高温渗碳齿轮钢的研究进展

常用齿轮钢渗碳温度为930℃,提高渗碳温度至1000～1050℃能显著缩短渗碳时间,但易引起晶粒长人,因此发展了通过Nb、Ti、B微合金化,细化钢原奥氏体晶粒的高温渗碳齿轮钢。文中介绍了国内外高温渗碳齿轮钢的钢种成分、工艺特点、高温渗碳层组织控制和钢的疲劳性能的研究进展。     

高强度汽车渗碳齿轮钢的发展及应用

渗碳齿轮钢是汽车用主要结构钢之一，国内主要汽车生产厂家的高强度齿轮钢材料一直使用不同国家多个牌号的渗碳钢。随着技术和应用的发展有必要开发新品种的高强度齿轮钢。分析了高强度汽车渗碳齿轮钢在国内外的发展及应用现状，并根据我国合金材料的特点展望了其发展趋势。     

高温渗碳齿轮钢的晶粒粗化行为

  为了开发适合980 ℃高温渗碳的齿轮钢，利用伪渗碳方法，研究了铌质量分数为0、0.036%、0.060%和0.100%的18Cr2Ni2Mo渗碳齿轮钢在930和980 ℃的晶粒粗化行为。结果表明，由于析出NbC钉扎晶界，铌微合金化可以显著细化试验钢在930和980 ℃奥氏体化后的晶粒尺寸，且随着铌质量分数增加，铌微合金化明显抑制试验钢在980 ℃长时间奥氏体化晶粒粗化倾向。添加0.100%Nb的18Cr2Ni2Mo齿轮钢在980 ℃奥氏体化20 h后，平均晶粒尺寸仍然在26 μm左右，适合于980 ℃高温长时间渗碳。     

大口径无缝钢管淬火设备的设计与改进

介绍扬州诚德铜管有限公司大口径无缝铜管热处理生产线的淬火设备。该设备在研发设计过程中,采用了国内外先进的“外淋＋旋转＋内喷＋喷雾”的淬火工艺,以满足一些特种钢管淬火要求。通过对该淬火设备的工作原理、淬火工艺、结构特点的分析,说明了该设备改进后与原有淬火设备在机械结构、淬火效果、力学性能等方面的不同。生产实践表明,该新增淬火设备具备提升产品附加值的能力。     

40Cr钢方坯表面淬火工艺及组织转变规律

热送裂纹限制了热送技术的推广应用,而表面淬火技术可以有效改善热送裂纹的质量问题.以某钢厂180 mm×180mm断面小方坯连铸机为对象,40Cr钢为淬火试验钢种,通过开展现场离线淬火试验研究,并利用光学显微镜(OM)及数值仿真技术,进行显微组织分析与淬火-自回火过程传热分析,研究了表面淬火对铸坯表层组织转变的影响规律....     

预备热处理对A-F区亚温淬火-回火的42CrMo钢组织和性能的影响

利用金相显微镜、洛氏硬度计和扫描电镜,对经过预备热处理(退火、淬火、调质)+亚温淬火+高温回火处理(又称临界区淬火+回火)后的42CrMo钢的组织、冲击性能以及断口形貌进行了观察和分析。结果表明,预备热处理为退火处理时,亚温处理后残留的铁素体粗大不均;且在回火索氏体之间分布不均匀;预备热处理为淬火处理和调质处理时,残留的铁素体形态细小,且与回火索氏体均匀分布。采用不同预备热处理时,亚温处理后的硬度差别很小。亚温处理后42CrMo钢的冲击性能均高于常规调质处理后的冲击性能;预备热处理为调质处理时,亚温处理后的冲击功最大,从其断口形貌中可以看出,其起裂区和裂纹纤维扩展区所占比例较退火处理和淬火处理时要大。因此,调质处理更适合作为42CrMo钢的预备处理。     

Experimental and Numerical Evaluation of the Heat Transfer Coefficient in Press Hardening

