Influence of hot rolling on the microstructure of lean duplex stainless steel 2101

In this work, the microstructure and the strain partitioning of lean duplex stainless steel 2101 (LDX 2101) during different hot-rolling processes are investigated by optical microscopy and electron-backscattered diffraction (EBSD). The results show that the LDX 2101 exhibits poor thermoplasticity at high temperature. The four-pass hot-rolled plates show fewer edge-cracking defects and superior thermoplasticity compared with the two-pass hot-rolled plates prepared at different temperature. The phase boundary is the weakest site in the LDX 2101. The cracks are initiated and propagated along the phase boundaries during the hot-rolling process. According to the EBSD analysis, the increase of the hot-rolling pass can dramatically improve the strain distribution in ferrite and austenite phases and promote the strain transmission in the constituent phases, thereby improving the coordinated deformation ability of the two phases. This effect further in- creases the thermoplasticity and reduces the formation of edge cracks in LDX 2101.

Wave Processes and Mass Transfer on the Copper-Stainless Steel Interface under Solid Phase Bonding by High-Temperature Rolling

The paper presents the study of hierarchy of deformation wave-processes from nano- to macro-structural level, which takes place in dissimilar materials, bonded by high-temperature vacuum rolling in solid phase. The focus was on the processes that occur on the interface of the bonded materials: mass trasfer of impurities and alloying elements stimulated by deformation, the study of nano- and micro-hardness.

EPS钢板切换热轧带钢生产应用技术研究

为了解决目前梁类零部件生产所用热轧带钢存在的氧化皮掉落造成设备停机、污染环境等问题,以EPS钢板的转产切换为主要研究对象,采用试验验证以及现地现物解决问题的方式,分析了热轧带钢氧化皮在辊压过程中掉落的原因,分析了绿色清洁表面处理技术(EPS)钢板表面质量高、零件成形后不需要抛丸的技术优势,提出了EPS材料的技术要求:钢板屈服强度为530~560MPa,抗拉强度为600~630MPa,断后伸长率≥22%,同时需要满足冷弯性能要求;经过EPS处理后的表面平均粗糙度Ra≤5.0μm。最终促成了EPS钢板转产切换。

Mathematical model for cooling process and its self-learning applied in hot rolling mill

Control precision of coiling temperature is one of the key factors affecting the profile shape and surface quality during the cooling process of hot rolled steel strip.For this reason,the core of temperature control precision is to establish an effective cooling mathematical model with self-learning function.Starting from this point,a cooling mathematical model with nonlinear structural characteristics is established in this paper for the cooling process of hot rolled steel strip.By the analysis of self-learning ability,key parameters of the mathematical model could be constantly corrected so as to improve temperature control precision and adaptive capability of the model.The site actual application results proved the stable performance and high control precision of the proposed mathematical model,which would lay a solid foundation to improve the steel product qualities.

Application of Microstructure Engineering in Steel Coil Cooling Process

The coil cooling and its role in a hot strip mill were reviewed. A mathematical model was developed to describe and analyze the thermal history and its impact on precipitation phenomena during coil cooling for plain carbon, HSLA-V and HSLA-Nb steels. The predicted result of the thermal model was compared with that measured from industrial coil. The effect of cooling condition and coil dimension on the thermal history and final mechanical properties of the steel strip was examined. The coiling temperature and cooling rate have crucial influence on the precipitation strengthening.

EPS材料耐腐蚀性的研究

通过对EPS材料的化学成分进行检测,初步了解材料的基本特性。对EPS材料表面防护层的耐湿热性、耐腐蚀性进行了研究。结合研究结果,在目前国内钢厂EPS处理技术情况下,提出了EPS材料在卡车底盘制造领域中可应用的范畴和注意事项。

310S不锈钢热卷表面氧化铁皮磁性研究及EPS表面处理工艺实践

通过实验室电加热炉,获得了310S不锈钢热轧板表面氧化铁皮。对获得的氧化铁皮进行了磁性吸附实验、物相分析、扫描电镜形貌分析。实验结果表明:奥氏体不锈钢310S不锈钢热轧板氧化铁皮是完全具有磁性的尖晶石结构,可以通过EPS处理去除大部分的氧化皮。310S钢卷通过EPS处理后,热卷的酸洗效率能提高一倍。

新型车架大梁钢涂装工艺研究——绿色免酸洗EPS表面处理钢初探

通过对热轧钢板和绿色免酸洗表面处理钢(简称EPS钢)的工艺、耐腐蚀性研究,分析了EPS钢具备除锈等级高,除锈后钢材表面质量好的优点,提出了EPS钢可用于车架大梁钢等零部件,值得推广和应用。

Effect of Alloying Element on Process Control of High Strength Hot-Rolled Dual Phase Steel

