared polymer solutions of known composition. The calibration solutions may be prepared either by a volumetric or a weight method. Calibration points shall bracket each concentration and shall be within 2% of the tank concentration to be measured. The tank concentration shall be determined by adjusting the refractometer reading according to a calibration factor, curve or table resulting from the calibration.
B
3.4.9.3.6.3 Method
Refractometers may be calibrated against known refractive index standards. These standards can be created using carefully weighed amounts of sucrose in water. Alternatively, NIST traceable refractive index standards can be purchased (such as °Brix or refractive index prisms). Three points (zero, midpoint and span of the refractometer) are required. Concentration of either AMS3025 Type 1 or Type 2 polyalkalene glycol (PAG) is determined by dividing the reading on the refractometer by the concentration of the same sample determined by viscosity. This multiplying factor is then applied to subsequent concentration determinations by refractometer. A new multiplication factor is determined at each concentration determination by viscosity in accordance with ASTM D 445.
3.4.9.3.6.4 The calibration curve for each specific fluid shall accompany each refractometer.
3.4.9.3.6.5 For quenchants used with salt bath furnaces, the calibrating solutions shall contain known amounts of salt,
and the calibration method shall incorporate the effects of the salt.
3.4.9.3.6.6 Alternative Calibration Methods
Calibration methods different from 3.4.9.3.6.2 or 3.4.9.3.6.3 may be utilized when approved by the cognizant engineering organization.
Contamination
3.4.9.4 Salt
Salt content in polymer/water quenchants shall not exceed 6.0% by weight. Water/polymer quenchants used with salt bath furnaces shall be tested for salt content weekly. The method used shall be calibrated against solutions containing known amounts of both polymer and salt, and the procedure documented. Meters used to determine the salt concentration shall be calibrated every 90 days. Quench tanks which exceed 6.0% salt content shall not be used until the salt content has been reduced below 6% or the quenchant has been replaced.
3.5 Refrigeration
3.5.1 Parts requiring retention of the as quenched (AQ) condition after solution heat treatment shall, after quenching, be
refrigerated in conformance with the requirements of Table 6.
3.5.2 Prechilling
Prior to refrigeration, parts may be prechilled by immersion in a cooled liquid to accelerate cooling.
3.6 Aging
3.6.1 Parts requiring aging shall be aged as specified in Table 7.
3.6.2 Straightening After Aging
Straightening of parts in the following tempers is prohibited unless approved by the cognizant engineering organization: T6, T6X, T7, T7X, T8 and T8X as well as parts in the T4 and T4X tempers which have aged sufficiently at room temperature to meet either the hardness or conductivity minimum of AMS2658.
3.7 Annealing and Stress Relieving
3.7.1 Parts requiring annealing shall be heated, soaked and cooled as specified in Table 8.
3.7.2 A full anneal shall be used unless the treatment specified is a partial anneal or stress relief.
3.7.3 Except for material in the solution heat treated or aged condition, if a stress relief or stress relief treatment is
specified, the partial anneal parameters of Table 8 shall be used. The partial anneal (stress relief) treatments in Table 8 shall not be used to relieve residual stress in parts in the solution heat treated or aged condition.
3.8 O1 (Formerly T411) Temper
Parts required to be in the O1 temper shall be heated to the solution heat treating temperature specified in Table 2, soaked for the time specified in Table 3, and air cooled to room temperature.
3.9 Hardness and Conductivity: Hardness and conductivity requirements are established in AMS2658. Sampling and
testing shall be in accordance with 4.3.
3.10 Logs
A record (written or electronic storage media), traceable to temperature recording information (chart(s) or electronic storage media) and to shop travelers or other documentation, shall be kept for each furnace and load. The information on the combination of documents shall include: equipment identification, approved personnel’s identification, date; part number or product identification, number of parts, alloy, lot identification, AMS2770 (or other applicable specification), actual thermal processing times and temperatures used. When applicable, atmosphere, quench delay, quenchant type, polymer concentration, and quenchant temperature shall also be recorded. The maximum thickness, when process parameters are based on thickness, shall be recorded and shall be taken as the minimum dimension of the heaviest section of the part. The log data shall be recorded in accordance with the heat treater’s documented procedures.
