Investigations of Microstructure of Resistance Spot-Welded Joints Made of HSLA340 and DP600 Steels / Badanie Mikrostruktury Złączy Zgrzewanych Punktowo Ze Stali HSLA340 I DP600

2012 ◽  
Vol 57 (4) ◽  
pp. 1081-1086 ◽  
Author(s):  
A. Ignasiak ◽  
M. Korzeniowski ◽  
A. Ambroziak
Keyword(s):  
Welded Joints ◽  
High Strength Steel ◽  
Hsla Steel ◽  
High Strength ◽  
Dual Phase ◽  
Low Carbon ◽  
Spot Welds ◽  
Bainite Microstructure ◽  
Martensite Microstructure ◽  
Carbon Martensite

The paper presents results of metallographic investigations of spot welds made of high-strength steel HSLA340 and dual-phase DP600 steel. Low-carbon martensite microstructure was found in the weld nugget of HSLA steel. The DP600 steel shows martensite and bainite microstructure. For both steels, no carbides of microadditives were found because they dissolved in liquid nugget and could not precipitate again because of rapid heat abstraction. Moreover, no transcrystallisation was found in both steels, which proves good mixing of the materials within the weld.

Effect of Tempering Process on Residual Stress in Hot Rolled Low Carbon Martensite High-Strength Steel Strip

2013 ◽  
Vol 690-693 ◽  
pp. 222-226 ◽  
Author(s):  
Lin Sun ◽  
Zhi Yi Zhao ◽  
Xiao Zhen Yang ◽  
Run Dong Xue
Keyword(s):  
Residual Stress ◽  
Thermal Stress ◽  
Stress Distribution ◽  
High Strength Steel ◽  
Steel Strip ◽  
High Strength ◽  
Low Carbon ◽  
Width Direction ◽  
Hot Rolled ◽  
Carbon Martensite

Distribution of residual stress in hot rolled low carbon martensite high-strength steel strip was measured by means of blind-hole method in the steel before and after tempering. The hot rolled low carbon martensite high-strength steel strip was tempered at 450°C, 500°C, 550°C or 600°C. Before tempering, the value of the residual stress along the width direction is maximum at the edge, intermediate at the center, minimum at the 1/4 of the strip. The figure of the residual stress distribution along the width direction is like the shape of the letter M. Residual stress of the strip is reduced after tempering. When tempering at 450°C or 500°C, evolution of residual stress is caused by changes of thermal stress. Distribution of residual stress becomes gentle. With tempering temperature increasing, distribution of residual stress is reversed, because evolution of thermal stress and phase transition stress changes in different time.

Development and Production of Ultra-High Strength Linepipes With Dual-Phase Microstructure for High Strain Application

2007 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Mitsuru Okatsu ◽  
Junji Shimamura ◽  
Shigeru Endo ◽  
Nobuo Shikanai ◽  
...  
Keyword(s):  
Base Material ◽  
High Strength ◽  
Controlled Rolling ◽  
Accelerated Cooling ◽  
Heating Process ◽  
Dual Phase ◽  
Low Carbon ◽  
Cooling Process ◽  
Bainite Microstructure ◽  
Microstructural Control

Extensive studies to develop high strength linepipes with higher deformability have been conducted. One of the key technologies for improving deformability is dual-phase microstructural control. Steel plate with ferrite-bainite microstructure can be obtained by applying Thermo-mechanical controlled processing, TMCP, made up with controlled rolling and accelerated cooling process. Low carbon-boron free steels were used to enable the ferrite formation during cooling after controlled rolling, and the accelerated cooling process with ultimate cooling rate enabled to achieve high strength of up to X120 grade. On-line heating process by induction device was also applied subsequently after accelerated cooling in order to improve Charpy energy of the base material and homogeneity of material properties in the plate. Trial production of X120 high deformability linepipe was also conducted by applying dual-phase microstructural control. Microstructural and mechanical properties of X120 linepipe are introduced in this paper.

Martensitic Transformation in a Low-Alloy Ultra-High-Strength Steel

2011 ◽  
Vol 295-297 ◽  
pp. 1470-1473 ◽  
Author(s):  
Zhi Xia Qiao ◽  
Dan Tian Zhang ◽  
Yong Chang Liu ◽  
Ze Sheng Yan
Keyword(s):  
Martensitic Transformation ◽  
High Strength Steel ◽  
Lath Martensite ◽  
High Strength ◽  
Transformation Rate ◽  
Low Carbon ◽  
High Carbon ◽  
Process Characteristics ◽  
Ultra High Strength Steel ◽  
Carbon Martensite

Martensitic transformation is the most important phase transformation strengthening the 30CrNi3MoV ultra-high-strength steel during heat treatment process. Characteristics of the martensitic transformation in the 30CrNi3MoV steel were investigated by means of dilatometric measurements and microstructural observations. The results showed that the starting and finishing martensitic transformation temperatures of the 30CrNi3MoV explored steel are 317°C and 167°C respectively, which are hardly influenced by the cooling rate from austenite region. Such a wide temperature range of martensitic transformation in the 30CrNi3MoV steel results into the diversity of martensite microstructures. The microstructures in all the quenched 30CrNi3MoV samples are composed of mixture of lath and acicular martensite, corresponding to low-carbon and high-carbon martensite respectively. The transformation rate of acicular martensite is much slower than that of lath martensite, which can be attributed to the stabilization of the rest high-carbon austenite after the formation of lath martensite.

MITTAL DI-FORM T700, HF80Y100T

Alloy Digest ◽  
2007 ◽  
Vol 56 (2) ◽  
Keyword(s):  
Automotive Industry ◽  
High Strength ◽  
Martensite Phase ◽  
Carbon Steels ◽  
Ferrite Phase ◽  
Dual Phase ◽  
Low Carbon ◽  
Advanced High Strength Steel ◽  
Dp Steels ◽  
Soft Ferrite

Abstract MITTAL DI-FORM T700 and HF80Y100T are low-carbon steels with a manganese and silicon composition. Dual-phase (DP) steels are one of the important advanced high-strength steel (AHSS) products developed for the automotive industry. Their microstructure typically consists of a soft ferrite phase with dispersed islands of a hard martensite phase. The martensite phase is substantially stronger than the ferrite phase. The DI-FORM grades exhibit low yield-to-tensile strengths, and the numeric designation in the name corresponds to the tensile strength. This datasheet provides information on microstructure and tensile properties as well as deformation and fatigue. It also includes information on forming. Filing Code: SA-561. Producer or source: Mittal Steel USA Flat Products.

MITTAL DI-FORM T590, T600

Alloy Digest ◽  
2007 ◽  
Vol 56 (1) ◽  
Keyword(s):  
Tensile Strength ◽  
Automotive Industry ◽  
High Strength ◽  
Martensite Phase ◽  
Ferrite Phase ◽  
Dual Phase ◽  
Bend Strength ◽  
Low Carbon ◽  
Advanced High Strength Steel ◽  
Soft Ferrite

Abstract MITTAL DI-FORM T590 and T600 are low-carbon dual-phase steels containing manganese and silicon. Dual-phase (DP) steels are important advanced high-strength steel (AHSS) products developed for the automotive industry. Their microstructure typically consists of a soft ferrite phase with dispersed islands of a hard martensite phase. The martensite phase is substantially stronger than the ferrite phase. The DI-FORM grades exhibit low yield-to-tensile strength ratios. The numeric designation in the grade name corresponds to the tensile strength in MPa. This datasheet provides information on microstructure, tensile properties, and bend strength as well as fatigue. It also includes information on forming. Filing Code: SA-558. Producer or source: Mittal Steel USA Flat Products.

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