ultra high strength steel
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2022 ◽  
Vol 81 ◽  
pp. 103120
Author(s):  
Jacek Tomków ◽  
Michał Landowski ◽  
Dariusz Fydrych ◽  
Grzegorz Rogalski

Author(s):  
Kornél Májlinger ◽  
Levente T. Katula ◽  
Balázs Varbai

The tensile strength of newly developed ultra-high strength steel grades is now above 1800 MPa, and even new steel grades are currently in development. One typical welding process to join thin steels sheets is resistance spot welding (RSW). Some standardized and not standardized formulas predict the minimal shear tension strength (STS) of RSWed joints, but those formulas are less and less accurate with the higher base materials strength. Therefore, in our current research, we investigated a significant amount of STS data of the professional literature and our own experiments and recommended a new formula to predict the STS of RSWed high strength steel joints. The proposed correlation gives a better prediction than the other formulas, not only in the ultra-high strength steel range but also in the lower steel strength domain.


Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7609
Author(s):  
Georg Baumann ◽  
Dominik Niederkofler ◽  
Christian Ellersdorfer ◽  
Florian Feist

Split Hopkinson bars are used for the dynamic mechanical characterisation of materials under high strain rates. Many of these test benches are designed in such a way that they can either be used for compressive or tensile loading. The goal of the present work is to develop a release mechanism for an elastically pre-stressed Split Hopkinson bar that can be universally used for tensile or compressive loading. The paper describes the design and dimensioning of the release mechanism, including the brittle failing wear parts from ultra-high strength steel. Additionally, a numerical study on the effect of the time-to-full-release on the pulse-shape and pulse-rising time was conducted. The results of the analytical dimensioning approaches for the release mechanism, including the wear parts, were validated against experimental tests. It can be demonstrated that the designed release concept leads to sufficiently short and reproducible pulse rising times of roughly 0.11 ms to 0.21 ms, depending on the pre-loading level for both the tension and compression wave. According to literature, the usual pulse rising times can range from 0.01 ms to 0.35 ms, which leads to the conclusion that a good average pulse rising time was achieved with the present release system.


Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1977
Author(s):  
Tomoyoshi Maeno ◽  
Ken-ichiro Mori ◽  
Hiroki Homma ◽  
Ali Talebi-Anaraki ◽  
Ryohei Ikeda

Hot-stamped products are widely used for the body-in-white of an automobile as they are lightweight and improve crashworthiness. A hot-stamping process using planar compression was developed to strengthen corners of ultra-high strength parts by local thickening and hardening. In this process, the corners are thickened by compressing the blank in the planar direction with the upper and lower dies while blocking the movement of both edges with stoppers in the latter stage of forming. Thickening of the corners largely heightens the strength of the formed parts. Not only the thickness but also the hardness of the corner was increased by large plastic deformation and die quenching. For a hot hat-shaped part, a 30% increase in thickness and a 530 HV20 hardness around the corners were attained. The bending rigidity and strength of the formed parts thickened by 30% in the corners increased by 25% and 20%, respectively. In addition, the improvements of the part shape accuracy and the sidewall quenchability were obtained.


2021 ◽  
Vol 904 ◽  
pp. 154-158
Author(s):  
Zhi Ling Wang

The welding of WELDOX960 ultra-high strength steel must consider not only the strength but also the toughness of the welding zone. In this paper, a new welding process with low strength matching backing layer is studied, that is, we choose ER50-6 wire for backing welding, use T union gm120 wire for MAG welding filling, and complete the cover welding. We prepared two groups of welding samples of ER50-6 wire backing welding and T union gm120 wire backing welding. Then we test the samples by optical metallography, tensile test, impact test and hardness test. The results show that the properties of the two kinds of backing weld can meet the requirements. The basic structure of the weld outside the backing layer of the two welding methods is similar, which are acicular ferrite and carbide. Using ER50-6 welding wire as backing, the microstructure of the weld is uniform and fine ferrite grain and a small amount of pearlite. Using T union GM120 high strength steel as backing, the microstructure of the weld is acicular ferrite and carbide. The toughness of ER50-6 is higher than that of T union GM120, and the hardness is lower than that of T union GM120.The research results have been successfully applied to the welding of large tonnage truck crane boom, and the enterprise has achieved high economic benefits.


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