Changes of microstructure and mechanical properties of the HAZ of the S960MC steel sheet weld joint

Abstract

The TMCP (thermo-mechanically controlled processed) steels belong to the group of ultra-high strength steels, which exhibit exceptional combination of high tensile and yield strength, toughness and ductility. These steels were introduced in the heavy machinery constructions, such as heavy mobile cranes, chassis trucks and other to reduce their weight, what increases their loading capacity and ecology of transport. The high tensile and yield strength of this type of steels is obtained by the combination of the chemical composition, heat treatment and the mechanical processing. However, the heat input into the material during the welding significantly affect properties of the steel and the whole joint. In this paper are presented results of mechanical properties evaluation and structural analysis of the welds of the thin sheets made of the S960MC steel, which were welded using the GMAW procedure. The microstructural evaluation referred significant changes in the HAZ. This area contains the three sub-zones, coarse grain (CGHAZ), fine grain (FGHAZ) and intercritical zone (ICHAZ). Analysis of microhardness and the tensile tests results showed, that ICHAZ is the most critical area of the whole welded joint.

Behavior of Weld to S960MC High Strength Steel from Joining Process at Micro-Jet Cooling with Critical Parameters under Static and Fatigue Loading

“…This kind of specimen was also very sufficient at determining the influence of a control signal as displacement, stress, and strain. Literature [ 17 , 19 , 20 ] indicates mechanical properties of weld for S960MC without any details on a specimen shape and dimensions [ 17 , 20 ] or presents a bigger specimen, i.e., having 1000 mm length [ 19 ]. As it was obtained, the steel tested was not sensitive to the signal type used.…”

“…Moreover, the technique is very typical; nevertheless, some differences between welded regions can be easily indicated [ 18 ]. This type of results enables to follow concludes on the quality of joint if sufficient numbers of measurement regions are collected [ 20 ]. This approach can also be evidence in [ 17 , 21 ], which presents data from micro-hardness tests [ 17 ] on the joint manufactured at the Gas Metal Arc Weld (GMAW).…”

Microstructural evaluation of welded joints of ASTM Mar-M247 superalloy using ERNiCrMo-3 filler alloy

“…These morphology transformations and irregular distribution of the γ' phase are concentrated in the closer region of the fusion line. These changes in the HAZ rely on the amount of thermal exposure and cooling rate during the welding process [35,36]. At elevated-temperatures, MC carbide can interact with the matrix phase γ to form new depositions of M 23 C 6 carbides.…”

Structure and Mechanical Properties of High Strength Steel 960QL Weldments

“…The choice of a suitable chemical composition and heat treatment allows production of steels with yield strength up to 1300 MPa, elongation up to 10%, and relatively high impact strength at low temperatures (even at -60°C). High-strength steels have a low carbon and microalloying elements (Ti, V, Nb or Al) content, and this results in a low value of carbon equivalent (CE), and hence good weldability [4,5,6,7,8]. High-strength steels possess fine-grained structure, usually consisting of martensite and bainite [9,10].…”