Production of corrosion-resistant 09ГСФ steel

New production technology for low-alloy 09ГСФ steel for rolled sheet resistant to hydrogen-sulfide corrosion is described. The quantity of modifier introduced determines the impurity content of the metal after deep refining to remove sulfur and nonmetallic inclusions, the types of inclusions formed, and hence the resistance of the metal to corrosion cracking. Row inclusions formed in the sheet after nonoptimal ladle treatment of the steel are mainly responsible for the impairment of corrosion resistance.     

Spheroidization process in large-deformed high-carbon steel

In this study,the spheroidization process of large-deformed steel under various conditions was researched. Steel with a high carbon content(1.0% C)was first treated thermomechanically using multipass rolling.Then it underwent spheroidization treatments at different heating temperatures,using various heating times and cooling rates.Spheroidization processes with a lower heating temperature,shorter heating time,or faster cooling rate than those of the traditional process all showed good results,indicating that the spheroidization process was promoted significantly by the large deformation process.Grain refinement and fragmentation of cementite,along with the large deformation process,promoted this spheroidization process.     

Sustainability–steel and the environment

Abstract

A two-dimensional heat and fluid flow model was used to simulate the plasma arc furnace, where the flow is governed by the steady state incompressible Navier–Stokes equations. The flow has been taken as turbulent and the standard k-epsilon model was used to simulate the turbulence in the flow. The coupled non-linear differential equations were solved with suitable boundary conditions and temperature dependent plasma properties at atmospheric pressure by employing an efficient finite volume method. The calculations and heat transfer to various parts of the furnace were calculated for argon, nitrogen and hydrogen plasmas. The voltage–current characteristic for the different types of plasma and the effect of other process parameters on heat transfer are discussed.     

Short-term creep of Cт3 steel

The behavior of Cт3 structural steel in brief heating (no more than 2 h) at 450–650°C is investigated, when the initial stress is below the yield point. In these conditions, the initial ferrite–pearlite structure of the steel is relatively stable, and no recrystallization is observed. At a test temperature of 450°C, when the stress is ~0.8 of its yield point at 20°C, Cт3 steel may fail within a matter of hours or days. At 650°C, when the stress is σ/σ _0.2 ²⁰ > 0.8 of the yield point at 20°C, failure sets in within minutes. The calculated activation energy of creep for steel is 310.8–387.8 kJ/mol, which is comparable with the activation energy for Cт3 the self-diffusion of α iron.     

The comprehensive utilization of Baosteel steel slag

Summarizes the processes and development of Baosteel slag processing techniques such as the instantaneous slag chill （ISC） process, the tank-type hot disintegrating process and the rotary drum process. A detailed introduction of the slag comprehensive utilization at Baosteel is given. The details of Baosteel＇ s comprehensive utilization in the fields of simering materials, returned slag for steelmaking, road construction, cement production, mixed concrete, new construction materials, ground-filling materials and reinforced material for soft earth are given. Emphasis is placed on source management and ensuring that from both organizational and managerial perspectives, Baosteel＇ s slag processing techniques are safe and energy-saving, thus constantly demonstrating the issue of sustainable development.     

Surface rust of cold-rolled bell-type annealing strip steel

This paper offers systematic analysis and in-depth research on the surface rust problem of cold-rolled bell-type annealing strip products.The defect characteristics,occurrence rules,generation mechanism,and influencing factors of surface rust are presented.This research employed a cold-rolled bell-type furnace annealing unit in a coastal steel factory as an example and conducted production process tests,on-site production tests,scanning electron microscopy,energy spectrum analysis,MINITAB statistical analysis,etc.Moreover,six significant influencing factors and their rules were studied:the cooling time of the final cooling table,the storage time of the intermediate storage,the temperature setting of the intermediate storage,the temperature of leveling liquid,the purging pressure of leveling machine,and the dust in the environment.     

