Stahlinstitut VDEh https://vdeh.de/en/standardisation/stahl-eisen-blaetter/recently-published-sheets/ – 21.12.2024

This first part of the series of SEP 1220 specifications contains general requirements. It is meant as a basis for unified material characterization and shall standardize the exchange of data between the materials suppliers and customers.

Described are the characterization of the base materials, location of sampling, general test conditions, including recommendations for cyclic testing. The data format for data exchange of tests (data header) is explained in detail.

When developing new materials before they are launched on the market as part of the material approval process the steel producers prove not only the basic material characterisation, but also the processability in terms of joining technology. The reason for this is the requirement for compatibility with the entire further processing process. In the past these tests were carried out according to the specifications of the individual automobile manufacturers. This resulted in a large and cost-intensive test effort which significantly delayed the introduction of new steels and made them unnecessarily expensive.

For this reason the Stahl-Eisen-Prüfblatt (SEP) 1220 was developed and published in 2011 in which the material approval process is described with regard to the joinability. The aim was to create a standardised approval procedure which is recognised by steel manufacturers and users, not only to accelerate the introduction of new materials, but also to simplify the provision of data and the comparability of test results. Part 1: General specifications, Part 2: Resistance spot welding, Part 3: Laser beam welding and Part 4: MIG-brazing were published with the issue date 8.2011.

The 1st edition of Part 5: Gas Metal Arc Welding (GMAW) could now be published with issue date 12.2020. The test methods specified in this Stahl-Eisen-Prüfblatt (SEP) are used to determine the suitability of steel sheets for the joining process of gas-shielded metal arc welding (process ISO 4063:135).

The Stahl-Eisen-Prüfblatt (SEP) 1220 describes methods for determination of the joinability of steel sheets without / with surface coating and the documentation of the results. It is meant as a basis for standardised material characterisation by welding, brazing, mechanical joining and adhesivebonding and is intended to standardise the exchange of data between material suppliers, car manufacturers and their suppliers. The SEP 1220 specifies the requirements for implementation. The joinability is assessed by the user based on the results of the joining test and documentation guideline and the specific application.

The basic structure of an SEP for the material approval process of joinability includes both the shape specimen and specimen preparation, the test methods and test conditions used as well as specifications for the experimental procedure up to the subsequent documentation of the test data. However, the results are not evaluated as this should be done depending on the particular application and the user.

In the framework of collaborative work between automotive and steel industries, for the introduction of newly developed steel grades into serial application in automotive production, phases of the material approval process were defined.

A material approval process shall be used to specify the necessary steps for qualification of new grades of thin steel sheets through to readiness for use in series (volume) production. In order to evaluate new steel grades regarding their fitness for use in automotive series production, a test matrix is provided for supplying a broad data base. The results of testing are necessary requirements for the approval of a steel grade by the customer (OEM).

SEW 550 covers steels predominantly used for mechanical engineering purposes, which are used to produce larger open die forged components in the quenched and tempered or normalised condition. (SEW 555 applies for energy technology).

The first edition of SEW 550 was published 1951, followed by editions 1957 and 1976. Afterwards, ISO 683-2 and EN 10250 were developed which have different steel grades and material properties compared to SEW 550. The wall thickness range is between 160 and 750 (1000) mm.

SEW 550 specifies the chemical composition, sampling, mechanical properties (in sample locations L, T and Q) as well as testing and documentation. Annex A provides formulae to calculate the relevant heat treatment diameter. New in SEW 550 is the hardenability criterion. Compared to the 3rd edition 1976, 7 steel grades were added and 2 removed. This SEW is available for the first time in English translation.