3.11 Temper Conversion
When a warehouse, distributor or similar organization converts raw material to a different temper, it shall be heat treated and tested in accordance with the requirements of this specification. The marking, testing and reporting shall be in accordance with AMS2772 and the material specification.
3.12 Qualification of Vendors (Subcontractors)
Facilities performing heat treatment in accordance with this specification shall be approved by the cognizant quality assurance organization.
3.13 Personnel Training
Companies performing heat treatment in accordance with this specification shall have a verifiable program (either company-created or conforming to ARP1962) of initial and periodic training and evaluation of its personnel. The training program shall consist of one or more of the following: on-the-job training, classroom instruction, academic instruction.
4. QUALITY ASSURANCE PROVISIONS
4.1 Responsibility for Inspection
Except as specified by the purchasing documents, the processor shall be responsible for the performance of all tests and inspections specified herein. The procuring activity reserves the right to perform any surveillance or tests or inspections of parts, and to review heat treating records and results of processor’s tests and inspections to verify that heat treating conformed to the specified requirements.
4.2 Records
Records shall be kept available for five years after heat treatment. The records shall contain all data necessary to verify traceability and conformance to the requirements of this specification.
4.3 Final Inspection
Inspection of heat treated parts shall be in accordance with 4.4.
4.4 Parts Control
4.4.1 Parts Other Than Rivets and Similar Small Standard Parts
Shall be tested in accordance with the following:
4.4.1.1 7xxx Alloy Parts in T7X Tempers
Every part shall be conductivity tested at the thickest section. Additionally, every part shall be hardness tested except, when approved by the cognizant engineering organization, hardness testing frequency may be reduced to not less than 25%. (Parts which exhibit low conductivity and/or high hardness may be given additional aging (See Table 7) and retested.)
4.4.1.2 6061, 6063, 6066 and 6951 Alloy Parts
Every part shall be hardness tested. 6061, 6063, 6066 and 6951 alloy parts should not be conductivity tested and shall not be rejected for failure to meet conductivity requirements of AMS2658.
4.4.1.2.1 6013 alloy parts shall be tested in accordance with 4.4.1.3.
4.4.1.2.2 Air Blast, Water Spray or Fog Quenched 6xxx Series Alloy Parts (See 3.4.6)
In addition to hardness testing in accordance with 4.4.1.2, tensile specimens shall be taken from each heat treat load. The specimens may be made from parts having the lowest hardness, or sample material representing the thickest section of the parts, located near the center of the load. Tensile properties shall conform to the applicable material specification.
4.4.1.3 Other Alloys or Other Tempers
Each lot (See 8.8.10) of parts in a “T” temper shall be hardness and conductivity tested. (Hardness and conductivity testing is not required for parts in the annealed or stress relieved condition.) Testing shall be in accordance with 4.4.1.3.1 or 4.4.1.3.2.
4.4.1.3.1 Every part shall be hardness tested and 10% of the parts shall be conductivity tested. The conductivity tested
parts should include those having the highest and lowest hardness.
4.4.1.3.2 Every part shall be conductivity tested and 10% of the parts shall be hardness tested. The hardness tested
parts should include those having the highest and lowest conductivity.
4.4.1.3.3 Tensile or Shear Testing
--``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
Alternatively, when tensile or shear testing is required, it may be substituted for the 10% hardness testing. Specimen(s) shall be made from a part selected at random, or a prolongation thereof, or from a sample of the product from which the parts were fabricated. The specimen(s) shall represent the maximum thickness of each lot of parts in each heat treat load. If any test result fails to meet to the applicable requirements, the entire lot shall be rejected and referred to the customer for disposition.
4.4.1.3.4 Sampling and Testing
In lieu of testing each part in accordance with 4.4.1.3.1 or 4.4.1.3.2, random samples of each lot may be tested for both hardness and conductivity when sampling is approved by the cognizant quality assurance organization. The sampling frequency shall not be less than 25 percent.
