Abstract

The addition of rare earth element Ce in ferritic stainless steel can improve the high temperature performance to meet the service requirements of automobile exhaust systems at high temperatures. Automobile exhaust systems are generally applied as welded pipes, so it is necessary to study the effect of Ce on the weldability of ferritic stainless steel. In this study, the Trans-varestraint test method was used to test the solidification crack sensitivities of 441 and 441Ce ferritic stainless steel. The 441Ce steel, which has added Ce, showed poor resistance to weld solidification cracking. Using Thermo-Calc software, Ce was observed to expand the solidification temperature range of 441 ferritic stainless steel, increase the time for solid–liquid coexistence during solidification, and increase the sensitivity of solidification cracking. Further, from scanning electron microscopy and energy dispersive spectrometer analysis, the addition of Ce was found to reduce high temperature precipitation (Ti,Nb)(C,N), reduce or even eliminate the “pinning” effect during solidification, and increase solidification crack sensitivity of 441 ferritic stainless steel.

Highlights

  • As an important type of stainless steel, ferritic stainless steel has been a popular focus of research and application in recent years, because of its lack of nickel content and because it is economical

  • Saturation strain refers to the strain that significant change; the maximum crack distance (MCD) refers to the maximum crack length (MCL) measured for each value of exceeds the threshold value where the maximum crack length no longer shows a significant change; the test strain above the saturation strain

  • The sensitivity ofCe; the solidification crack of 441 ferritic stainless steel can be improved by adding the rare earth element

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Summary

Introduction

As an important type of stainless steel, ferritic stainless steel has been a popular focus of research and application in recent years, because of its lack of nickel content and because it is economical. Rare earth elements have a unique electronic layer structure and active chemical properties. In stainless steel, they can clean the steel, metamorphose inclusions, control solidification structure, and refine the grain [8,9,10,11,12], so they have received much attention from scholars these days. Some scholars have shown that the addition of rare earth elements in ferritic stainless steel can improve its corrosion resistance, mechanical properties, high temperature performance, and other service properties [13,14,15,16].

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