Influence of reflow processing conditions on the uniformity of the chromium passivation film on tinplate

This study aims to systematically analyze the key parameters of the reflow process that influence the uniformity of the chromium passivation film coated on tinplate. The distribution characteristics of the chromium passivation film coated on the tinplate surface under different treatment conditions were systematically characterized using the scanning Kelvin probe technique, X-ray photoelectron spectroscopy, and X-ray diffraction. Results indicate that the use of flux reduces the porosity of tin coating, thereby favoring the uniform growth of the passivation film. Furthermore, an increase in the reflow power and quenching temperature facilitates the homogeneous distribution of the passivation film on the tinplate surface,particularly when treated with electrolytic cathodic sodium dichromate.

An overview of strain ageing in low carbon steels

Strain ageing in steel was first observed during the 19th century when the maximum load carrying capacity of a test piece was increased after it had been retested following a previous series of testing in a plastic range. Over the last decades, a great deal of research has been performed to gain deeper insights into the phenomenon of strain ageing. The synergistic development of theoretical hypothesis and new experimental evidences has promoted the understanding of the mechanisms underlying strain ageing. The content of this paper is organized into four components. First, we have compared the main theories developed in recent years. Second, we have summarized the metallurgical effects on the strain ageing behavior observed in experiments. Moreover, we have made an attempt to correlate the experimental results and the above-mentioned theories. Third, we have proposed a feasible solution to control strain ageing in low carbon steels. Finally, we have elaborated the potentiality of the atom probe technique in facilitating direct characterization of the distribution of solute atoms.

Effect of heating rate on the recrystallization microstructure and property of ultra-low-carbon steel

In the present work,the microstructure,texture,and mechanical properties of a cold-rolled Ti-IF steel,after annealing at different heating rates,have been investigated.The results reveal that the mean grain size is gradually refined from 19.2 to 16.3 μ m as the heating rate increases from 4 to 50 ℃/s,but refined only slightly at heating rates of over 50 ℃/s.The recrystallization microstructure has a strong texture,which is a result of the sharpening of the favorable { 111 }//ND （normal direction） texture components or γ-fiber.With increasing heating rates,the peak value off（g） of γ-fiber decreases from 17 to 9.The yield and tensile strengths increase gradually as the heating rate increases from 4 to 50 ℃/s,but remain almost unchanged at heating rates of more than 50 ℃/s.The total elongation and uniform elongation increase gradually as the heating rate increases from 4 to 100 ℃/s,but decreases slowly for heating rates higher than 100 ℃/s.As the heating rate increases from 4 to 100 ℃/s,the plastic strain ratio of the steel decreases from 2.8 to 2.2; however,it increases to 2.9 for heating rates above 100 ℃/s.The strain hardening exponent remains unchanged at 0.27 in all annealing cycles.

Effect of Pb content on the surface topography and corrosion resistance of hot dip Zn-Al-Mg coatings

In this study,the effect of Pb content on the surface morphology and salt spray corrosion resistance of hot dip Zn-AI-Mg coatings was investigated. The results showed that the coating surface easily formed small grains of zinc spangle structures and that the salt spray con＇osion resistance of the coating decreased when Pb content was greater than 0.01%. The microstructure and energy dispersive spectrum analysis of surface and cross-sectional areas was performed by scanning electron microscopy. Pb content present in the coating was analyzed by glow discharge spectrum. The results showed that the distribution of Pb in the coating was not uniform. The Pb content was segregated on the surface and at the cross-section of the Zn-A1-MgZn2 ternary eutectic structure,especially,on the surface of the Zn-A1-MgZn2 ternary eutectic structure.

Research on dent resistance of lightweight three-piece cans

An experimental apparatus and a numerical simulation model were built for investigating the dent resistance of lightweight three-piece cans.The dent resistance of raw materials 0.19 mm T4 and 0.17 mm DR7M was compared.It was found that when the thickness reduced from 0.19 to 0.17 mm,the dent resistance became about 80％ of that before thinning.This provides a guidance for the continuous thinning of three-piece cans.

Preface

25 years ago, Baosteel＇ s 1 st cold rolling mill was put into production. Since then, Baosteel has been exploring its own way to promote technology progress. In the beginning, the company imported the core technology from abroad, and after years of assimilation and absorption, it gradually achieved independent innovation. So far, Baosteel has always been leading the developing trend of the cold rolling technology, and its products represent the highest level in China, and are also one of the best in the world.