4.4.1.4 Testing and acceptance criteria for parts whose size or shape does not permit hardness or conductivity testing
shall be as follows:
4.4.1.4.1 Either the hardness or conductivity testing may be omitted provided every part is tested by the remaining
method. If this option is used, the report shall reflect that the parts could not be hardness (or conductivity)
tested due to size or shape, and that all parts were conductivity (or hardness) tested.
4.4.1.4.2 If parts can neither be hardness nor conductivity tested, testing and acceptance criteria shall be as specified
by the cognizant quality assurance organization.
4.4.2 Rivets and Similar Small Standard Parts If mechanical testing (e.g., tensile, shear) is not required on each lot, hardness testing is required on each lot of parts. In addition, conductivity testing is required on each lot of 7xxx alloy parts. Sampling shall be at the same frequency as required for the strength parameter by the part specification or drawing. For parts whose size or configuration precludes the above testing, representative (in alloy, thickness, and temper) coupons shall be tested based on furnace used as follows:
4.4.2.1 Parts Solution Heat Treated and Aged in Batch Type Furnaces
A minimum of three test coupons per lot shall have been randomly placed in each solution heat treatment and age load.
4.4.2.2 Parts Solution Heat Treated and/or Aged in Continuous Furnaces
A minimum of one test coupon per lot shall have been placed in each solution heat treating and aging furnace during each shift or 12 hours, whichever is less.
4.4.3 Failures
If any part or coupon fails to meet either hardness or conductivity requirements of AMS2658, every part (which can be tested) in the lot shall be tested. Parts, and parts represented by coupons, which fail to meet either requirement shall be rejected and referred to the customer for disposition.
4.5 Report/Certification
The heat treating processor shall furnish, with each shipment of parts, a certified quality assurance report, traceable to the heat treat control number(s), stating that the parts were processed in accordance with the requirements of AMS2770 (or other applicable specification). This report shall include: purchase order number, part number or product identification, alloy, temper/strength designation, quantity of parts in the shipment; identification of furnace(s) used; actual thermal processing times and temperatures used. When applicable, the report shall include: atmosphere type, quenchant (including polymer concentration range), hot straightening temperature and method of straightening (e.g., press, fixtures), actual test results (e.g., hardness, conductivity, tensile, shear, etc.), and a statement of their conformance/non-conformance to requirements. This data shall be reported in accordance with the heat treater’s documented procedures.
5. PREPARATION FOR DELIVERY
Not applicable.
6. ACKNOWLEDGMENT
Not applicable.
7. REJECT I
ONS
Not applicable.
8. NOTES
8.1 A change bar (l) located in the left margin is for the convenience of the user in locating areas where technical
revisions, not editorial changes, have been made to the previous issue of this document. An (R) symbol to the left of the document title indicates a complete revision of the document, including technical revisions. Change bars and (R) are not used in original publications, nor in documents that contain editorial changes only. --``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
8.2 Raw Material Heat Treatment
Production heat treatment by material producers and forge shops, or their vendors, of products listed below should be performed in accordance with the procurement specification and/or AMS2772 (See 8.8.8). Products applicable to AMS2772 are: Sheet, Plate, Foil, Bar, Rod, Wire, Extruded Shapes, and Forgings.
8.3 Use of Load Sensors
The mandatory soaking times for air furnace solution heat treatment (Table 3) and aging (Table 7) are based on using control sensors reflecting furnace air temperature. They include allowance for the lag between air temperature and metal temperature. Therefore basing the start of soaking on load sensors, and soaking for the Table 3 and 7 times, will result in excess soaking time. In the case of aging, this may result in reduced properties; in the case of solution heat treatment, it will increase clad diffusion. Use of load sensors should be limited to confirming that parts reached and, during soaking, remained within the allowable range, i.e., the range defined by applying the furnace temperature uniformity tolerance to the specified temperature.
8.4 Solution heat treatment soak times include allowances for the more uniform temperature distribution in salt
baths/fluidized beds than air furnaces and the extra lag time needed for part temperatures to reach the heating medium temperature in air furnaces.