When producing thin ultra high strength steel components with the press hardening process, it is essential that the final component achieves desirable material properties. This applies in particular to passive automotive safety components where it is of great importance to accurately predict the final component properties early in the product development process. The transfer of heat is a key process that affects the evolution of the mechanical properties in the product and it is essential that the thermal contact conditions between the blank and tool are properly described in the forming simulations. In this study an experimental setup is developed combined with an elementary inverse simulation approach to predict the interfacial heat transfer coefficient (IHTC) when the hot blank and cold tool are in mechanical contact. Different process conditions such as contact pressure and blank material (22MnB5 and Usibor 1500P) are investigated. In the inverse simulation, a thermo‐mechanical coupled simulation model is used with a thermo‐elastic‐plastic constitutive model including effects from changes in the microstructure during quenching. The results from simulations give the variations of the heat transfer coefficient in time for best match to experimental results. It is found that the pressure dependence for the two materials is different and the heat transfer coefficient is varying during quenching. This information together with further testing will be used as a base in a future model of the heat transfer coefficient influence at different conditions in press hardening process.     

中锰钢的研究进展与前景

总结了国内外中锰钢研究现状, 对文献中中锰钢的成分设计、成型工艺、热处理工艺、组织性能调控等进行汇总分析, 得到了合金元素、成型工艺、微观组织结构和热处理对力学性能的影响规律, 并对中锰钢的性能例如lüders带和PLC带对加工硬化率的影响、氢致延迟开裂性能给予了重点关注和讨论; 同时提出借鉴第二代先进高强钢(纯奥氏体相)"层错能"这一控制形变模式的概念, 对中锰钢中奥氏体相的形变模式提出预测; 最后对目前中锰钢研究的争议问题、发展前景及未来可能面对的问题进行阐述.      

Study on microstructure and mechanical properties of martensitic stainless steel 6Cr15MoV

Martensitic stainless steel containing 12%-18%Cr have high hardness due to high carbon content. These steels are common utilized in quenching and tempering processes for knife and cutlery steel.The properties obtained in these materials are significantly influenced by matrix composition after heat treatment,especially as Cr and C content.Comprehensive considered the hardness and corrosion resistance,a new type martensitic stainless steel 6Cr15MoV has been developed.This study emphatic researches the effect of heat treatment processes on microstructure and mechanical properties of 6Cr15MoV martensitic stainless steel.Thermo-Calc software has been carried out to thermodynamic calculation;optical microscope（OM）,scanning electronic microscope（SEM） and transmission electron microscope（TEM） have been carried out to microstructure observation;hardness and impact toughness test have been carried out to evaluate the mechanical properties.Results show that the equilibrium carbide in 6Cr15MoV steel is M₂₃,C₆ carbide,and finely distributed of M₂₃C₆ carbides can be observed on annealed microstructure of 6Cr15MoV stainless steel.6Cr15MoV martensitic stainless steel has a wider quenching temperature range,the hardness value of steel 6Cr15MoV can reach to 60.8 -61.6 HRC when quenched at 1060 - 1100℃.Finely distributed carbides will exist in quenched microstructure,and effectively inhabit the growth of austenite grain.With the increasing of quenching temperature,the volume fraction of undissolved carbides will decrease.The excellent comprehensive mechanical properties can be obtained by quenched at 1060-1100℃with tempered at 100-150℃,and it is mainly due to the high carbon martensite and fine grain size.At these temperature ranges,the hardness will retain about 59.2-61.6 HRC and the Charpy U-notch impact toughness will retain about 17.3-20 J.The morphology of impact fracture surface of tested steel is small dimples with a small amount of cleavage planes.The area of cleavage planes increases with the increasing of tempering temperature.     