Microstructure evolution of C-Si-Mn-Nb,C-Si-Mn-Cr-Nb and C-Si-Mn-Cr-Mo-Nb tested steels during step-cooling process were studied.Effects of alloying element and process data on microstructure and mechanical properties of high strength Nb bearing DP steel were analyzed,to illustrate the relationship between alloy composition design and process control stability during DP microstructure and property control.It is shown that,700MPa ferrite and martensite DP steel is obtained respectively by three kinds of composition tested steel under different step-cooling process.C-Si-Mn-Nb steel with simple alloying design of low cost is provided with low hardenability,and has strong process sensibility during microstructure evolution.DP microstructure of ferrite and martensite of C-Si-Mn-Nb steel just can be obtained by coiling at low temperature of 250℃.The process control stability of C-Si-Mn-Cr-Nb steel is stronger than that of C-Si-Mn-Nb steel,to obtain DP microstructure by coiling at low temperature.C-Si-Mn-Cr-Mo-Nb steel with complex alloying design of high cost is provided with excellent process control stability.Alloy element Mo can promote stabilizing of metastable austenite to obtain F+M DP microstructure by coiling at medium temperature of 600℃.

退火温度对淬火配分后热轧高强钢显微组织和力学性能的影响

将热轧高强钢升温至不同温度(780,810,840,870℃)保温退火600s后进行200℃×60s淬火+410℃×300s配分处理,研究了退火温度对其显微组织和力学性能的影响。结果表明:随着退火温度升高,淬火配分后试验钢中铁素体和马奥岛含量减少,回火马氏体、残余奥氏体和贝氏体含量增加;随着退火温度升高,抗拉强度先减小后增大,屈服强度、断后伸长率、屈强比和冲击吸收功均先增大后减小;840℃退火温度下淬火配分后试验钢的强度、塑性和韧性匹配优异,抗拉强度(830MPa)较大,屈服强度(585MPa)、断后伸长率(39.6%)、屈强比(0.70)和冲击吸收功(-20,-40℃环境下分别为28.35,27.69kJ)最大。

Development of Ti-Microalloyed 600 MPa Hot Rolled High Strength Steel

A high strength steel with yield strength on the order of 600 MPa was developed successfully with only addition of titanium alloying element based on a low-carbon steel. The results showed that the hot deformation accelerated ferrite and pearlite transformation and retarded bainite transformation under continuous cooling condition. The microstructure of this steel was mainly composed of fine grained ferrite and carbides distributing along the ferrite grain boundaries. The yield and tensile strengths of steels were about 620--650 MPa and 720--740 MPa, respectively, and the values of strain hardening exponent and plastic strain ratio were 0.12 and 0.80, respectively, thereby providing a good combination of strength with toughness. In short, the fine grained ferrite and TiC precipitation strengthening contributed to a high strength.

Optimal design of hot rolling process for C-Mn steel by combining industrial data-driven model and multi-objective optimization algorithm

A successful mechanical property data-driven prediction model is the core of the optimal design of hot rolling process for hot-rolled strips. However, the original industrial data, usually unbalanced, are inevitably mixed with fluctuant and abnormal values. Models established on the basis of the data without data processing can cause misleading results, which cannot be used for the optimal design of hot rolling process. Thus, a method of industrial data processing of C-Mn steel was proposed based on the data analysis. The Bayesian neural network was employed to establish the reliable mechanical property prediction models for the optimal design of hot rolling process. By using the multi-objective optimization algorithm and considering the individual requirements of costumers and the constraints of the equipment, the optimal design of hot rolling process was successfully applied to the rolling process design for Q345B steel with 0.017% Nb and 0.046% Ti content removed. The optimal process design results were in good agreement with the industrial trials results, which verify the effectiveness of the optimal design of hot rolling process.

Numerical simulation on recrystallization behavior and microstructure evolution during hot continuous rolling process of 38CrMoAl steel rod

The control of microstructure during hot rolling process of steel is of great importance and will affect the properties of the steel products.According to the production line,a three-dimensional multi-field coupled finite element model of 24-pass continuous hot rolling process of 38CrMoAl steel rod is established using the finite element software MSC.Marc.Based on the recrystallization kinetics model and the grain growth model,a subroutine written in Fortran is introduced to calculate the recrystallization behavior and microstructure evolution of 38CrMoAl steel during the entire rolling process.The distribution and evolution of variables such as strain,temperature and recrystallization fractions during the rolling process are analyzed.The temperature variations and grain sizes at both the center and surface of the tested steel are compared with the experimental results.And it is found that the simulation results are in good agreement with the experimental ones,confirming the reliability of the established model.