8.5 Mill Furnished Tempers
The tempers listed below are normally furnished by producers and cannot be produced by users. Consequently, parts for which product in one of these tempers is specified should not be re-solution heat treated, annealed, or heat treated to the O1 (formerly T411) temper unless authorized by the cognizant engineering organization:
T3, T31, T36, T361, T37, T81, T86, T87, T351, T451, T651, T851, T861, T3510, T3511, T4510, T4511, T6510, T6511, T8510, T8511, T7651, T7351, T76510, T73510, T73511, T736510, T736511, T652, T654, T7352, T7354, T73651, T73652, T73654, T7451, T7452, T7454, T74510, T74511.
8.6 T736XX temper designations have been superseded by T74XX temper.
8.7 Aluminum Alloy Tempers are described in AS1990.
8.8 Terms used in AMS are clarified in ARP1917 and as follows:
8.8.1 Parts Heat Treatment
Heat treatment by a source other than the raw material producer. Product is tested to the requirements of the heat treat processing specification or to selected requirements of other specifications (See 8.8.8). Rivets are considered parts at any stage of manufacture.
8.8.2 Solution Heat Treatment
Heating an alloy at an elevated suitable temperature for sufficient time to allow soluble constituents to enter into solid solution where they are retained in a supersaturated state after quenching.
8.8.3 Aging (Precipitation Heat Treatment)
Soaking solution heat treated parts at a moderately elevated temperature or, for some alloys and tempers, at room temperature to enhance strength and corrosion resistance properties.
--``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
8.8.4 Annealing
A thermal treatment used to soften metal. A full anneal will soften product to develop maximum formability and ductility. A partial anneal (stress relief) is used when grain growth is a problem or when less formability or ductility than provided by a full anneal is acceptable.
8.8.5 Polymer
Quenchant
A water solution of polymer used to alter the quench rate, intended to minimize distortion and residual stresses.
8.8.6 O1 (formerly T411) Temper
A special annealed condition used to minimize warpage during machining. Response to ultrasonic inspection is better than with “F” or “O” temper product. This is not a final temper.
8.8.7 AQ Temper After Quenching
All alloys are in the AQ (as-quenched) temper immediately after quenching. After maximum delay time at room temperature or maximum refrigerated storage time (as listed in Table 6) has elapsed, they are in the W temper which is unstable, i.e., their properties are continually changing. After 96 hours, of room temperature aging, the 2xxx and 6xxx alloys achieve stable, or relatively stable, T4 or T42 tempers.
8.8.8 Raw Material (e.g., Sheet, Plate, Bar, Extrusions, Forgings, Castings)
Heat treatment is performed by or for the raw material producer and product is tested as required by the material specification (See 8.8.1).
8.8.9 Cognizant
A term applied to the engineering organization responsible for the design of the parts, its allied quality assurance organization, or a designee of those organizations.
8.8.10 Lot
A group of parts of the same part number and at the same stage of fabrication which have been either heat treated in the same load or, in the case of continuous furnaces, hand loaded salt baths, etc., have been heat treated continuously during a single shift, not to exceed a 12 hour period.
8.8.11 Recovery Time
The elapsed time between insertion of parts in a heating medium and start of soaking time.
8.8.12 Large Plan Form
A part which has a large planer surface area in relation to its thickness such as a plate or sheet.
8.9 Dimensions and properties in inch/pound units and the Fahrenheit temperatures are primary; dimensions and
properties in SI units and the Celsius temperatures are shown as approximate equivalents of the primary units and are presented only for information.
PREPARED BY AMS COMMITTEE “D” AND “AMEC”
--``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
TABLE 2 - SOLUTION HEAT TREATING TEMPERATURES Alloy Form Set Temperature
Notes °F °C
2004 Sheet 985 529
2014, 2017, 2117 All 935 502
2024, 2124, 2224 All 920 493
2098 All 970 521
2219 All 995 535
6013 Sheet 1000 538 10
Rod/Bar 985 529
6061 All 985 529 8
6063 All 985 529
6066 All 985 529
6951 All 985 529 12
7049, 7149, 7249 All 875 468 1, 2
7050 Forgings 880 471 2, 7, 11
7050 All Other 890 477 2, 7, 11
7075 Sheet under 0.05 inch (1.3 mm) when aged to T73, T76 temper
870 466 3, 6
7075 Sheet under 0.05 inch (1.3 mm) when aged to T6 temper
920 493 3
7075 Other 870 466 4, 9
7178 All 870 466
7475 Sheet, Plate under 0.500 inch (12.7 mm)
880 471 5
7475 Plate, 0.500 inch (12.7 mm) and over
890 477 5
NOTES:
1. The aging treatment for 7049, 7149 and 7249 alloys shall not be initiated until at least 48 hours at room temperature have
elapsed after quenching.
