Assessment of the Weldability of T-Welded Joints in 10 mm Thick TMCP Steel Using Laser Beam

Abstract

The article presents tests aimed to verify the possibility of Thermomechanically Controlled Processed (TMCP) steels T-joints laser welding. The 10 mm thick high-yield-point steel S700MC obtained in an industrial manufacturing process was used for tests of laser welding. The joints made during the tests were single- and double-sided. Subsequent nondestructive tests revealed that the laser-welded joints represented quality level B in accordance with PN-EN ISO 13919-1. Single-sided welding performed at the output laser beam power of 11 kW provided the penetration depth of just 8 mm without visibly deforming of the joint. The double-sided welded joints were characterized by proper geometry and the presence of gas pores in the welds not compromising the requirements of quality level B (strict requirements). The identified weld structure was bainitic-ferritic. The weld hardness was by approximately 60 HV1 higher than that of the base material (280 HV1). The HAZ (Heat Affected Zone) area was slightly softer than the base material. The tests of thin foils performed using a high-resolution scanning transmission electron microscope revealed that, during welding, an increase in the content of the base material in the weld was accompanied by an increase in contents of alloying microagents Ti and Nb, particularly near the fusion line. The above-named alloying microagents, in the form of fine-dispersive (Ti,Nb)(C,N) type precipitates, could reduce plastic properties of joints.

Laser Dissimilar Welding of AISI 430F and AISI 304 Stainless Steels

“…In addition, laser welding was initially considered unsuitable for difficult-to-weld materials and carried a high risk due to the concentrated heat source. A lot of research has been done on the possibility to use laser welding for joining various materials and show that this method makes it possible to obtain high quality welded joints using the wide range of conditions and parameters [ 29 , 30 , 31 ].…”

Underwater In Situ Local Heat Treatment by Additional Stitches for Improving the Weldability of Steel

“…As a method for improving the weldability of steel local heat treatment, provided by the heat from additional stitches, was chosen. Weldability tests are commonly used to evaluate the possibilities of the welding in the air for different materials [42,43], and in the water [35]. A Tekken weldability test was chosen for investigation.…”

Numerical Simulations of Laser and Hybrid S700MC T-Joint Welding

“…As provided by the producers and supplier, it also delivers exceptional weldability for fast and efficient processing. However, along with the change in the thickness of the welded elements, as well as the use of welding methods with a very sharp thermal cycle, unexpected problems are associated with the weldability of components made of this type of steel, as well as with the expected functional properties of the welded joints [21,24,29,30,35].…”

“…Another disadvantage of these modern heat sources is a relatively small efficiency. It is especially important if we also take into account the current energy problems of the world in which we live, as well as striving to reduce costs at every stage of the production process, wherever possible [15,16,17,18,19,20,21,22,23,24].…”

“…The comparison of the mentioned advantages and disadvantages of the classical (arc) methods of welding forces us to look for new solutions that combine the advantages of using high-density heat sources with methods that allow maintaining high strength and operational properties of modern and, therefore, more expensive construction materials. A certain solution to this problem, combining the advantages of laser welding while increasing the efficiency of the process is called hybrid welding (HLAW—hybrid laser arc welding) [24,25,26,27,28]. It consists of the use of two independent heat sources, such as a laser beam (most commonly a solid-state YAG laser) and an electric arc of the GMAW (Gas Metal Arc Welding) method.…”