Effect of hot/warm roll-forming process on microstructural evolution and mechanical properties of local thickened U-rib for orthotropic steel deck

To improve the strength-toughness of traditional U-rib（ TUR） and solve the problem of insufficient penetration between TUR and deckplate,a new local thickened U-rib（ LTUR） has been proposed to improve the fatigue resistance of the weld joint under the premise of not increasing thickness and strength of the TUR material. And a hot /warm roll-forming process（ RFP） adopting partially induction heating to 700- 1 000℃ was carried out to fabricate LTUR. The deformation behaviors in the forming process and microstructure of LTUR have been investigated.Mechanical properties and fracture mechanism of the LTUR after hot / warm RFP have been systematically discussed. Moreover,the results are compared with those obtained in cold RFP. Mechanical properties of the LTUR deformed above the critical transformation temperature（ A_（c3）） show high performance characteristics with marked fatigue resistance and superior toughness. Upon increasing the heating temperature from 700 to 900 ℃,the initial coarse ferrite-pearlite structure transform into equiaxed ultrafine ferrite（ 1- 3 μm） and precipitates such as（ Nb,Ti）（ C,N） are uniformly distributed in the matrix. The average dislocation density of the specimens after hot rollforming at heating temperature of 900 ℃ decreases dramatically compared with those of the specimens subjected to the cold RFP. Furthermore,a typical characteristic of ductile fracture mechanism and the high impact energy are more convinced that the specimens deformed above 900 ℃ have obtained an optimal combination of strength and toughness.

基于时域卷积网络的精轧出口厚度预测

以精轧过程为研究对象,引入时域卷积网络算法,构建了基于时域卷积网络的精轧出口厚度预测模型。利用时域卷积网络模型提取精轧过程时序数据的特征信息,通过优化模型结构和参数,提升精轧出口厚度预测性能。实际钢种数据集仿真实验结果表明,相较于传统方法,本文所提出的时域卷积网络算法在均方根误差、平均绝对百分比误差及决定系数等评价指标方面存在较大优势,可为现场工程师提供重要的决策信息。

轧钢热装效益的提升探讨

通过提高组织优化、信息化和数字化水平,提出了一系列措施实现资源配置调整、调度协同化、技能培训、引入智能调度系统、数据集成与共享以及数据驱动的决策等,有助于增加企业经济效益,并建议与制造部门密切合作,不断追求优化和改进,旨在提升永钢集团轧钢厂的热装效益。

B500BD13mm带肋钢筋四线切分轧制生产工艺开发

介绍了石横特钢棒材厂英标B500BD13mm热轧带肋钢筋四切分轧制生产工艺的设计。针对顶出口、切分刀粘铁、力学性能不稳定以及成品尺寸不符合标准问题,分别从提高轧机刚性、优化导卫结构、提高温度工艺控制精度和优化孔型、调整机架间张力的措施着手,实现了热轧带肋钢筋四切分的稳定轧制,最终形成工业化批量生产,年创效360万元,产品质量满足用户需求。

90 mm厚工程机械用Q460钢板热轧后的水冷工艺优化

采用低碳和添加铌、钒、钛、铬等微合金元素的成分设计,利用洁净钢冶炼、奥氏体再结晶区粗轧、奥氏体未再结晶区精轧等工艺生产90 mm厚Q460钢板,热轧后采用大流量低辊速控制策略的1次水冷工艺和小流量间断开水控制策略的3次往复式水冷工艺进行水冷,研究不同水冷工艺对钢板组织和力学性能的影响,以获得合适的水冷工艺。结果表明:1次水冷工艺生产的试验钢板的显微组织主要为针状铁素体+少量珠光体,3次往复式水冷工艺生产的试验钢板的显微组织主要为多边形铁素体+珠光体+少量粒状贝氏体;与3次往复式水冷工艺相比,1次水冷工艺生产的试验钢板厚度方向的组织更加均匀、细小,且形成了针状铁素体。2种水冷工艺生产的试验钢板的拉伸性能和冲击韧性均满足标准要求,但是1次水冷工艺生产的试验钢板的−40℃冲击韧性明显优于3次往复式水冷工艺生产的试验钢板,且厚度方向的冲击韧性更均匀。90 mm厚Q460钢板热轧后的合适水冷工艺为1次水冷工艺,所得钢板的屈服强度为495~512 MPa,抗拉强度为604~616 MPa,断后伸长率23%~24%,−40℃冲击吸收功为200 J以上。

紧固件用10.9级32CrB4调质圆钢的开发

通过冶炼过程控制残余w[P]≤0.015%、w[S]≤0.010%,低氧操作稳定控制w[T.O]<10×10^(-6),采用两阶段低温轧制且单道次压下率控制为8%~12%,成功开发出Φ38.8 mm规格具有良好-40℃低温冲击韧性的10.9级32Cr B4螺栓钢。力学性能检验和金相组织观察结果表明,所开发的钢材具有良好的拉伸性能和优良的低温冲击性能,研究出较优热处理工艺为820℃保温水淬后510℃保温回火,室温抗拉强度可达1 075 MPa,-40℃KV_(2)低温冲击平均值可达到53 J,组织以回火索氏体为主,综合力学性能优良,组织均匀性较好。

摩擦对钢退火织构及平面应变影响分析

为进一步提升钢材的轧制效果和质量,在对热轧工艺参数对钢结构影响机理研究的基础上,通过实验研究了摩擦对钢退火结构的影响,得出了润滑轧制工艺下主要成分为γ纤维织构,无润滑轧制工艺下主要为高斯织构。通过数值模拟仿真研究了不同摩擦系数对应板材的等效塑性变形、全塑性变形的变化,研究成果可指导后续实践生产。