2. To avoid stress corrosion cracking of thick 7049, 7149, 7249 and 7050 parts, delay between quenching and start of aging
should not exceed 72 hours.
3. The 0.05 inch (1.3 mm) dimension refers to thickness at time of heat treatment.
4. If heat treater can positively identify the original raw stock as sheet or plate having a thickness of 0.05 to 1.0 inch (1.3 to
25 mm), inclusive, 920 °F (493 °C) may be used.
5. After normal soaking, increase temperature to 920 °F (493 °C) for alclad and 955 °F (513 °C) for non clad; minimum soaking
time at higher temperatures, 15 minutes and 60 minutes, respectively.
6. 870 °F is the preferred treatment to achieve adequate hardness and conductivity readings but 920 °F (493 °C) may be used to
improve tensile properties.
7. Solution heat treat temperatures as low as 870 °F (466 °C) may be used to control recrystallization and surface cracking
problems.
8. For 6061, an alternate solution heat treating temperature of 995 °F (535 °C) may be used.
9. Rivets, which are to be aged to the T73 temper may be solution heat treated at 875 °F (469 °C).
10. Should not be solution heat treated after forming because it has a tendency to develop a large grain structure due to
recrystallization.
11. Eutectic melting may occur at the specified temperature if the raw material was not properly homogenized or worked.
12. Applies to clad brazing sheet #21 and #22 - core is 6951 alloy.
--``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
TABLE 3 - SOLUTION HEAT TREATING SOAKING TIMES
Thickness (1) Inches Thickness (1)
Millimeters
Minimum soaking Time,
(hours:minutes) (2)(3)(4)
Salt and
Fluidized Bed Air Furnace
Up to 0.020, incl Up to 0.51, i ncl 0:10 0:20 Over 0.020 to 0.032, incl Over 0.51 to 0.81, i ncl 0:15 0:25 Over 0.032 to 0.063, incl Over 0.81 to 1.60, i ncl 0:20 0:30 Over 0.063 to 0.090, incl Over 1.60 to 2.29, i ncl 0:25 0:35 Over 0.090 to 0.125, incl Over 2.29 to 3.18, i ncl 0:30 0:40 Over 0.125 to 0.250, incl Over 3.18 to 6.35, i ncl 0:35 0:50 Over 0.250 to 0.500, incl Over 6.35 to 12.70, i ncl 0:45 0:60 Over 0.500 to 1.0, incl Over 12.70 to 25, incl 0:60 1:30 Over 1.0 to 1.5, incl Over 25 to 38, incl 1:30 2:00 Over 1.5 to 2.0, incl Over 38 to 51, incl 1:45 2:30 Over 2.0 to 2.5, incl Over 51 to 64, incl 2:00 3:00 Over 2.5 to 3.0, incl Over 64 to 76, incl 2:15 3:30 Over 3.0 to 3.5, incl Over 76 to 89, incl 2:30 4:00 Over 3.5 to 4.0, incl Over 89 to 102, incl 2:45 4:30
Over 4.0 Over 102 Add 0:15 per
0.500 inch
(12.7 mm) Add 0:30 per 0.500 inch (12.7 mm)
NOTES:
1. The thickness is the minimum dimension of the heaviest section at the time of heat treatment.
2. Soaking time starts when all thermocouples are within 10 °F (6 °C) degrees of the set temperature.
3. For alclad product, the maximum soaking time is 10 minutes longer than the minimum.
4. Minimum soaking times for second step of 7475 solution heat treatment are 15 minutes for alclad and 60 minutes for nonclad.
