Modeling of Microstructure Evolution and Mechanical Properties of Steel Plates Produced by Thermo-Mechanical Control Process and Its On-line Application

An integrated metallurgical model was developed to predict microstructure evolution and mechanical properties of low-carbon steel plates produced by TMCP. The metallurgical phenomena occurring during TMCP and mechanical properties were predicted for different process parameters. In the later passes full recrystallization becomes difficult to occur and higher residual strain remains in austenite after rolling. For the reasonable temperature and cooling schedule, yield strength of 30 mm plain carbon steel plate can reach 310 MPa. The first on-line application of prediction and control of microstructure and properties (PCMP) in the medium plate production was achieved. The predictions of the system are in good agreement with measurements.

Controlled Rolling and Cooling Process for Low Carbon Cold Forging Steel

Effect of controlled rolling and cooling process on the mechanical properties of low carbon cold forging steel was investigated for different processing parameters of a laboratory hot rolling mill. The results show that the specimens with fast cooling after hot rolling exhibit very good mechanical properties, and the improvement of the mechanical properties can be attributed mainly to the ferrite-grain refinement. The mechanical properties increase with decreasing final cooling temperature within the range from 670 ℃ to 570 ℃ due to the finer interlamellar spacing of pearlite colony. The specimen with fast cooling after low temperature rolling shows the highest values of the mechanical properties. The effect of the ferrite grain size on the mechanical properties was greater than that of pearlite morphology in the present study. The mechanical properties of specimens by controlled rolling and cooling process without thermal treatment were greatly superior to that of the same specimens by the conventional rolling, and their tensile strength reached 490 MPa grade even in the case of low temperature rolling without controlled rolling. It might be expected to realize the substitution medium-carbon by low-carbon for 490 MPa grade cold forging steel with controlled rolling and cooling process.

Change and control of nitrogen in molten steel production process

The change and control of nitrogen content in molten steel was investigated through the production process of "LDBAr-LF-RH-CC". Results show that nitrogen content reduces gradually in converter-steelmaking stage, rises rapidly from the end of converter process to the end of argon station process, continues to increase in ladle furnace process, and decreases slightly in RH refining stage. Since nitrogen is removed mainly by BOF steelmaking and vacuum refining operations, nitrogen in molten steel should be removed as much as possible in these two operations. However, nitrogen uptake should be minimized in other operations of molten steel production process.

Construction and alignment control of the middle steel pylon of Taizhou Bridge

The general construction procedure of the steel middle pylon is briefly introduced. The alignment control of the pylon is carried out during the whole process of the construction. The control concept is extended to the manufacture stage. The manufacturing alignment error is strictly controlled in the segments precast process in factory, and the error is recognized and predicted precisely during the installation stage. The adjusting joints are employed to amend the accumulated error, which ensure that the steel pylon alignment could satisfy the precision requirements after installation.

Developing of robot flexible processing system for shipbuilding profile steel

A robot flexible processing system of shipbuilding profile steel was developed. The system consists of computer integrated control and robot. An off line programming robot was used for marking and cutting of shipbuilding profile steel. In the system the deformation and position error of profile steel can be detected by precise sensors, and figure position coordinate error resulted from profile steel deformation can be compensated by modifying traveling track of robotic arm online. The practical operation results show that the system performance can meet the needs of profile steel processing.

IMPROVED PROCESSING FOR MICROSTRUCTURES AND MECHANICAL PROPERTIES OF A COMMERCIAL PIPELINE STEEL

The transformation productions of hot-deformation simulation experiments were investigated using a Gleeble-1500 hot simulator for a commercial pipeline steel. Based on the investigation results, the improved thermo-mechanical control processing (TMCP) schedules containing a two stage multi-pass controlled rolling coupled with moderate cooling rates were applied to hot rolling experiments and acicular ferrite dominated microstructure was obtained. Microstructures and mechanical properties of hot rolled plates were related to TMCP processing, and regression equations describing the relation between processing parameters and mechanical properties in the current TMCP were developed, which could be used to predict mechanical properties of the experimental steel during commercially processing. It was found that with an increase in cooling rate after hot rolling, grain size in the microstructure became smaller, the amount of polygonal ferrite decreased and acicular ferrite increased, and accordingly mechanical properties increased.

A review on the current status of Fe-Al based ferritic lightweight steel

There is an ever-growing demand for lightweighting of steel for structural applications,particularly for automobile and transportation applications.It is mainly to improve the fuel efficiency,reduce the CO_(2) emissions and cater the increased passenger safety.Hence,the main focus is to reduce the density of the steel structure without affecting other properties.This can be achieved by down-gauging of the conventional steel by replacing the steel with higher strength,however,it is limited by dent resistance and stiffness.So,the novel idea is to reduce the density of the steel itself.It is well-known that addition of Al to steel reduces the density of the steel.About 1wt% of Al addition to steel can reduce the density by 1.3%,decreases the elastic modulus by 2% and it improves the strength by about 40 MPa.There is a new class of low-density/lightweight steel with addition of about 6-9 wt% Al to steel.Addition of higher than 9 wt%of Al in steel leads to embrittlement issues due to ordering and environmental effect.These disordered Fe-Al lightweight steels have raised considerable interest due to their low-density,high ductility,costeffectiveness and feasibility for bulk production.The low-density steels are envisaged in the development of an advanced lightweight ground transportation system,huge structures and also for certain defence applications and in thermal power plants.

