1、 WORLDWIDE ENGINEERING STANDARDS Material Specification GMW16579 Material and Process Testing Requirements for Press Hardened Steel and Stamping Suppliers Copyright 2012 General Motors Company All Rights Reserved May 2012 Originating Department: North American Engineering Standards Page 1 of 7 1 Sco
2、pe This document describes the minimum process and internal testing requirements for producers of hot stamped parts. 1.1 Material Description. Hot stamping, or press hardening as it is also known, utilizes a steel of high hardenability such as 22MnB5 that is heated to convert the microstructure to a
3、ustenite followed by stamping in a water cooled die to produce the proper part shape and to simultaneously quench the steel to create a martensite rich microstructure. Parts produced to this specification will have a uniform hardness and a microstructure consisting of essentially 100% tempered marte
4、nsite along with small amounts of bainite. 1.2 Symbols. Not applicable. 1.3 Typical Applications. Typical parts covered by this specification are those that require extremely high strength and are generally critical to passenger safety, side impact and provide passenger protection in the case of veh
5、icle roll over. These parts are found throughout the body structure and closures, with typical applications including door beams, B Pillar reinforcements, floor reinforcements and upper body roof rails. 2 References Note: Only the latest approved standards are applicable unless otherwise specified.
6、2.1 External Standards/Specifications. AIAG CQI-9 ASTM E140 ASTM E-8 2.2 GM Standards/Specifications. GMW3059 GMW14400 GMW3335 2.3 Additional References. Best Practice BODYSTR-33. The supplier shall work with the GM responsible engineer to comprehend this requirement. Statement of Requirements (SOR)
7、 Appendix N. TMC003 Material Safety Data Sheet guidance documents (available at ). 3 Requirements 3.1 Requirements on Test Specimens. Not applicable. 3.2 Marking. All parts shall be marked as shown in the SOR Appendix N and the Best Practice BODYSTR-33. 3.3 General Requirements. All sheet parts prod
8、uced to this specification shall be manufactured by approved suppliers to GM and will be shown as being approved to GMW14400. Approved suppliers are listed in the MATSPC system and can be provided by your GM Global Purchasing Supply Chain buyer. A change in steel suppliers is considered a significan
9、t process change and the stamping supplier will be required to update their Production Part Approval Process (PPAP) status before production begins. 3.3.1 GM must be notified prior to any steel supplier change. If a zinc based coating is specified (pure zinc or a zinc alloy) the source that produces
10、 the stamping is required to test and re-qualify to a PPAP Level 3. The stamping supplier will consult with Product Engineering and Materials Engineering when evaluating potential process and supplier changes. Copyright General Motors Company Provided by IHS under license with General Motors Company
11、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16579 Copyright 2012 General Motors Company All Rights Reserved May 2012 Page 2 of 7 3.3.2 Suppliers of hot stamped parts to GM are required to verify that incoming steels meet al
12、l specified material requirements. This shall include, but not be limited to: steel thickness, mechanical properties after heat treatment, coating weight and coating type (for coated products), bend test (parallel and transverse to rolling direction) and any other requirements determined by GM and/o
13、r the released part drawing/math data. The supplier is responsible to ensure that the steel, the heat treatment and stamping process, die cooling, post form trimming, etc., are capable of producing parts that meet all specified requirements. 3.4 Supplier Audits. Suppliers shall develop a Heat Treatm
14、ent Assessment Plan consistent with the requirements of Automotive Industry Action Group (AIAG) standard CQI-9. General Motors shall perform assessment audits to ensure suppliers are in conformance to these requirements. Completion of the CQI-9 audit is required before a hot stamper can be placed on
15、 the GM Approved Source List and supply parts to General Motors. Failure to be in compliance with the CQI-9 Audit standards shall result in removal from the opportunity to bid on future business and may result in the loss of current business. 3.5 Initial Part Verification Requirements. Suppliers sha
16、ll develop a verification plan for all parts they are awarded. This verification plan is to be developed before parts are used on any vehicle builds unless authorized by GM and the releasing engineer. This verification plan shall include control of initial production until the process is determined
