Study of Solidification Cracking Susceptibility during Laser Welding in an Advanced High Strength Automotive Steel

Abstract

Susceptibility to weld solidification cracking in transformation-induced plasticity steel sheets was studied using a modified standard hot cracking test used in the automotive industry. To vary the amount of self-restraint, bead-on-plate laser welding was carried out on a single-sided clamped specimen at increasing distances from the free edge. Solidification cracking was observed when welding was carried out close to the free edge. With increasing amount of restraint, the crack length showed a decreasing trend, and at a certain distance, no cracking was observed. With the aid of a finite element-based model, dynamic thermal and mechanical conditions that prevail along the transverse direction of the mushy zone are used to explain the cracking susceptibility obtained experimentally. The results indicate that the transverse strain close to the fusion boundary can be used as a criterion to predict the cracking behavior. The outcome of the study shows that optimum processing parameters can be used to weld steels closer to the free edge without solidification cracking.

Effect of weld travel speed on solidification cracking behavior. Part 2: testing conditions and metrics

“…ratio decreased when speed increased). Faster welding speed was associated with a decrease in solidification cracking susceptibility ( Figure 5) [33]. This drop in cracking has been associated with smaller thermal strains generated during welding at faster travel speeds ( Figure 5b) [33].…”

“…Such metallurgy-speed interaction is also true for MIG and MAG welding processes, and therefore care must be taken in generalizing conclusions. f. Example 6 The welding speed effect on solidification cracking was investigated using the free-edge weldability test [33,34]. Autogeneous laser welds were performed on TRIP steels using 1100 W and varying speed from 9 to 12 mm•s -1 (i.e.…”

“…Faster welding speed was associated with a decrease in solidification cracking susceptibility ( Figure 5) [33]. This drop in cracking has been associated with smaller thermal strains generated during welding at faster travel speeds ( Figure 5b) [33]. g. Example 7 Solidification cracking susceptibility was investigated in autogenous laser welds of Type 304 stainless steels using the preloading tensile strain (PLTS) cracking test [22].…”

“…Measurements on autogenous laser beam welds of TRIP steels: (a) crack length as a function of welding speed and restraint conditions (distance from free edge); (b) thermal strain variation with welding speed[33].…”

Liquation Cracking Tendency of Novel Al-Mg-Zn Alloys with a Zn/Mg Ratio below 1.0 during Fusion Welding

“…Poor weldability has prevented their adoption in long-span material application scenarios. Most studies have been carried out on the solidification cracking behavior of metal materials [3][4][5]. These solidification cracks usually take place at the end of the solidification process, during which time solid phases occur as the temperature cools down, and grains begin to contact with their neighboring ones.…”