Liquid steel transfer—the delivery of quality

During recent years, in parallel with developments in high-speed casting, there have been increasing demands for improved steel quality. These demands are being met by advances in our knowledge of the chemical, physical and thermal interactions between steel, gas, slag and refractory phases which take place within individual reactors as well as during transfer operations. Transfer operations must be precisely controlled, otherwise they become destroyers of quality, and quality achieved within one reactor can be lost during transfer to the next.     

Phase transformation of TRIP-aided multiphase steel during continuous cooling

The phase transformation characteristics of a high-strength TRIP-aided multiphase cold-rolled steel during continuous heating at different cooling rates were studied by means of dilatometry,and the critical temperatures were also determined.The samples were fully austenitized at 1 050 ℃ and then cooled at different cooling rates ranging from0.5 ℃/s to 100 ℃/s.The continuous cooling transformation(CCT)curves were obtained for the experimental steel.The experimental results showed that a high cooling rate depressed the formation of ferrite and pearlite and promoted the formation of bainite and martensite,leading to a higher hardness.A large amount of martensite in high-strength TRIP-aided multiphase cold-rolled steel can be obtained at cooling rates in excess of 50 ℃/s.The experimental results provide guidelines for cooling control and heat treatment in real steel production.     

韩国INI steel公司轨梁轧钢厂考察见闻

本文主要介绍了韩国INI steel公司轨梁轧钢厂生产工艺、设备、技改等情况,旨在为钢轨生产线改造提供借鉴.     

Ductile-to-Brittle transition in 〈111〉 hadfield steel single crystals

The deformation mechanism and the character of fracture of 〈111〉 austenitic Hadfield steel single crystals are studied during tension in the temperature range 77–673 K by scanning and transmission electron microscopy. It is found that a change in the fracture mechanism from ductile to brittle fracture according to the fractography criterion takes place at a higher temperature than that determined from a change in the elongation to failure of the single crystals. The ductile-to-brittle transition in the Hadfield steel single crystals is shown to be related to a high level of deforming stresses induced by solid-solution hardening and to mechanical twinning.     

Microstructure–mechanical property relationship in hot-rolled high-Al-low-Si dual-phase steel

In this study, the effect of finish rolling temperature and coiling temperature on the microstructure and mechanical properties of high-Al-low-Si dual-phase (DP) steels is explored. Two different finish rolling temperatures (850 and 790°C) and three different coiling temperatures (200, 250 and 300°C) were studied. The results indicated that all the different processing conditions led to ferrite-martensite DP microstructure. With the decrease in finish rolling temperature, the volume fraction of ferrite was increased and martensite content was decreased. When the coiling temperature was increased to 300°C, autotempered martensite was obtained, which led to the softening of martensite and decrease in tensile strength and strain hardening ability, but higher post-necking elongation. Moreover, the nanoscale Nb-based carbides played a crucial role in refining the microstructure of hot-rolled high-Al-low-Si DP steel. EBSD (Electron Backscattered Diffraction) analysis revealed that the ferrite grains were fine, and decrease in finish rolling temperature and coiling temperature led to an increase in low-angle boundaries. When the finish rolling temperature was decreased to 790°C and coiling temperature was decreased to 200°C, the steel had excellent mechanical properties with tensile strength of 885?MPa, uniform and total elongation of 16.0 and 25.94%, respectively, and the product of tensile strength and total elongation was 20?264?MPa%. The improvement of strength and plasticity can be attributed to the fraction of ferrite and martensite, precipitation of NbC, fine microstructure.     

Stress-induced transformation in a carburized steel—Experiments and analysis

Stress-induced transformation of austenite to martensite was studied experimentally and numerically to gain an understanding of the increase in transformation strain with increasing tensile both and decreasing temperature. In addition, the anisotropy of the transformation strains was determined both experimentally and numerically. The material chosen for the study was a carburized 4320 steel with 35% retained austenite content. Monotonic and cyclic experiments were conducted in the range from -60 to 150°C. At 22°C, the volumetric transformation strain reached 0.006 at fracture in the uniaxial tensile test and 0.004 in the torsion test. Numerical calculations of the volumetric transformation strain and the anisotropy of the transformation strains were obtained with a modified Eshelby model where planes favorably oriented gradually transformed as stress was applied. The analysis predicted the experimentally observed transformation strains under both uniaxial and torsional loadings. The model also predicted the anisotropy of the transformation strains that was observed in experiments.     

