Limits of IATF implementability based on the example of heat-treatable steel for cold rollers

Among other products, Salzgitter Flachstahl GmbH produces steel strip that is frequently used as feedstock for components in the automotive industry. Certification in accordance with international quality rules is a precondition. SZFG has been certified since 1990, and the requirements of the International Automotive Task Force (IATF) were successfully evidenced and documented in summer 2019 in the context of a comprehensive LRQA audit.

The IATF is a work group consisting of a number of OEMs (VW, Daimler, BMW, Fiat Chrysler US, PSA, Ford, General Motors, Fiat Chrysler Italy and Renault), as well as five national associations (ANFIA, AIAG, FIEV, SMMT and VDA), tasked with standardizing and extending the globally applicable QM requirements of IATF 16949. This applies especially to Section 1.1 Scope of application – additional conditions for ISO 9001: 2015 under which the application of this QMS standard is required “for the entire delivery chain”.

Along with the mild and structural steels available worldwide, micro-alloyed grades as well as case-hardened steel and tempered steels are produced every day in the Salzgitter steelworks. Virtually no order is completed to standard requirements, but is agreed with the individual customer instead (analysis range, mechanical properties, geometries, surfaces etc.).  

Due to their good processability and exceptional wear resistance after tempering, our case-hardened steel and tempered steels are used almost exclusively in engine and transmission components, as well as for chassis parts. There is therefore a direct link with the requirements of IATF 16949.

As IATF standards pertain to components and component assemblies, their requirements are naturally not without adjustments to be applied to the feedstock and semi-finished material. Implementation encompassing the entire process and supply chain (e.g., right through to ore suppliers) is not possible. For instance, tens of thousands of individual parts are produced from one Salzgitter Flachstahl slab and its around 25 t hot strip (average coil weight for cold rollers) in the downstream processes at the automotive supplier. 

Based on analysis ranges that are agreed with the customer and that are a great deal more stringent than under the customary norms, Salzgitter Flachstahl produces around 250 mm thick slabs. These are transported to the next step down the line, i.e. to the hot rolling mill where they are pushed into the reheating furnace at between 350 – 450 °C.  Rolling out to customer specification takes place in the reversing roughing train and the 7-stand finishing section. The wound strip is then delivered to the cold roller as coils. The cold roller reduces the strip thickness to customer specification, along with the agreed surface and inner quality. With clutch plates, for instance, a very high precision plane parallelity is required for which Salzgitter Flachstahl’s hot strip profiles provide an excellent basis.

Hot strip products as semi-finished material and feedstock for manufacturing products and components for the automotive industry have a relatively short life span as the life cycle of the product delivered may already be terminated upon unwinding the coil or the split backing strip. The properties in the delivered condition undergo a partly huge transformation in downstream processes. Consequently, the IATF requirements are only applicable to the chemical composition (for safety components, D parts, A parts etc.).

Initial orders are always produced on production lines with serial processes independently of the customer and the intended use. Prototypes or laboratory material are excluded. The initial sample test report required under Section 8.4 of the IATF is therefore no longer applicable, and the transition to serial production is documented by the customer through subsequent orders.

Initial sampling may well be expedient for prototypes in order to avoid complex testing before being ready for serial production but cannot be applied to the hot strip products of Salzgitter Flachstahl. At Salzgitter Flachstahl, all samples/prototypes are produced on production lines under standard production conditions. Upfront laboratory production is not possible as a rule. In place of an initial sample test report, a 3.1 inspection certificate (DIN EN ISO 10204) is sufficient for documenting the production process and specification-compliant production. Processing can take place on different facilities (e.g., furnace, converters, casting systems, reheating furnaces prior to rolling, coilers, pickling lines etc.). Verifying potential variations in series production through individual product testing is not possible.

The appointing of a Product Safety & Conformity Representative (PS/PCR) within the meaning of a ready-to-install end product is not possible for semi-finished products, since Salzgitter Flachstahl is not familiar with and is unable to influence the requirements and the further processing of the material. A PS/PCR (Product Safety & Conformity Representative) within the meaning of IATF 16949 cannot be appointed by the steel producer as the requisite knowledge of the entire production process for a product, including the design fundamentals and the specific requirements placed on the component, are not known and are largely subject to confidentiality. 

In the summer of 2019, Salzgitter Flachstahl successfully completed a one-week control audit by the certifying body Lloyds Register GmbH and its three IATF auditors. The focus of the process was placed on the value-added processes of pig iron production, slab production, hot strip and cold strip production, as well as other value conserving processes, e.g., production logistics & customer logistics, order processing & production planning, along with personnel management and procurement.