Status of the standardized material release process to assess the joining suitability of steel sheets

Ensuring the joining-related processability of a material throughout the entire process chain is extremely important to our customers. Consequently, this needs to be examined during the development of new steel materials even before the market launch. This step is already carried out at the steel producer in the framework of the material release process.
Until now, these examinations have been conducted in accordance with specifications which often differed only slightly from one another, such as the specimen geometry or the welding parameters of the OEMs. This results in a major, cost-intensive testing effort which hinders the swift introduction of new steels. The objective was therefore to create a steel and iron test sheet (SEP for Stahl- und Eisenprüfblatt) in which the material release process for joining is standardized. The testing methods necessary for the joining process were specified in steel-iron test sheet SEP1220-ff (Testing and documentation guideline for the joining suitability of thin sheets made of steel). This includes the experimental procedure on the one hand and the documentation of the results all the way through to the data transfer format on the other. This was carried out in cooperation between VDA (Verband der Automobilindustrie) and VDEh (Stahlinstitut Verein Deutscher Eisenhüttenleute).
“Steel and iron test sheet (SEP) 1220 is divided into various sections. The first part (SEP1220-1) contains the general agreements on material characterization, while the following sections specify the execution of the tests depending on the various joining methods. Figure 1 gives an overview of the individual parts and the current processing status.

Taking resistance spot welding as an example, Figure 2 shows the tests to be conducted depending on the various stages in the material release process.

Not only are OEMs and steel producers using the agreements reached here on examining the suitability for joining, the testing methods described in SEP1220 are also already being used in the area of publicly funded research. This standardized process is accepted by all the parties involved and replaces the individual release according to the particular internal standards common in the past while accelerating the material release process. The comparability of the results between the OEM, its suppliers and the steel producer is moreover simplified by the coordinated testing methods. This allows customers to select materials at an earlier point in time during the body development. In this way, characteristics packets allocated to the Salzgitter Flachstahl GmbH sheet metal materials are provided for assessing the joining-related processability.