Mn2钢低温韧性变化规律研究

对Mn2钢在不同热处理工艺、不同试验温度和不同试样状态下的冲击韧性进行了详细的分析,结果表明:CM690钢在900℃保温90 min水冷淬火,600℃保温90 min水冷回火,在保证钢材的强度满足要求的情况下,可获得良好的韧性;淬火水温超过30℃时,因钢的淬透能力下降,会强烈地降低钢的强度和韧性;钢中加入0.015%~0.025%的Ti,提高冲击韧性值35~40 J;对于CM490钢,若轧后空冷或堆冷,由于冷却速度较低,会获得铁素体+珠光体+贝氏体的混合组织,不利于提高钢材的韧性,而正火后其组织为铁素体+贝氏体,其冲击值比前两种状态高3~5倍。     

Modeling the Case Hardening of Automotive Components

A generalized framework has been developed within ABAQUS to model the surface hardening heat treatment processes for automotive steel components. The macro-scale heat transfer and stress calculations during the heating and quenching are coupled with the microstructural phase calculations, defined through a user routine, to estimate key process parameters such as case depth and surface hardness. This model has been applied to predict these parameters in two key industrial processes, i.e., case hardening of crankshafts and case carburization of gears. The results of the case depth and hardness calculations have been validated with the literature and in-house plant data. The effect of varying quench conditions on the overall stress distribution changes within the component has been outlined.     

Numerical Simulation on Carburizing and Quenching of Gear Ring

 The carburizing process of the gear ring was simulated by taking into account the practical carburizing and quenching techniques of the gear ring and by solving the diffusion equation. The carbon content distribution in the carburized layer was obtained. Based on the results, the quenching process of the gear ring was then simulated using the metallic thermodynamics and FEM; it was found that the carburization remarkably affects the quenching process. Microstructures and stress distributions of the gear ring in the quenching process were simulated, and the results are confirmed by experiments.     

Development of TP310HCbN(07Cr25Ni21CbN) austenitic stainless steel tubes

Improving the unit heat efficiency,reducing coal consumption and the emission of CO₂ and meeting the requirements of environmental protection and energy conservation is the goal of the boiler and the power industry.Developments of large capacity and high parameter ultra-supercritical（USC） units are the tendency of the power industry.There is no doubt that the development of USC units is based on the development of materials, especially the materials used for super-heater and reheater in high-temperature USC boiler.Due to the long time exposure to the harsh environment,such as bearing the 600℃steam oxidation,and withstanding the corrosive flue gas and fly ash erosion,the materials require not only good high-temperature strength,but also a good corrosion resistance.In consideration of the requirements cited above,foreign countries had developed TP310HCbN （07Cr25Ni21CbN） austenitic heat-resistant steel.However,the domestic demands for this material still depend on import and the cost is high,so the boiler and the power industry expects eagerly that these steels can be produced by domestic metallurgical industry,especially Baosteel,to replace the imported products.In order to satisfy the requirements of domestic manufacturing super-heater and reheater used in ultra-supercritical power boiler,after developed T23、T91、T92、S30432 high pressure boiler tube,Baosteel began to develop TP310HCbN （07Cr25Ni21CbN）austenitic stainless steel tube in January of 2007.This study describes the composition design, the manufacturing process of product,and the assessment of performance of Baosteel’s TP310HCbN （07Cr25Ni21CbN）.The data indicates that properties of Baosteel’s TP310HCbN（07Cr25Ni21CbN） conform to the ASME SA-213 standard and GB5310 standard,so it can substitute the imported products and is suitable for manufacturing power station boiler of great capacity and high steam parameters.     

New Developments in Non‐destructive Testing for Quality Assurance in Component Manufacturing

Within the scope of the research centre (CRC 489) “Process chain for manufacturing precision forged high performance components”, highly loaded functional surfaces such as gear teeth and bearing seats of gearwheels, gear shafts and crankshafts are quenched from the forging heat using newly developed water‐air spray cooling in a computer controlled nozzle array. Here, the water‐air flow is time‐controlled so that the desired surface properties such as hardness value and depth are obtained. However, hardening cracks due to the quenching process or microstructural changes must in any event be avoided since these lead to crack growth and component failure subject to loading. The aim of the sub‐project “Non‐destructive component testing” is to develop a new innovative non‐destructive testing method for monitoring the process and for quality assurance in the process chain of precision forging. This comprises non‐destructively characterising the material properties for determining the hardness parameters in the bearing and gear‐tooth regions following heat treatment and hardfinishing as well as rapidly testing for defects in functional surfaces. Within the framework of a structural reliability test, the component properties are assessed using the newly developed techniques for the early detection of failures, their localisation and the failure diagnosis by accurately monitoring the development of damage as well as estimating the residual service life.     

