The Effect of Bismuth on Technological and Material Characteristics of Low-Alloyed Automotive Steels with a Good Machinability

Metals

Ondřej Kotásek¹  Vladislav Kurka¹  Zdeněk Kuboň¹  Ladislav Kander¹  Petr Jonšta¹ 

[1] MATERIAL AND METALLURGICAL RESEARCH Ltd., Pohraniční 693/31, 703 00 Ostrava, Czech Republic;

关键词: low-alloyed automotive steel;    bismuth;    steelmaking;    forging;    microstructure;    mechanical properties;   

DOI  :  10.3390/met12020301

来源: DOAJ

【 摘 要 】

The aim of this work is to compare the technological and material properties of CMnCr steels without bismuth, with 0.08 wt. % Bi and 0.12 wt. % Bi. Experimental heats showed that the most advantageous alloying of Bi into the heat was in the ladle, with an efficiency of about 20%. The optimal temperature range for forming steel was found to be 1160–1050 °C. With increasing Bi content, the formability of steels and plastic properties decreased, while the yield stress and tensile strength increased. Manganese sulfides, aluminum oxides, or oxysulfides, which were segregated both individually and in clusters, were found in the matrix of all tested steels. In steels with Bi, the Bi particles segregate the separately in the form of globules, either as envelopes of elongated MnS or Al₂O₃ particles segregated in rows. Sulfur dot-shaped segregations in the steel with 0.12 wt. % of Bi and the steel without Bi were essentially uniform over the whole area. For the steel with 0.08 wt. % of Bi, both dot-like and ray-ordered sulfur segregations were observed. The microstructure of all tested steels was ferritic–pearlitic with islands of bainite. Towards the center of the forged bars, variable shape and size of bainite blocks were observed. Machinability tests evaluated by the extend of tool wear showed that the most advantageous was CMnCr steel alloyed with 0.08 wt. % Bi.

【 授权许可】

Unknown