Research on Welding Process of Low Alloy High Strength Steel 20MnTiB

Abstract

In this paper, the properties of the base metal of the low-alloy high-strength steel 20MnTiB, the welding process and the microstructure and properties of the welded joints were studied. The results are as follows: post-heat treatment below 400°C, the strength change of the steel decreases slowly, the elongation does not change significantly, and the metallographic structure is not obvious. When the temperature is above 400, the strength is greatly reduced. And its plasticity increases remarkably, and precipitates on the grain boundary are precipitated and grown on the metallographic structure. When the line energy is in the range of 9.6~12.0kJ/cm, the mechanical properties and microstructure of the welded joints meet the requirements, and the welding process that meets the requirements is studied. Finally, the mechanical properties and microstructure of the welded joint are studied. Provide a reference for the research and application of steel.

Effect of Mg Addition on the Microstructure and Properties of a Heat-Affected Zone in Submerged Arc Welding of an Al-Killed Low Carbon Steel

“…Moreover, with the welding heat input increased from 29.55 to 44.11 kJ/cm, the number of GBF increases. In FGHAZ, although austenite phase transition happens during the welding process, the peak temperature is not as high as CGHAZ, and austenite grains coarsening may not appear significant as CGHAZ [ 1 ]. In the subsequent cooling process, fine equiaxial ferrite grains and a small amount of pearlite are formed, as shown in the microstructure ( Figure 7 c,g).…”

“…Thus, it is believed to have negative effect on promoting the nucleation of inclusion-induced AF when the cooling rate is too high or too low. In the real welding thermal cycle procedure, the peak temperatures of both FGHAZ and ICHAZ are all (<1200 °C) significantly lower than that of fusion zone and CGHAZ [ 1 ]. It is thus speculated that the reason for the insignificant AF nucleation in these two regions is the cooling rate, which may be not suitable for AF nucleation.…”

“…With the demand for both ship plate thickness increments and welding cost reductions, higher input energy is crucial to improve the welding efficiency, which in turn puts higher requirements on the weldability of the plate steels. Normally, the heat-affected zone (HAZ) from the weld joint to the base metal includes a fusion zone, coarse-grained heat-affected zone (CGHAZ) with a thickness of about 1.5 mm, fine-grained or recrystallization heat-affected zone (FGHAZ) with a thickness of about 1.0 mm, and an intercritical heat-affected zone (ICHAZ) with a thickness of about 2.0 mm [ 1 ]. The CGHAZ is very close to the weld seam with high peak temperature and obvious coarsening of the prior austenite grain size during welding, which often becomes the weakest zone of the ship plate steel and seriously affects the service reliability [ 2 ].…”