Study of the spangle size of 55％ Al-Zn-Si steel

The spangle size of the 55% Al-Zn-Si steel is affected by the composition of the zinc pot,the cooling capacity after plating,and the substrate. According to previous studies,the size of spangles can be reduced by increasing the cooling ability after plating,and by adding Ti in the zinc pot. However,these two methods cannot reduce the spangle size smaller than 1. 5 mm. Therefore,in this study,we have focused on the influence of substrates on the formation of spangles of 55% Al-Zn-Si steel by comparing and analyzing substrates with different surface roughness,composition,morphology,crystal orientation,and alloy layers.     

Early-stage widmanstatten growth of the γ phase in a duplex steel

The present work studies the Widmanstatten γ-phase morphology and crystallographic orientation relationships with ferrite during its initial-stage growth in a duplex steel. Transmission electron microscopy (TEM) and convergent-beam electron diffraction (CBED) analyses have been applied to determine the orientation relationships with high precision. When the secondary γ phase and the α phase have special orientation relationships close to the K-S (Kurdjumov-Sachs) relation, the preferential growth involves γ phase, protruding into α phase and this leads, finally, to the formation of Widmanstatten needles. The needles grow nearly along the invariant-line direction, but they do not satisfy exactly the K-S relation, and a slight angular deviation (ϑ _[110]α ) is always present. This deviation is explained by a compromise between the well-known invariant-line condition, which offers the easiest way for directional growth of the γ phase, and a good atomic matching of the close-packed (111) _γ and (110) _α planes of both phases. A matching minimum at ϑ _[110]α = 2.3 deg is obtained when only three pairs of the nearest-neighbor atoms are considered in an atomic misfit calculation.     

Water consumption and wastewater discharge in China’s steel industry

China’s steel industry is one of the major water consuming and wastewater discharge-producing industries. Based on a water flow model, this study provides reasonable and clear definitions of water usage indexes for steel production. Using a survey of key producers, the status and problems of water consumption and wastewater discharge in Chinese steel industry are analyzed. The developments of water conservation and emission reduction are divided into three different stages, and present a slide decreasing curve. At the process level, coking is the heaviest pollution unit, while ironmaking and steelmaking are key parts of water consumption. Although the water resource efficiency has been significantly improved, the water usage level of key producers in China has exceeded the average world steel level; however, it is still lower than other advanced countries. Therefore, some measures and recommendations need to be implemented for Chinese steel industry to save water and reduce emissions.     

Study on the heat resistance of 55％ Al-Zn steel plates

Post-treated 55% Al-Zn steel plates,which have adequate mechanical properties and corrosion resistance,are widely used for automobiles,household appliances,and other products. The heat resistance of 55% Al-Zn steel plates is slightly lower than that of aluminum plates or hot-dip aluminized steel plates,but their corrosion resistance is better. Herein,by testing at different baking temperatures and for different periods,the trends of color,gloss,and loss weight have been analyzed. The heat-resistant properties of differently post-treated 55% Al-Zn steel plates,aluminum plates,and hot-dip aluminized steel plates have been studied.     

Equilibrium kinetics of manganese-ore carbon-reduction between molten steel and slag

The equilibrium condition between molten steel and slag during manganese-ore carbon-reduction was studied using both resistance furnaces and induction furnaces. The resistance furnace experiment shows that it is difficult to further increase the yield of manganese (maintained at around 37%) without stirring. The bottom blowing and top slag stirring were strengthened in the induction furnace test, where white slag was continuously produced to promote the carbon reduction of manganese dioxide in slag between molten steel and slag. Under these conditions, the yield of manganese between molten steel and slag can reach greater than 90%. The main factors affecting the manganate capacity are the carbon and silicon content in molten steel. The limiting process of manganese mass transfer is mainly the mass transfer of manganese in molten steel. Under carbon reduction in molten steel the limiting factor affecting the mass transfer of manganese is the mass transfer of manganese in slag.