Quenched and tempered steels

Quenched and tempered steels obtain their application properties through austenitizing, quenching and tempering. They cover a minimum tensile strength range of around 470 to 1250 N/mm² in the quenched and tempered condition. In addition to good tensile strength, they are also characterized by high yield strength and ductility. The properties in the final state should be as homogeneous as possible across the cross-section. Compared to quality steels, stainless steels not only have lower phosphorus and sulphur contents but also more uniform properties, for example after heat treatment.

Single-bar heat treatment enables the highest quality and optimum utilization of the material potential through controlled adjustment of the microstructure and steel properties bar by bar. This leads to homogeneous mechanical properties across the entire bar and batch, meets the strict requirements of the automotive industry and exceeds the possibilities of coil tempering. Coil tempering harbors risks such as high scattering of steel properties and uneven microstructure formation, which can lead to failure and recalls in safety-relevant components. Single-bar tempering minimizes these risks and guarantees precise and consistent quality.

In addition, single-bar heat-treated steel meets the high requirements of the automotive industry, which are constantly increasing due to stricter DIN tolerances and standards. Steel bars are tempered on the XTP® system in accordance with CQI-9.

Precision adaptation for tightened tolerances in automotive and mechanical engineering

The solution to meet tightened tolerances in automotive and mechanical engineering is the inductive single-bar heat treatment. In this method, each bar undergoes heat treatment individually, ensuring uniform heating and consistent mechanical-technological steel properties. Swiss Steel Group employs modern technology, including laser monitoring for feed speed, to prevent technical defects and maintain consistently high steel quality. A database stores all relevant process parameters, and the in-house material laboratory optimizes technological settings for new or modified steels to achieve the required microstructures and mechanical properties.

We use support tables of up to 13 meters in length to feed bars individually into the process. This enables bars with lengths of 2.80 meters up to 13 meters to be processed on the system. The dimensions of the coils for induction heating are adapted to the bar steel diameter, whereby three different dimension ranges from 15 to 80 millimetres can be selected. This adaptation achieves a high level of efficiency, as the non-contact heating of the steel becomes more effective. This increases the energy efficiency and precision of the tempering process, which in turn improves the quality of the steel.

Innovation in quenching and tempering for optimum steel properties

We also offer uniform quenching and tempering of tubes, in which two tube lifters remove the quenching medium from the tubes to ensure homogeneous microstructures, properties and straightness of the steel tubes. The pressure in the ring nozzles, which quench the steel after tempering, is regulated by flow monitors. Tempering is then also carried out inductively. It is possible to quench the steel bars evenly and selectively in order to positively influence the steel properties and prevent hardening distortion. This process is low in decarburization and scaling and ensures uniform heat treatment.

Some materials tend to form flakes at the end of the bar. In the worst case scenario, these can damage tools or test probes during further processing. To avoid this risk, we offer the option of automatically cutting off the start and end of each bar directly after the individual bar tempering process. Finally, the bars are collected in bundles to protect the material.

Wire rod

• untreated
• thermomechanically treated

Steel bars

must meet high requirements in terms of straightness and freedom from surface or internal defects.

• untreated
• normalizing rolled
• straightened / separated
• crack-tested
• ultrasonic-tested
• demagnetized
• verified against confusion