Manufacturing of 42SiCr-Pipes for Quenching and Partitioning by Longitudinal HFI-Welding

Abstract

In the pipe manufacturing and pipe processing industry, the demand for cost-effective pipes with high strength and good ductility is increasing. In the present study, the inductive longitudinal welding process was combined with a Quenching and Partitioning (Q&P) treatment to manufacture pipes with enhanced mechanical properties. The aim of the Q&P process is to establish a martensitic structure with increased retained austenite content. This allows for the beneficial use of both phases: the strength of martensite as well as the ductility of retained austenite. A 42SiCr steel, developed for Q&P processes, was joined at the longitudinal seam by a high-frequency induction (HFI) welding process and was subsequently heat-treated. The applied heat treatments included normalizing, austenitizing, quenching, and two Q&P strategies (Q&P-A/Q&P-B) with distinct quenching (Tq = 200/150 °C) and partitioning temperatures (Tp = 300/250 °C). Investigations of the microstructures revealed that Q&P tubes exhibit increased amounts of retained austenite in the martensitic matrix. Differences between the weld junction and the base material occurred, especially regarding the morphology of the martensite; the martensite found in the weld junction is finer and corresponds more to the lath-type morphology, compared to the base material in the circumference. In all zones of the welded tube circumference, retained austenite has been found in similar distributions. The mechanical testing of the individual tubes demonstrated that the Q&P treatments offer increased strength compared to all other states and significantly improved ductility compared to the quenched condition. Therefore, the approach of Q&P treatment of HFI-welded tubes represents a route for the mass production of high-strength tubular products with improved ductility.

Experimental Analysis of the Stability of Retained Austenite in a Low‐Alloy 42CrSi Steel after Different Quenching and Partitioning Heat Treatments

“…Martensite start (M S ) and martensite finish (M F ) temperatures as well as the A c3 temperature of the material can be found in literature. [ 26–29 ] These temperatures were about 300, 180, and 845 °C, respectively. The 42CrSi steel represents a modification of materials widely used in the automotive sector, in particular for the production of transport vehicle components.…”

Improving the Energy Efficiency of the Production of Pipes Welded with High-Frequency Induction

“…Poorer quality can lead to huge losses and create life-or health-threatening situations. Therefore, HFI welding processes must be designed very precisely so that the weld does not have any discontinuities (defects) [17,18].…”

Localized Induction Heating of Cu-Sn Layers for Rapid Solid-Liquid Interdiffusion Bonding Based on Miniaturized Coils

“…Another field of induction-based joining is the longitudinal welding of pipes from advanced high strength steels (AHSS) by high-frequency induction welding. The authors demonstrated the longitudinal welding of 42SiCr- [33] and 34MnB5-pipes [34] in combination with subsequent heat treatments to manufacture pipes with enhanced mechanical properties.…”