Study on gas metal arc welding of two types of TMCP steels

Gas metal arc welding experiments were conducted on two types of steels with 0.41% carbon equivalent(Ceq) and 0.31% Cequsing WER70T wire and 20% CO_(2)and 80% Ar as shielding gas.The two types of steels show satisfactory weldability.The transition temperatures of 50% upper shelf energy(Tk0.5) for Charpy-V impact test of both the welded joints are below-40 ℃.However, the toughness of the fusion line zone and heat-affected zone(HAZ) of the two steel joints exhibits differences, with the toughness of 0.41% Ceqsteel being better than that of 0.31% Ceqsteel.The Tk0.5of the fusion line zone and the HAZ of 0.41% Ceqsteel is below-60℃,whereas that of 0.31% Ceqsteel is above-40℃.The welded joint of 0.41% Ceqsteel has low hardness fluctuation, while that of 0.31% Ceqsteel exhibits a narrow, softened zone, which has no obvious influence on the tested tensile strength.The coarse grain heat-affected zone(CGHAZ)microstructure of 0.41% Ceqsteel is bainite, while that of 0.31% Ceqsteel is bainite with ferrite and minor pearlite.

TMCP工艺下Q390钢板厚度、温度场与组织演变的关系

采用TMCP工艺制备三种不同厚度的Q390热轧钢板,基于冷却温度场有限元分析揭示了厚度对组织演变和硬度的影响规律。结果表明:在相同冷却条件下,40 mm厚热轧钢板厚度方向组织存在明显差异,即边部以贝氏体为主,而心部为铁素体和珠光体,对应显微硬度差值约40 HV;13、20 mm厚热轧钢板厚度方向组织较为均匀,以贝氏体为主,显微硬度分布也相对均匀。温度场有限元分析表明厚板(40 mm)试样的心部组织铁素体+珠光体主要形成于空冷阶段;而对于其他厚度钢板,在水冷阶段,心部和边部获得较为一致的终冷温度和冷速,且均在贝氏体相变温度区间。

Effect of M-A constituents formed in thermo-mechanical controlled process on toughness of 20CrNi2MoV steel

The effect of martensite–austenite(M–A)constituents formed in thermo-mechanical controlled process on impact toughness of 20CrNi2MoV steel was investigated.The variation in fraction,size and morphology of M–A constituent and its effect on toughness under different cooling rates were carried out.The result shows that there was no significant change in the fraction of M–A constituent under different cooling rates,but the distribution and size of M–A constituent were greatly influenced by cooling rate,which consequently influenced toughness.The amount of large blocky M–A constituents decreased from 4.7%to 1.7%,while that of elongated M–A constituents increased from 3.8%to 8.6%with the cooling rate increasing from 7 to 26°C/s,and the corresponding impact energy decreased from 132 to 84 J.The deterioration of impact toughness could be related to the increase in the elongated M–A constituents.The elongated M–A constituents existing along the prior austenite grain boundaries in samples of 26°C/s could easily lead to the formation of cleavage crack,which then results in the lower crack initiation energy than that of low cooling rate samples.

Microstructure and mechanical properties of a Cr-Ni-W-Mo steel processedthermo-mechanical controlled processing

Experiments were conducted to evaluate the microstructure and tensile properties of a medium carbon Cr-Ni-W-Mo steel processedthermo-mechanical controlled processing(TMCP)with cooling at different conditions in water,oil,air or lime followedlow tempering.Compared to normal heat-treatment processing,TMCP with water-cooling after deformation enhances the yield strength and tensile strength of the steelabout 323 MPa and about 251 MPa,respectively,due to higher dislocation strengthening and grain boundary strengthening.Meanwhile,it increases the elongation by ;about 1.76%attributed to the increase in volume percentage of the retained austenite and the refined laths of tempered martensite.Slowing the cooling rate after deformation during TMCP leads to a decrease in the strength.This results the coupling effectsthe reduction in dislocation density and volume fraction of tempered martensite together with the coarseness in martensite sizes.However,cooling rate decreasing has less influences on ductility becathe improved elongation the increase in the volume fractions of both retained austenite and lower bainite together with dislocation density decreasing is compensatedthe reduced elongation coarsened grains.