--``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
TABLE 4 - LIMITS FOR QUENCHING IN POLYMER SOLUTIONS
Polymer Type (1) Alloy Form
Maximum Thickness (3) Polymer (1)(4)(6)
Concentration %
Notes
I
nches Millimeters
12024 Sheet,
Extrusions
0.040
0.063
0.071
0.080
1.02
1.60
1.80
2.03
34 max
28 max
22 max
16 max
2
2
2
2 2219 Sheet, Extrusions 0.07
3 1.85 22 max 2 6061
Sheet, Plate, Bar
Extrusions
0.250
0.375
1.000
6.35
9.52
25.40
40 max
32 max
22 max
7049
7050
7075
Sheet, Plate
Bar
0.080
0.250
0.375
0.500
1.000
2.03
6.35
9.52
12.70
25.40
40 max
34 max
28 max
22 max
16 max
6061
7075
Forgings
1.000
2.000
2.500
25.40
50.80
76.20
18 to 22
11 to 15
8 to 12
5
5 7049
7149
Forgings
1.000
2.000
3.00
25.40
50.80
76.20
18 to 22
11 to 15
8 to 12
7050 Forgings
1.000
2.000
3.000
4.000
25.40
50.80
76.20
101.50
28 to 32
24 to 28
18 to 22
13 to 17
7049
7050
7075
Extrusions
0.250
0.375
6.35
9.52
28 max
22 max
22024 Sheet,
Extrusions
0.040
0.063
0.080
1.02
1.60
2.03
34 max
22 max
16 max
2
2
2 6061
7049
7050
7075
Sheet,
Plate,
Bar
0.040
0.190
0.250
1.02
4.83
6.35
34 max
20 max
18 max
6061
7075
Forgings
1.00
2.00
25.4
50.8
11 to 15
8 to 12 5
NOTES:
1. Type 1 and Type 2 polymer solutions and concentrations shall conform to AMS3025. Concentrations are percentages by volume of
the undiluted polymer as furnished by the producer.
2. Applicable when final temper is T4 or T42. When final temper is T6 or T62, sheet and plate up to 0.250 inch (6.35 mm), inclusive,
may be quenched in Type 1 or Type 2 polymer solution at 22% maximum.
3.Thickness is the minimum dimension of the largest section at the time of heat treatment.
4.Where only maximum concentration is shown, any 4% range may be used except the maximum shown shall not be exceeded. When
concentration is specified on a drawing or purchase order without tolerance or range the tolerance shall be ±2%.
5.Prohibited for 7075 alloy over 1 inch (25 mm) when final temper is T
6.
6. The minimum glycol percentage for any alloy, form or thickness grouping may be used for all listed thicknesses but may produce
variation in subsequent processing (e.g. machine distortion, aging time variations etc.).
--``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
TABLE 5 - MAXIMUM QUENCH DELAY TIMES (NOTE 1) Minimum Thickness (Note 2) Maximum Time Seconds
(Note 3) I
nch Millimeters
Up to 0.016, incl Up to 0.41, incl 5
Over 0.016 to 0.031, incl Over 0.41 to 0.79, incl 7
Over 0.031 to 0.090, incl Over 0.79 to 2.29, incl 10
Over 0.090 Over 2.29 15 NOTES:
1. The delay time is measured from the time the furnace door of an air furnace starts to open, or the first portion of the
load emerges from a fluidized bed or salt bath or the heating zone of a continuous furnace, to complete immersion of
the load in the quenchant.
2. Minimum thickness is the minimum dimension of the thinnest section of any part in the load.
3. The maximum quench delays specified may be exceeded providing tests made within the past year have
demonstrated that part temperatures do not fall below 775 °F (413 °C) before immersion except, for 2219 alloy, part
temperatures shall not fall below 900 °F (482 °C) before immersion.
