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 iow-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.

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.

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.

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.

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.

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.

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.

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。

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。

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。

大跨度连续钢箱梁悬索桥无索区钢梁施工控制技术

秀山大桥为主跨926 m的三跨连续弹性支承体系钢箱梁悬索桥,无索区梁段采用临时高支架+永久吊索法拼装,支架采用“钢管支架+纵移轨道”形式。采用MIDAS Civil软件建立主桥有限元模型,基于无应力曲率的全过程迭代法进行施工控制计算,确定无索区梁段支架预抬量和无索区梁段拼装线形,以及支架反力和索梁内力。通过计算,官山侧桥塔无索区梁段支架预抬量最大值0.625 m、最小值0.600 m,无索区梁段理论线形与设计值最大偏差-4 mm,支架各支点反力均匀,钢箱梁合龙后第1对吊索索力仅增大4.5%,无索区梁段内力变化较小。钢箱梁施工时,利用缆载吊机荡移法起吊无索区梁段至预定位置,采用液压千斤顶和移位器调整无索区梁段支架预抬量和梁段间拼装线形;利用缆载吊机起吊无索区相邻的第1对吊索梁段并与之精调连接,整体环焊结束后拆除支架。无索区梁段支架拆除后实测高程最大偏差-7 mm,桥面纵坡最大偏差-0.0373%,满足设计要求;成桥后钢箱梁纵坡最大偏差0.264%,成桥线形平顺光滑。

汽车大梁钢控氮工艺的优化

氮元素是钢中典型的有害元素,在结晶过程中,钢中氮的溶解度急剧降低,析出氮化铁(FeN、Fe 4N)位于晶界上阻止位错移动,虽可提高钢的强度和硬度,但会严重降低钢材塑性,易在后期加工过程出现开裂现象,同时氮含量易与钢中钛发生反应,降低有效钛,降低钢材性能。本文介绍了工业生产全流程氮含量变化,分析了钢中氮含量升高的主要因素并制定整改措施。通过明确转炉铁水、石灰、合金等原辅料的入炉标准,优化转炉吹炼枪位和炉后脱氧工艺,同时提高精炼埋弧效果,稳定控制大梁钢成品氮含量≤45 ppm,合格率达到95%。

钢材深加工过程控制系统建设

钢材深加工过程控制系统的建设对于提高钢材加工质量、降低生产成本和提高生产效率具有重要意义。以钢材深加工过程控制系统的建设为研究对象,通过对相关文献的梳理和分析,探讨了系统的基本原理、关键技术以及在实际应用中的作用和效果。研究发现,钢材深加工过程控制系统能够实现对加工过程的实时监控和控制,提高产品质量、降低废品率和减少能耗。然而,在实际应用中还存在一些问题和挑战,如系统的稳定性、数据的准确性和设备的兼容性等。因此,进一步推进钢材深加工过程控制系统的建设,需要加强技术研发、加强数据管理和加强设备改造等方面的工作,以提升钢材深加工的智能化水平。

CrMo系合金结构钢的开发

采用顶底复吹转炉冶炼-LF精炼-VD真空处理-连铸-圆棒轧制工艺成功开发CrMo系合金结构钢,其化学成分、夹杂物控制水平、力学性能等各项指标均满足标准要求。结合生产实际,对CrMo系产品技术要求、工艺控制要点、试制结果进行了分析与介绍。

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。

波浪形钢桁架复杂节点焊接施工及质量控制技术

厦门某新建高铁站站房工程的屋盖主体为大跨度高空间波浪形钢桁架结构,屋盖主要采用管桁架结构体系,结构最大高度55.50 m。支撑钢柱主要为6根大截面十字钢骨柱转组合开花柱,开花柱的四角钢柱与中部钢柱一起延伸至屋盖底部,并通过铸钢件与屋盖桁架连接,开花柱与屋盖桁架连接节点涉及多种不同等级钢材、管径及壁厚的杆件与铸钢件对接,并且存在箱型构件与铸钢件对接,连接节点复杂繁密。文章通过对复杂节点进行建模分析并结合工艺特点进行深化设计,制定了一套可行性高,实用性强的专项焊接工艺,实现在高效施焊的同时确保焊接质量的稳定可靠。

集聚式多锚头钢横梁制造工艺研究

池州长江公路大桥主塔采用花瓶形,塔柱间钢横梁采用集聚式多锚头箱形结构,每个钢横梁上最多有10对锚固点(20个锚头)。通过对集聚式多锚头钢横梁的结构特点分析,确定了合理的横梁块体组装焊接顺序;通过焊接工艺评定试验确定了与母材匹配的焊接材料和焊接参数,保证了焊缝质量;通过对拼装胎架、锚箱精度控制、焊接变形控制等关键项点研究和有效技术措施的应用,确保钢横梁的外形尺寸符合标准和规范要求;先孔法栓接技术的实施,可大幅提高桥位钢横梁拼装效率。

BS700高强钢臂架焊接工艺研究

结合生产实际,通过对BS700高强钢试件的焊接试验和BS700高强钢臂架的焊接实践,从焊接工艺方法、焊缝的外观检查、超声波检测、力学性能检测,以及BS700高强钢臂架焊接生产的焊接变形控制、焊后质量检测等多方面进行了阐述,提供了一种BS700高强钢臂架的焊接工艺方法,为同类产品的工艺实践提供参考。