转炉炼钢几个关键技术的研究进展

转炉炼钢作为世界上冶炼高品质钢的主要炼钢方法,其技术的进步与发展对钢铁行业节能减排、降本增效具有巨大的推动作用。介绍了我国转炉炼钢几个关键技术的研究及进展。通过从理论分析和实践探索两个方面研究了废钢的熔化行为,揭示了废钢熔化机理;分析和总结了喷吹方式、底吹工艺等对转炉熔池流动特性的研究;从冶金机理和数据模型两个方面介绍了转炉终点控制技术的发展现状和展望;最后从整体优化冶金流程角度出发,从数学建模到平台仿真介绍了炼钢-精炼-连铸一体化技术进展以及存在问题。转炉智能化发展需要更多的设备、方法和技术的支撑,转炉智能化炼钢是涉及冶金、自动化、计算机等多学科的综合实践应用案例。

高牌号无取向硅钢生产流程中织构控制研究现状

在节能减排的背景之下,水电、风电和核电等清洁能源行业得到了快速发展。高牌号无取向硅钢是上述发电机组应用最普遍的铁芯材料。因此,开发低铁损和高磁感的高牌号无取向硅钢是清洁能源产业高质量发展的前提条件。织构是影响高牌号无取向硅钢磁感和铁损的主要因素之一,受到生产工艺的影响。然而,高牌号无取向硅钢工艺流程长,影响织构控制的工艺因素众多。为了满足高牌号无取向硅钢在低铁损时实现高磁感,在产品加工时应尽量避免对磁性能不利的{111}织构的形成,促进对其有利的{100}和{110}织构形成。本文首先介绍了高牌号无取向硅钢的工艺流程,对比了国内外钢铁企业产品的磁性能(P_(15/50)和B_(50))。其次,阐述了高牌号无取向硅钢在炼钢、热轧、常化、冷轧和成品退火过程中促进有利织构形成的影响因素。最后,归纳出能促进高牌号无取向硅钢有利织构形成的生产工艺,并对织构控制的发展方向提出了建议。

高成材率钢锭缺陷控制技术及其研究进展

钢锭凝固过程中将不可避免地产生各类缺陷,严重制约了钢锭成材率,直接影响后续加工工艺和最终产品质量。抑制缺陷形成、探索创新并有效改进模铸工艺对提高钢锭成材率具有重要意义。通过探讨和分析关于提高钢锭成材率的研究现状和最新进展,包括锭型设计、工艺参数优化、先进铸造技术等,展望了多相流动控制、微观结构调控和冷却速率精准管理等未来模铸与凝固技术研究发展方向,为实现高成材率钢锭的稳定生产提供了合理化建议。

大截面圆端形钢壳塔锚固节段制造工艺

安罗高速黄河特大桥索塔在国内首次采用无纵筋圆端形大截面钢混组合结构,针对钢壳塔锚固节段结构特点与制造难点,介绍了其总体制造工艺,采取了一系列控制措施,解决了钢壳塔锚固节段制造线形控制、精度控制、焊接变形控制等诸多技术难题。

全钢载重子午线轮胎胎圈露线的原因分析及解决措施

从产品设计和工艺控制方面分析全钢载重子午线轮胎胎圈露线的原因,并提出相应的解决措施。通过适当增大成型平面宽和鼓肩宽,适当减小钢丝圈内侧胎侧厚度和胎趾角度,严格控制胎侧成型定位、胎坯存放、硫化机机械手精度、钢丝圈缠绕工艺及存放等措施,有效地解决了全钢载重子午线轮胎胎圈露线问题,提高了轮胎的安全性能,降低了生产成本。

薄壁大口径钢管弯管成型变形控制工艺

制作超轻越野车车身骨架的钢管因材质特殊、口径大、管壁薄,弯管成型后截面变形严重,导致尺寸严重超差,严重影响车身整体尺寸精度和结构强度。对此,进行原因分析,并提出薄壁大口径钢管弯管成型变形控制工艺。介绍了工艺原理和应用效果。这一工艺可以减小薄壁大口径钢管弯管成型的截面变形量。

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。

跨江大桥智能钢筋加工厂设备的应用研究

针对张靖皋长江大桥南航道桥南锚碇钢筋加工厂生产需要,对钢筋加工设备和起重机进行智能化升级。文中通过物流转运装置和光电控制系统对传统钢筋加工设备进行自动化升级改造,集成自动上料机和自动剪切线,基于钢筋云平台与上位机控制系统串联各生产线顺序功能,实现了钢筋从上料、切断到加工的连续自动化生产。通过设置位置传感器和多点工位呼叫台对起重机进行智能化升级,采用智能算法对起重机的避碰和调度功能进行优化,实现了起重机的自动化调度,提高了起重机运行的效率。最后,通过现场应用验证了设备升级方案的可行性,既降低了工程成本,又提高了生产效率。

高级别管线钢板形控制技术研究

随着管道输送效率的不断提高,大厚壁大口径高钢级已成为管线钢发展的趋势。为满足高强韧性要求,合金加入量及轧制工艺难度越来越大,终冷温度控制朝着大冷速超低温控制,造成钢板内组织及应力不均性增大,板形控制难度增加,瓢曲严重。为解决此类问题,通过对钢坯加热制度、初轧工艺、精轧工艺、冷却参数以及成分设计等实际生产数据统计分析,确定板形影响关系,为控制高级别管线钢板形问题制定有效措施。