17、to be in control by GM. Once the process is determined to be in control, a process control plan must be developed to ensure lot to lot consistency of all parts supplied to GM. Suppliers shall work with GM to determine the required testing frequency of each test, however, it is not required that each
18、 test be performed on every lot of material sent to GM. This testing shall include, at a minimum; mechanical properties, hardness (both Rockwell and Vickers microhardness as appropriate), part thickness profile, microstructure, coating thickness and thickness of coating alloys. 3.6 Supplier On-Site
19、Testing Requirements. Suppliers providing Press Hardened Steel (PHS) parts to General Motors are required to have on-site testing capability to perform part evaluations to ensure conformance to specification requirements and to monitor quality of parts as they are produced. The laboratory shall have
20、 operator(s) that have adequate training to perform such tests and operators shall be available to perform testing consistent with their quality plans during all shifts where parts are being produced. At a minimum, suppliers are required to be able to perform tests 3.6.1 thru 3.6.5. 3.6.1 Microstruc
21、tural Evaluation. Suppliers shall have the proper equipment to section, mount, polish, etch and microscopically examine samples with a metallurgical microscope to determine the phases present in test samples. 3.6.2 Hardness Testing. Suppliers shall have the capability to perform Rockwell and Vickers
22、 microhardness hardness testing. 3.6.3 Mechanical Properties. Suppliers shall have the capability to perform mechanical property testing with full size and sub size tensile bars following GMW3335 tensile testing requirements. 3.6.4 Photomicrographs. Photomicrographs of microstructures and microhardn
23、ess across sample parts. 3.6.5 Coating and Surface. Thickness testing, including part thickness, coating thickness and thickness of each alloy coating layer (coated parts), including the steel/coating interface layer. On uncoated steels, decarburization shall also be measured and reported. 3.7 Verif
24、ication Test Requirements. The supplier shall perform the following tests on production representative parts in order to validate their process. The sampling plan and number of parts to be tested will be established by Supplier Quality. The supplier shall keep samples from the bend test for examinat
25、ion by GM. 3.7.1 Part Thickness. The supplier shall cut at least 6 samples from a part selected from a production representative run and evaluate thickness in flat areas as well as in radii and any draw areas. No more than 20% thinning is allowed in any area of the part unless approved by engineerin
26、g. 3.7.2 Hardness. Suppliers shall have thermal imaging capability in each hot stamping facility to map the temperature of parts exiting the stamping die. Hardness shall be evaluated in the worst-case areas as indicated by hot spots on the thermal image of parts at die opening. Six hardness test loc
27、ations shall be established during PPAP and documented in the suppliers sample report and process control plans. Examples of areas to be evaluated shall include flat areas, the draw walls and bent areas. All locations shall meet the property requirements as shown in GMW14400, Appendix A, “Indirect a
28、nd Direct Hot-Stamped/Die-Quenched Product Mechanical Requirements” table. If the hardness is converted from one scale to another, the conversions in ASTM E140 shall be used. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or ne
29、tworking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16579 Copyright 2012 General Motors Company All Rights Reserved May 2012 Page 3 of 7 3.7.3 Mechanical Properties. The mechanical properties of the part shall be evaluated by machined tensile bars taken from flat se
30、ctions of the part. Note: Due to the high strength and difficulties in machining post heat treated boron steels, the use of a water-jet cutting is recommended. Any metallic pre-coatings such as aluminum-silicon (AS), zinc (HD), galvanneal (A) or zinc/nickel (EG N) shall be left on the sample for tes
31、ting and determination of thickness. In the case where part size and/or shape are not conducive for the removal of conventional tensile bar sized samples, sub-size standard tensile bars shall be used as described in ASTM E-8. 3.7.4 Coating Thickness. The coating thickness shall be evaluated in the s
32、ame or similar areas used to measure hardness with samples cut perpendicular to the panel surface. Conventionally mounted samples shall be used to evaluate the cross sectional thickness of coated parts before and after heat treatment. This analysis shall include measurement of the total thickness of
33、 the coating as well as of the transition layer between the coating and the steel. Optical photos of the coating and the transition layer shall be taken at 500x and 1000x and any other magnification that properly shows the coating and the alloy layers. The magnification and a reference line shall be