TABLE 6 - REFRIGERATION
Alloy Maximum Delay Time
Between Quench and
Refrigeration Minutes Maximum Refrigerated Storage Time, Days, at Max Temp Shown 10 °F (-12 °C) 0 °F (-18 °C) -10 °F (-23 °C)
2XXX 15 1 30 90 Others 30 7 30 90
TABLE 7 - AGING TREATMENTS Alloy
Form Starting Temper
Final
Temper (2)Mand,Pref or Alt. (1)1st Step 2nd Step (14) (15) Notes (4)Temp Time (12)Temp Time (12)°F °C Hours °F °C Hours 2XXX Sheet AQ, W T4 M Room N/A 10 Other AQ, W T42 M Room N/A 10 2004 Sheet T4 T6 M 330 166 17 to 19 5
2014Sheet T3 T6 M 320 160 18 to 20 5
All T4 T42 T6 T62
M 350 177 8 to 9 52024 All AQ.W T42 M Room N/A 10
2024Sheet,
Plate,
Drawn Tube T3 T351 T81 T851 M 375 191 12 to 13 T361 T861 M 375 191 8 to 9 T42 T62 M 375 191 9 to 12 5
T42 T72 M 375 191 16 to 18 5
Forgings T4 T352 T62 T852
M 375 191 12 to 13 5Wire, Rolled Bar T351 T4 T851 T6
M 375 191 12 to 13 Extruded Bar and Shapes T351X T4 T42 T851X T6 T62 M 375 191 12 to 13 55
2098 All T351 T851 M 320 160 17 to 19 T42 T62 M 320 160 17 to 19 5
2124 Plate T351 T851 M 375 191 12 to 13
2219Alclad Sheet T42 T62 M 375 191 17 to 19 5
Forgings T42 T62 M 375 191 25 to 27 5
All Other T42 T62 M 375 191 35 to 37 5
Sheet T31 T81 M 350 177 17 to 19 T37 T87 M 325 163 23 to 25
Forgings T352 T852 M 350 177 17 to 19 T4 T6 M 375 191 25 to 27 5
Plate T351 T851 M 350 177 17 to 19 T37 T87 M 325 163 17 to 19
Rivets T31 T81 M 350 177 17 to 19
Extruded Bar and Shapes T31 T351X T81 T851X
M 375 191 17 to 19 --``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
TABLE 7 - AGING TREATMENTS (CONTINUED)
Alloy Form
Starting
Temper
(4)(5)
Final
Temper
(2)
Mand,
Pref or
Alt. (1)
1st Step 2nd Step (14)
Notes
(4)
Temp Time (12)Temp Time (12)
°F °C Hours °F °C Hours 6013 Sheet
AQ, W T4, T42 M Room N/A 10
T4, T42 T6, T62 M 375 191 4 to 5 5 6061
6063
6066
All
AQ, W T4, T42 M Room N/A 10
T4 T6 P 350 177 8 to 10 5
T42 T62 A 320 160 18 to 34 5 6951 Sheet (11)
AQ T4,
T42 M Room N/A 10 T4, T42 T6, T62 M 320 160 17 to 19 5 7049
7149
Extruded Bar and
Shapes
W T73 M 250 121 23-25 330 166 21-22 6,7,8
W T76 M 250 121 23-25 330 166 14-15 6,8 Forgings W T73 M 250 121 23-25 330 166 13-14 6,8
7050
Rivets AQ, W T73 M 250 121 4 Min 355 179 8 Min
Plate, Extruded
Bar, & Shapes
AQ,
W T73 M 250 121 6-8 350 177
11.5-12.56,8
Plate AQ,
W T76 M 250 121 6-8 350 177 6.5-7 6,8 All Except Plate AQ, W T76 M 250 121 6-8 350 177 3.5-4.5 6,8
All AQ,
W T74(9) M 250 121 6-8 350 177 6-8 6,8 7075
All AQ, W T6, T62 M 250 121 23-25
Sheet, Plate AQ, W
T73
P 225 107 6-7 325 163 26-28 3,8
A 250 121 4-5 350 177 8-10 3,8
T76
P 225 107 6-7 325 163 16-18 8
A 250 121 4-6 350 177 5-7 8
Wire, Rolled Bar,
Forgings
AQ, W
T73
P 225 107 6-7 350 177 8-10 8
A 250 121 4-5 350 177 8-10 8
T76
P 250 121 3-4 325 163 16-18 8
A 225 107 6-7 325 163 16-18 8
Extruded Bar &
Shapes
AQ, W
T73
P 225 107 6-7 350 177 6-8 8
A 250 121 4-5 350 177 6-8 8
T76
P 250 121 3-4 320 160 19-21 8
A 225 107 6-7 320 160 19-21 8
7178
All AQ,
W
T62
M
250
121
23-25
Sheet, Plate AQ, W T76
P 250 121 23-25 325 163 16-18 8
A 250 121 4-6 325 163 16-18 8
Extruded Bar &
Shapes
AQ, W T76
P 250 121 23-25 320 160 18-20 8
A 250 121 4-6 320 160 18-20 8
7249
Forgings W T73 M 250 121 10-12 325 162 6.5-7.5 6,8 Extrusions W T76 M 250 121 4-28 325 162 4-10 6,8
7475
Sheet
AQ,
W T61 M 250 121 3-5 315 157 3-3.25 8 AQ,
W T761 M 250 121 3-5 325 163 10-12 8 Plate
AQ, W T6 M 250 121 23-25
AQ,
W T76 M 250 121 3-5 325 163 12-18 8 AQ,
W T73 M 250 121 3-5 325 163 24-30 8 --``,,``,,,`,`,,`,,`,,``,,```,`-`-`,,`,,`,`,,`---
NOTES FOR TABLE 7 - AGING TREATMENTS:
1. (M) Mandatory, (P) Preferred or (A) Alternate Aging Treatment.
