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Yu Y.,Shougang Institute of Technology | Meng X.-T.,Shougang Institute of Technology | Wang L.,Shougang Institute of Technology | Wang C.,Shougang Institute of Technology | And 2 more authors.
Kang T'ieh/Iron and Steel | Year: 2014

The stamping cracking defect is the main problem for the utility of high strength beam steel with the strength exceeding 700 MPa. Controlling the inclusions and center segregation and grinding the shear plane can reduce the probability of stamping cracking. The paper was mainly focused on hot rolling process to investigate the cause and mechanism leading to stamping cracking. The microstructure, mechanical properties, heating and rough rolling temperature system, finishing rolling and coiling temperature system, finishing rolling speed, as well as the influence of hot charging system, were all comparatively analyzed, considering the difference between the normal strip and stamping cracking strip of 750 MPa level beam steel. And some beneficial experiences were provided for production of this kind of steel. The results show that ensuring fine rolling speed is the important way to low the probability of stamping cracking defect.


Wang C.,Shougang Institute of Technology | Yu Y.,Shougang Institute of Technology | Pan H.,Shougang Institute of Technology | Wang L.,Shougang Institute of Technology | And 2 more authors.
Kang T'ieh/Iron and Steel | Year: 2014

Aiming at eliminating the banded red scale defect existing on the strip surface of high strength steel for mechanical engineering application, the microstructure of the cross section and surface at local defect position was observed through SEM and EPMA, and the uniformly-spaced characteristics related to the descaling system of hot rolling production line was studied. The results show that the scale thickness at the banded position is thicker than that of any other parts of the strip and there is a Si enrichment region between scale and strip. The correspondence of the spacing of banded scale and the spacing of the spray nozzles reveals that the existence of the banded scale defect is strongly related to the weak effectiveness of the finishing descaling process. The oxidization property of the given steel was analyzed through differential thermal analysis. The rapid growth of the scale thickness was found before the finishing descaling process in practice, and scale existing as Fe2SiO4 phase with strong adhesion ability leads to the difficulties of descaling process. Based on the study of the red scale formation mechanism, the control keys of hot rolling process and steelmaking have been proposed, which successfully removed the banded red scale defect.


Wang Q.,University of Science and Technology Beijing | Li S.,Shougang Qianan Steel Company | Li Y.,SINOSTEEL MECC | Zhang L.,University of Science and Technology Beijing | Wang X.,University of Science and Technology Beijing
TMS Annual Meeting | Year: 2013

Numerical simulation on the fluid flow in a Flow-Control Mold (FC-Mold) were performed. The motion of inclusions were calculated. With FC-Mold, the flow pattern and surface velocity become more symmetrical, and at higher casting speed the velocity of liquid steel in the top region of the mold was largely reduced with the highest velocity of the meniscus reducing from 0.65 m/s to 0.4 m/s, and the meniscus shape became flatter. With FC-Mold, more inclusions approached to the surface of the slab and the amount of inclusion in the center of mold became fewer. Larger inclusions were easier to remove, however, the EM filed of the FC-Mold could hardly improve the removal of inclusions from the molten steel.


Yang W.,University of Science and Technology Beijing | Li S.,University of Science and Technology Beijing | Li S.,Shougang Qianan Steel Company | Li Y.,SINOSTEEL MECC | And 4 more authors.
TMS Annual Meeting | Year: 2013

Ultra-low carbon steel, in which titanium is used to fix the interstitial atoms such as C and N, is well used for automobile. During the RH refining process, the evolution of oxide inclusions was analyzed using ASPEX and acid extraction. It was found that after Ti addition a large amount of Al-Ti-O inclusions generated, and the Ti content in the oxides decreased as the refining time increased. It was estimated that most of the oxides could be removed before the time of 10 min after Ti addition. The average size of alumina increased while that of Al-Ti-O inclusions decreased during the refining process. After Ti addition, the Al2O3 clusters transformed to coral shape and there existed three types of Al-Ti-O inclusions. Accordingly, a formation mechanism of Al-Ti-O inclusion was proposed.


Wang C.,Shougang Institute of Technology | Yu Y.,Shougang Institute of Technology | Wang L.,Shougang Institute of Technology | Chen J.,Shougang Qianan Steel Company | Xu H.-W.,Shougang Institute of Technology
Kang T'ieh/Iron and Steel | Year: 2014

Based on the morphology observation of fracture and precipitate of high strength IF steel containing phosphorus with SEM and TEM, the segregation of coarse dendritic Fe(Nb, Ti)P at the grain boundaries was concluded as the mainly reason inducing the strip fracture during straightening process. Through the precipitate dissolving experiments upon the fracture strip and the thermal simulation experiments simulating different laminar cooling speed, the precipitation temperature range and factors causing Fe(Nb, Ti)P segregation at the grain boundaries was revealed. On the basis of the theoretical research, several effective methods are proposed to reduce the occurrence of strip fracture including the optimization of rolling temperature, cooling speed of laminar cooling, composition design, and coiling temperature etc, which has succeeded in restraining the strip fracture during straightening process.

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