In concert with the repairer’s right to repair information, GM has issued the Recommended GM Steel Reparability matrix, a chart that identifies GM’s repair recommendations according to the type of steel that the part is made from. The matrix contains information on the steel identification stamping symbols, steel grade, GM specifications, recommended welding methods, cold reparability, use of heat for repairs, the temperature range that should be used, and the maximum heat allotment. The second page of the matrix is a chart of Descriptions of GM Steel. 

The Recommended GM Steel Reparability Matrix can be found free at www.techinfo.gmgoodwrench.com. Before entering the site, you must accept the “Terms of Use,” which states that you agree to only download or print off one copy of the procedures for your use. Adobe® Acrobat Reader® is required to view the information on this site. From the top of the home page, select the Tech Info link. Then select the Steel Reparability Matrix file from the list on the Technical Information page.

Matrix columns

There are eight main columns in this matrix. The first three columns are used to explain the type of steel that is being referenced. The first column identifies the steel ID stamping symbol or International Organization for Standardization (ISO) symbol for the steel. The second column identifies the grade of steel, such as mild, laminated, dual phase, or boron steel. The third column is used by the steel companies to identify the GM specification for the type of steel.

Column four identifies whether or not certain types of welding are recommended including GMA (MIG) welding, squeeze-type resistance spot welding (RSW), and MIG brazing. It is stated in footnote number one that when MIG brazing is recommended, slotted holes 8 x 16 mm should be used. For some steels, like DP>800, UHSS, martensitic, boron, and TRIP, it is noted that GMA (MIG) plug welds are the only type of GMA (MIG) welding that is recommended. The footnote stresses that these steels should not be stitch welded during repairs, nor used as a backer for stitch welding. It is noted that “Deviation from this chart is only allowed if there has been a crash analysis completed by the Design Engineer and a service procedure has been written.”