2. Digits added to these basic temper designations to denote stress relief treatments, etc. should appear identical before and after
aging.
3. Either second step age may be used with either first step age interchangeably.
4. For all T7XX tempers, the first step of the T7XX age may be omitted if parts (material) are (is) in the T6 temper.
5. When temper before furnace aging is AQ, W, T4, or T42, the furnace aging treatment may be started immediately after quenching
or at any time thereafter. With the exception of 7049, 7149 and 7249 alloys, natural aging is not necessary before initiating a -T6XX or the first step of -T7XX age.
6. The aging treatment for 7049, 7149 and 7249 parts shall not be initiated until at least 48 hours after quenching. To avoid stress
corrosion cracking of thick 7049, 7149, 7249 and 7050 parts, the elapsed time between quenching and start of aging should not exceed 72 hours.
7. 14 to 15 hours if thicker than 2 inches (51 mm).
8. Aging times at the specified second step temperature are permissible to reduce hardness and/or raise conductivity of T7XX parts in
order to meet AMS2658 requirements. Additional aging times allowed are as follows:
Additional aging (re-aging is permitted only for parts which exceed the specified minimum hardness for the alloy and temper by two points HRB or equivalent.
Additional aging (re-aging) shall be performed in cycles of 2 hours minimum plus 0.5 hour for each inch of thickness or fraction thereof in excess of 2 inches. Total re-aging time shall not exceed a total of 4 additional hours except that 6 additional hours for 7050 forgings thinner than 0.260 inches (6.60 mm) are allowed.
Additional aging (re-aging) cycles shall meet all applicable specification requirements and shall be documented as part of the
production records. Applicable hardness and conductivity tests shall be performed to verify compliance with the properties of 4.4.1 after each aging cycle.
Additional aging (re-aging) temperatures for specific alloys shall conform to the second step age requirements of Table 7.
U ninterrupted aging time may be used when additional aging time has been previously demonstrated. Total aging time shall not exceed aging time from Table 7 plus additional aging time in note 8.2.
Formerly designated T736.
T4 and T42 are achieved when hardness and conductivity per AMS2658 are met. Typically, this is achieved within 96 hours at room temperature.
Applies to clad brazing sheet #21 and #22 - core is 6951 alloy.
Soaking time shall conform to 3.2.5. All soaking times, except those for 7050 alloy and those referencing note 7, are for product or
nested stack up to 0.5 inch (12.7 mm) thickness (minimum dimension of heaviest section). Add 0.5 hours to times for each additional
0.5 inch (12.7 mm) or fraction thereof. Soaking times shown are applicable to all thicknesses of 7050 alloy. When using load
thermocouples to measure aging time, the soaking times for the 0.5 inch product shall apply.
Aging temperature and times for stress relieved tempers, TX5, TX51, TX51X and TX52 shall be the same as basic temperatures.
The second step aging process may be conducted in a continuous operation after the first step or the parts may be cooled to room temperature and then given the second step.