INFLUENCE OF SECOND--PHASE PARTICLES CONTAINING Ti ON MICROSTRUCTURE AND PROPERTIES OF WELD--HEAT--AFFECTED--ZONE OF A MICROALLOY STEEL

et al. 2014

AMM

Using the oxide of high melting-point and high stability to pin the grain boundaries is an effective method to improve the welding performance of the HSLA steel in this study. A kind of HSLA steel is designed in this experiment. The thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding calcium into the steel in the form of Si-Ca alloy. The effect of calcium addition on the cast microstructure of HSLA steel was analysed. The results show that the cast microstructure is mainly consist of lamellar and acicular ferrite, a small amount of pearlite and bainite. Compared with the original steel, there are acicular ferrites presenting in the experimental steel after adding 5 wt% Ca, which are the microstructure that we hope to get. The acicular ferrite will have a positive impact on the mechanical properties of the subsequent rolled steel.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Calcium Addition on the Cast Microstructure of a Kind of HSLA Steel

et al. 2014

AMM

“…Smelting Equipment and Process. The directions of the microalloyed development in HSLA steel in every country throughout the world are as follows: (1) The obvious trend of carbon reduction presents. (2) The microalloy method combines with the thermo mechanical control process (TMCP).…”

Section: Methodsmentioning

confidence: 99%

“…When the steel plates use the high heat input welding, the strength and toughness of the welding heat affected zone (HAZ) decreases with the increase of the heat input welding [1]. Using the oxide of high melting-point and high stability to pin the grain boundaries is an effective method to improve the welding performance of the structure steel.…”

Section: Introductionmentioning

confidence: 99%

Effect of Calcium and Magnesium Addition on the Inclusions Distribution in the Cast Microstructure of HSLA Steel

et al. 2014

AMM

A new technology to obtain a fine-structured and high-toughness HAZ of HSLA steel for high heat input welding is developed using metallurgical thermodynamics, physical chemistry of metallurgy and material processing methods synthetically in this study. A kind of HSLA steel is designed in this experiment. The thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding calcium and magnesium into the steel in the form of Si-Ca alloy and Mg-Zr alloy, respectively. The effect of calcium and magnesium addition on the morphology and distribution of the inclusions in the cast microstructure of HSLA steel was analysed. The results show that the distribution of the inclusions is more dense and uniform with respect to the raw steel, and the size of the inclusions is smaller than the ones in the raw steel after adding Ca and Mg elements. Ca and Mg elements can accelerate the nucleation of the inclusions. The nucleation rate of the Mg element is relatively higher. The number of the inclusions in the adding Mg steel decrease more slowly relative to the adding Ca steel with the extension of the steelmaking time.

“…In some cases the yield-to-tensile ratio of steels with strength over than 600MPa is over than 0.95. It is very dangerous for application in some fields such as the Seismic structure and strain based engineering design。Moreover these steels have larger total elongation over than 18%, but the uniform elongation is only 3.0-4.0% [8][9]. Consequently a new challenge has been proposed that how to develop steels high strength, good toughness, low yield-to-tensile ratio and large uniform elongation.…”

Section: Introductionmentioning

confidence: 99%

The Tempering on Microstructure and the Yield-to-Tensile Ratio of High Performance Steels

Zhao

2012

AMR

The effects of tempering temperature on the microstructure and mechanical properties of 600MPa grade low carbon bainitic steel were investigated. The cause for the microstructure evolution has been investigated and the best tempering process was chosen to decrease the yield ratio of the steel. The influence of tempering process on the yield-to-tensile ratio of steels has been investigated by the aid of optical microscopy, SEM and XRD. The results show that after the TMCP processing the microstructure of steels mainly consist of lath martensite and bainite. The bainite and martensite have been refined markedly after the relaxation processing, therefore the properties of steels has been improved evidently. In order to decrease the yield-to-tensile ratio the steels underwent high temperature tempering. It has been found that during the tempering with the tempering temperature increased the yield-to-tensile ratio of steels decreased. The XRD and EBSD results show tempering temperature has considerable influence on the yield strength, but the influence on the tensile strength is not considerable. With the increase in tempering temperature, the low temperature toughness of steel can be improved considerably. The yield ratio of the steel was reduced after tempering at 650 °C and higher temperatures due to reversed austenitic phase transformation.