Tensile Behavior of Cast and Electron Beam Welded Interstitially Strengthened High-Alloy TRIP Steel

Abstract

Due to their enormous potential for energy absorption, high-alloy TRIP/TWIP steels are designed to fulfill contrary requirements of crash-relevant structures such as strength, toughness, and ductility and even excellent weldability. To further optimize these mechanical properties and reduce the production costs at the same time, high-alloy TRIP/TWIP steels with an increased content of carbon and nitrogen and decreased amount of nickel are produced. The mechanical properties of the base materials and the capability for the phase transformation are determined for different temperatures (À40 to þ60 8C) in quasistatic tensile tests. In comparison, welding experiments with an electron beam are performed and the microstructure is examined via light optical microscopy. The welded sheets are also tested and the mechanical properties determined via micro-hardness measurements and quasistatic tensile tests. While a TRIP effect is noticeable during loading at room temperature, optimal properties of the base material can be achieved at temperatures below 0 8C. The welded samples show a ferritic-austenitic microstructure and solidified as primary ferritic with joint austenite and ferrite formation in the solidification interval.

The Microstructure and Mechanical Behavior of TRIP 800 and DP 1000 Steels Welded by Electron Beam Welding Method

“…Thus, it can be said that soften zones affected the tensile strength of the joinings. observed no significant influence on the mechanical properties (tensile strength and elongation) of electron beam welded metal compared to the base metal [19]. On the contrary, in this present study, it was seen that the highest tensile strength (averagely 840 MPa) and elongation (averagely 23%) values were observed at the TRIP 800-TRIP 800 welded joint.…”

“…High Ni rate decreased both FZ and HAZ [28]. Various researchers reported that slower welding speeds caused homogeneous hardness profile between FZ and base metal at TRIP steel welded by using EBW [19]. However, in the present study, the welding speed was slower than the study mentioned above (the speed in the present study is approximately 3 mm/s slower than theirs) and heterogeneous hardness patterns were observed at the base metal and FZ.…”

“…There are studies in the literature reporting the weldability and post-weld strength values of DP steels and TRIP steels with welding methods such as gas metal arc welding (GMAW) [13,14], laser beam welding (LBW) [15,16] and resistance spot welding (RSW) [17,18]. There is some studies about advanced high strength steels are used at automotive industry welded by EBW [19][20][21]. However, no studies regarding the welding of DP or TRIP steels by using EBW were found in the literature.…”