34、 included on all photos to enable thickness estimation at a later date. When using a metallurgical microscope, standard mounting practices shall be used and thickness shall be measured at 500x magnification. If parts are mechanically cleaned or media blasted to remove the oxide coating, coating thic
35、kness shall be measured after the blasting operation. 3.7.5 Bend Test for Base Metal Cracking. Bend testing is required for steel supplier qualification. Testing shall be performed according GMW14400. PHS stampers may also use this test to ensure quality of their steel supply source and part perform
36、ance. 3.7.6 Coating Analysis. Suppliers shall verify, through microscopic evaluation, that the manufacturing process is capable of producing parts that are free of surface discontinuities in the coating and surface of the steel that could negatively affect part performance such as, but not limited t
37、o; liquid metal embrittlement (LME), coating cracks, loss of coating adhesion, etc. An example of LME is shown in Appendix A, Figure A1. 3.8 Sample Report. The supplier shall compile the information gathered from testing paragraphs 3.7.1 thru 3.7.7 for review by the GM Global Purchasing and Supply C
38、hain (GPSC) Supplier Quality. The report shall be compiled following the same order of testing detailed in this section. Each page shall be numbered and the title of each page shall use the appropriate paragraph number and heading used in paragraphs 3.7.1 thru 3.7.7. The report shall include tables
39、that summarize the compiled data and any appropriate photomicrographs of the microstructure, coating thickness and the bend test results and is considered a requirement for the part PPAP documentation. 4 Manufacturing Process 4.1 Heat Treatment/Ovens. Suppliers shall develop control plans for the ma
40、intenance of proper oven temperature, part soak times and furnace dew point as required to meet the quality needs of the material and part being processed. For uncoated materials, the furnace atmosphere may need regulation to minimize oxide formation. Transfer time from furnace to die shall be consi
41、stent with manufacturers guidelines and established process control plans such that all specification and part requirements are met. 4.1.1 Manufacturers shall measure and record the temperature of parts prior to die closing and upon die opening with “on-line” infrared gauges or preferably, thermal i
42、maging equipment. The process shall be run within pre-established temperature ranges. Parts produced during periods outside of established control requirements shall be either discarded or quarantined until they can be evaluated to ensure conformance to all requirements of GMW14400. 4.1.2 For coated
43、 steels, the ovens shall be operated such that the total coating weight and thickness of alloy layer(s) in the finished part are within specification requirements as shown in GMW14400 and any requirements on the engineering drawing/math release. 4.1.3 The supplier shall develop control plans for min
44、imum and maximum times that parts can remain in the oven and provide proof that their process will guarantee that any excursions from these requirements are identified, corrected and that those parts will be disposed of and prevented from entering the supply stream. 4.1.4 As is appropriate for the m
45、aterial and coating being processed, suppliers shall maintain proper controls of furnace atmosphere and soak times such that surface oxides are minimized and the base metal is not rendered sensitive to post process cracking or environmental cracking during its service life. Suppliers shall maintain
46、their processes such that cracks within the coating are minimized. Break-offs or burn-offs of the coating caused by the stamping process are not allowed. Cracks within the coatings must be minimized by the Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot
47、for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16579 Copyright 2012 General Motors Company All Rights Reserved May 2012 Page 4 of 7 supplier as much as possible. If cracks occur in zinc based coatings, crack width shall be less th
48、an the coating thickness and shall not affect corrosion protection. Examples of these coating defects are shown in Figures A2 thru A4 in Appendix A. 4.2 Hot Stamping. The hot stamper shall be responsible to either develop their own dies or to work with reputable, experienced and established die sour
49、ces to produce dies that have sufficient cooling capacity to produce parts with the required microstructure, hardness, coating thickness, mechanical properties and part performance as required by GM. 4.2.1 The supplier shall verify that after heat treatment and stamping, that the parts meet all requirements established by GM. The supplier shall verify on formed and quenched parts that the established process produces parts that are within the minimum and maximum re
