Influence of forming temperature and partitioning on properties of steels for press-hardening

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F49777513%3A23210%2F22%3A43965181" target="_blank" >RIV/49777513:23210/22:43965181 - isvavai.cz</a>

Result on the web

—

DOI - Digital Object Identifier

—

Result language

angličtina

Original language name

Influence of forming temperature and partitioning on properties of steels for press-hardening

Original language description

To achieve better mechanical properties of steels used as car body reinforcement, thermomechan-ical processing of DOCOL PHS 1800 and DOCOL PHS 2000 steels for press-hardening was per-formed in the experiment. Both steels have approximately 0.003 mass content of boron in % to improve hardenability and thus increase strength and improve mechanical properties. The design of the processing regimes for all materials was based on previous tests to determine appropriate austenitization temperatures and times and ideal forming temperatures. The regimes were arranged according to the data measured in the industrial workplace and then gradually optimized. To transfer the results of laboratory tests into industrial practice, a tool with an omega profile was produced, which simulates the shape of a car body B-pillar. This tool can be heated up to 450 °C. It is therefore possible to form materials at different temperatures and, if necessary, to realize holding on the required temperature directly in the tool. The soaking at the austenitization temperature was performed in a chamber furnace. The austenitization temperature for DOCOL PHS 2000 was 860 °C, while for DOCOL PHS 1800 it was 940 °C. All materials were formed at three different temperatures (680 °C, 750 °C, and 800 ° C). At the same time, the transfer time was different for various shapes of semi-finished products (such as steel sheets or tubes). In the last step of the experiment, after forming, holding at the partitioning temperature was added to stabilize the microstructure and improve the mechanical properties, especially ductility. Specimens were taken from the formed specimens for mechanical testing, specifically for tensile test and hardness measurement. Metallographic analyzes were also performed on the specimens to observe the martensitic structure after the press-hardening process. The results of the analysis showed that by forming these materials by press-hardening it is possible to achieve a strength of over 1800 MPa for PHS 1800 steel and up to 2000 MPa for PHS 2000 steel. At the same time, there is an increase in ductility if the partitioning is included, but the ultimate tensile strength and yield strength decrease rapidly. Microstructural analyzes showed that in all cases a martensitic microstructure with a small proportion of bainite was obtained.

Czech name

—

Czech description

—

Type

O - Miscellaneous

CEP classification

—

OECD FORD branch

20501 - Materials engineering

Project

—

Continuities

S - Specificky vyzkum na vysokych skolach<br>I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2022

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů