scholarly journals Joining of ultra-high-strength steels using resistance element welding on conventional resistance spot welding guns

2021 ◽  
Author(s):  
Heinrich Günter ◽  
Gerson Meschut
Keyword(s):  
Spot Welding ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Single Step ◽  
Joining Technology ◽  
Joint Properties ◽  
Resistance Element Welding ◽  
Ultra High Strength Steels

AbstractSingle-step joining of dissimilar material combinations between ultra-high-strength steels and high-strength aluminium alloys with sufficient mechanical joint properties by using conventional resistance spot welding equipment has not been reported yet. In this research paper, a novel single-step joining technology, so-called self-penetrating resistance element welding, is introduced. First, the motivation for this novel joining technology, the state of the art in joining, and the process characteristics are presented. In the results section, the welding rivet geometry is first determined using forming simulations and validated by head tensile tests. Followed by the description of the welding process and its characteristics, the mechanical joint properties are reported. The results show that a numerically optimised welding rivet geometry can guarantee sufficient joint strength. By this welding rivet geometry, a thermally assisted penetration of aluminium and therefore welding to steel is possible with and without adhesive. Furthermore, it is shown that the welding process can be designed by means of simulations. Finally, the shear tensile tests prove that an overall sufficient joint strength is ensured.

Microstructural Evolution and Tensile Strength of Laser-Welded Butt Joints of Ultra-High Strength Steels: Low and High Alloy Steels

2021 ◽  
Vol 883 ◽  
pp. 250-257
Author(s):  
Mikko Hietala ◽  
Atef Hamada ◽  
Markku Keskitalo ◽  
Matias Jaskari ◽  
Jani Kumpula ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Fusion Zone ◽  
Microstructural Evolution ◽  
Laser Energy ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Butt Joints ◽  
Dissimilar Joints ◽  
Ultra High Strength Steels

The present study is focused on joining two ultra-high strength steels plates of 3 mm thickness using laser-welding. Abrasion resistant steel with martensitic structure, tensile strength (Rm) ≥ 2 GPa, and cold-deformed austenitic stainless steel, Rm 1.3 GPa, were used for the dissimilar butt joints. Two different laser energy inputs, 160 and 320 J/mm, were presented during welding. The weld morphology and microstructural evolution of the fusion zone were recorded using optical microscopy and electron back scattering diffraction (EBSD), respectively. The mechanical properties of the dissimilar joints were evaluated by hardness measurements and tensile tests. It was found that fusion zone has undergone a change in morphology and microstructure during welding depending upon the energy input. Analysis of the microstructural evolution in the fusion zone by EBSD examination showed that the presence of a mixture of small austenite grains in a matrix of martensite. The changes in hardness profiles and tensile strength under the experimental parameters were further reported.

Influences of Austenitization Parameters on Properties of Martensitic Stainless Steel in Hot Stamping

2014 ◽  
Vol 1063 ◽  
pp. 194-197
Author(s):  
Kai Wang ◽  
Zhi Bin Wang ◽  
Pei Xing Liu ◽  
Yi Sheng Zhang
Keyword(s):  
Stainless Steel ◽  
Martensitic Stainless Steel ◽  
Hot Stamping ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Compression Tests ◽  
Austenitization Temperature ◽  
Bare Steel ◽  
Ultra High Strength Steels

Due to high temperature and inevitable contact with air, strong oxidation and decarburization of the bare steel exist in hot stamping of ultra-high strength steels. Martensitic stainless steel could be a potential solution with its corrosion resistance and high strength. In this paper, the influences of austenitization temperature (850 to 1000 °C) and time (3 to 10 min) on final properties of 410 martensitic stainless steel were investigated, to obtain an ultra-high strength up to 1500MPa. The hot stamping of 410 steel is simulated by compression tests with a flat die. Mechanical properties of blanks after hot stamping process were detected by tensile tests. Results show that the final strength of 410 steel increases and the plasticity decreases, with the increase of austenitization temperature and time. After austenitization at 1000 °C for 5-10 min, an ultimate tensile strength up to 1500MPa is obtained with a martensite dominated microstructure.

Mechanical properties and microstructure of low carbon ultra-high strength steels (UHSS) microalloyed with boron

2012 ◽  
Vol 1373 ◽  
Author(s):  
I. Mejía ◽  
A. García de la Rosa ◽  
A. Bedolla-Jacuinde ◽  
J.M. Cabrera
Keyword(s):  
Mechanical Properties ◽  
Research Work ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Low Carbon ◽  
Advanced High Strength Steels ◽  
New Family ◽  
Ultra High Strength Steels ◽  
Hot Rolled

ABSTRACTThe aim of this research work is to study the effect of boron addition on mechanical properties and microstructure of a new family of low carbon NiCrVCu advanced high strength steels (AHSS). Experimental steels are thermo-mechanically processed (TMP) (hot-rolled+quenched). Results show that the microstructure of these steels contains bainite and martensite, predominantly, which nucleate along prior austenite grain boundaries (GB). On the other hand, tensile tests reveal that the TMP steels have YS (0.2% offset) of 978 MPa, UTS of 1140 MPa and EL of 18%. On the basis of exhibited microstructure and mechanical properties, these experimental steels are classified as bainitic-martensitic complex phase (CP) advanced ultra-high strength steels (UHSS).

scholarly journals Microstructure and Properties of Spot Welded Joints of Hot-Stamped Ultra-High Strength Steel Used for Automotive Body Structures

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 285 ◽  
Author(s):  
Zhixia Qiao ◽  
Huijun Li ◽  
Lianjin Li ◽  
Xiaoyu Ran ◽  
Liwen Feng
Keyword(s):  
Spot Welding ◽  
Mechanical Performance ◽  
High Strength Steels ◽  
High Hardness ◽  
High Strength ◽  
Resistance Spot ◽  
Automotive Body ◽  
Ultra High Strength Steels ◽  
Structural Parts ◽  
Spot Welded

Hot-stamped ultra-high strength steels have been widely used in automobile structural parts. Considering the high splash tendency in resistance spot welding due to their extremely high hardness, in this work, microstructural characteristics and mechanical performance of the resistance spot welded ultra-high strength steels are investigated. The results indicate that the interface between the nugget and heat-affected zone (HAZ) is the weakest zone where fractures initiate. In tensile shearing tests, a qualified spot welding joint failed with a button-shaped fracture. Welding defects would significantly decrease the load-carrying capacity and lead to interfacial fracture, except for a button-shaped fracture. In spot welding, it was found that a specific mid-frequency alternating current (AC) input mode, in which a 6 ms cooling cycle was inserted between every two neighboring current pulses, can avoid the splash in the spot welding of hot-stamped hardened steels.

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

2020 ◽  
Vol 65 (3) ◽  
pp. 113-123
Author(s):  
Miloš Mičian ◽  
Milan Maronek ◽  
Radoslav Konar ◽  
Daniel Harmaniak ◽  
Mihal Jambor ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Welded Joint ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Coarse Grain ◽  
Fine Grain ◽  
Microstructural Evaluation ◽  
Ultra High Strength Steels

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.

Resistance Spot Weldability of Hot-Formed Ultra High Strength Steel Based on Virtual and Physical Experiment

2015 ◽  
Vol 750 ◽  
pp. 244-250 ◽  
Author(s):  
Zhi Shui Yu ◽  
Wan Peng Dong ◽  
Chun Wei Ma ◽  
Jiang Wei Ren ◽  
Bi Hao Li ◽  
...  
Keyword(s):  
Spot Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Experimental Investigations ◽  
Tensile Shear ◽  
Resistance Spot ◽  
Ultra High Strength Steel ◽  
Ultra High Strength Steels ◽  
Cross Tension ◽  
Good Agreement

In this study, virtual and physical experimental investigations were performed on the resistance spot weldability of hot-formed ultra high strength steels (UHSS). The sheets were joined by the resistance spot welding as lap or cross joint. The mechanical properties were assessed in terms of cross tension strength (CTS) and tensile shear strength (TSS). The micro structural profile and weld nugget diameter were also investigated. Both virtual and physical methods yielding results are in good agreement. The results are discussed in the light of earlier work published in the literature and contribute to a better understanding on the evaluation of resistance spot weldability.

scholarly journals Preventing Nugget Shifting in Joining of Dissimilar Steels via Resistance Element Welding: A Numerical Simulation.

2021 ◽  
Author(s):  
Zhenghua Rao ◽  
Lei Liu ◽  
Yaqiong Wang ◽  
Liang Ou ◽  
Jiangwei Liu
Keyword(s):  
Spot Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Critical Issue ◽  
Resistivity Ratio ◽  
Dp Steel ◽  
Advanced High Strength Steels ◽  
High Electrical Resistivity ◽  
Resistance Element Welding ◽  
Welding Element

Abstract Joining the advanced high strength steels and the conventional steels is a critical issue for the manufacturing of lightweight vehicles. Resistance element welding (REW) is an emerging joining method for dissimilar metals and alloys by applying an auxiliary rivet-like resistance element in resistance spot welding (RSW). In this study, an electrical-thermal-mechanical coupled REW model for high-strength dual-phase (DP) steel and Q235 steel was developed by considering contact resistances as functions of temperature and surface contacting area. The results show that the welding element in REW serves to concentrate the current flow and thus Joule heat generation at the faying interface between the element and workpiece. For welding DP600 and Q235 workpieces with a small thickness ratio (≤0.4) or a high electrical resistivity ratio (≥3), REW could effectively mitigate nugget shifting between workpieces and reducing the thermal excursion to electrode as compared to RSW. Adding well-designed insulation layers in REW could further concentrate the current within the welding element, and enables a large-sized nugget at a lower current. This study is significant because it provides a better understanding to the electrical-thermal-mechanical behaviors with interfacial contacts in REW and contributes to its further advance.

scholarly journals Comprehensive Analysis of the Microstructure and Mechanical Properties of Friction-Stir-Welded Low-Carbon High-Strength Steels with Tensile Strengths Ranging from 590 MPa to 1.5 GPa

2021 ◽  
Vol 11 (12) ◽  
pp. 5728
Author(s):  
HyeonJeong You ◽  
Minjung Kang ◽  
Sung Yi ◽  
Soongkeun Hyun ◽  
Cheolhee Kim
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Joint Strength ◽  
Solid Phase ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Friction Stir ◽  
Welding Processes

High-strength steels are being increasingly employed in the automotive industry, requiring efficient welding processes. This study analyzed the materials and mechanical properties of high-strength automotive steels with strengths ranging from 590 MPa to 1500 MPa, subjected to friction stir welding (FSW), which is a solid-phase welding process. The high-strength steels were hardened by a high fraction of martensite, and the welds were composed of a recrystallized zone (RZ), a partially recrystallized zone (PRZ), a tempered zone (TZ), and an unaffected base metal (BM). The RZ exhibited a higher hardness than the BM and was fully martensitic when the BM strength was 980 MPa or higher. When the BM strength was 780 MPa or higher, the PRZ and TZ softened owing to tempered martensitic formation and were the fracture locations in the tensile test, whereas BM fracture occurred in the tensile test of the 590 MPa steel weld. The joint strength, determined by the hardness and width of the softened zone, increased and then saturated with an increase in the BM strength. From the results, we can conclude that the thermal history and size of the PRZ and TZ should be controlled to enhance the joint strength of automotive steels.

Sign in / Sign up

Export Citation Format

Share Document