Steel’s CO2 balance—a contribution to climate protection

Steel making is energy and material intensive.That is why steel is always demonized and confronted with incriminations and requirements for reduction of its environmental impact.Those pure demands-like for emission trading are short-sighted as they do not base on an integrated approach.Instead they merely consider CO₂ emissions during the production process.A forward-looking,global climate and environmental policy needs a sustainable life cycle approach.Therefore it must for example also take into account the contribution of steel towards cutting emissions in its application-in the energy.automotive and household sectors.Steel will play a key role in climate protection. One-third of the remaining CO₂ reduction target planned in Germany by 2020 can only be achieved with the help of innovative steel products and their applications.This is the conclusion of an independent study by The Boston Consulting Group（BCG） on behalf of Steel Institute VDEh,and German Steel Federation.The study compares CO₂ savings from important innovative steel applications（such as more efficient power stations,wind turbines,or lighter vehicles） with CO₂ emissions caused by steel production. By adopting this comprehensive perspective,the study for the first time provides a CO₂ balance for the material steel by comparing the CO₂ reductions made possible through innovative steel applications with the CO₂ emissions resulting from steel production.The balance was calculated on the basis of eight selected innovative steel applications in Germany for the period 2007 to 2020,whereby the CO₂ emissions caused by steel production were considered throughout the entire life cycle of the particular steel use.For the selected examples,the use of innovative steels resulted in a total savings potential of 74 Mt of CO₂ in 2020.The calculations are based on conservative assumptions;for example without counting of potentials by exported steel or by comparison with competitive materials. The production of steel in Germany,including the extraction of raw materials,transports and further processing, causes annual emissions of approx.67 Mt CO₂ This can be more than compensated by the above mentioned CO₂ savings.The balance is even more positive if one only considers the emissions of about 12 Mt/a CO₂ caused by the selected eight steel applications.Innovative steel use thus saves six times as much CO₂ as is generated by its production. Steel is part of the story and helps to achieve CO₂ reduction targets.On this basis the steel industry should start up with a new global approach to be accepted as a CO₂ killer,too,instead of being the devil.This needs a political discussion on an integrated approach taking into account the whole life cycle,which finally can lead away from stringent emission caps or incompatible emissions trading systems for the different regions.     

60kg汽车用热轧高扩孔钢生产与应用

针对传统60 kg高强钢无法满足特殊用户使用要求的现状,宝钢采用低碳低硫的成分及特定的精炼方式,结合特殊的热轧工艺,开发出一种新型60 kg高扩孔钢。通过比较分析60 kg高扩孔钢和传统60 kg高强钢的化学成分、生产工艺、金相组织、力学性能,发现高扩孔钢具有更好的综合力学性能。扩孔裂纹传播特征及扩孔裂纹扩展的机理分析表明,由于传统高强钢存在珠光体及带状特征,加速了扩孔裂纹的萌生及快速扩展;而高扩孔钢以多边形铁素体为主,有效阻碍了裂纹的扩展,因此组织均匀性是获得高扩孔率的关键因素之一。最后,以车轮轮辐为例介绍60 kg高扩孔钢的应用,60 kg高扩孔钢冲压轮辐中心孔及螺栓孔等关键部位成形良好,并通过用户成形认证。     

钛合金齿轮的表面处理与应用

主要介绍了钛合金齿轮在制造过程中关键的表面处理技术,结合钛合金齿轮在运行过程中的受力特征及钛合金表面无氢渗碳层的结构特点,在其表面制备出TiC+Ti扩散层,不仅提高了齿面的耐磨性能,而且也提高了齿面抗冲击载荷的能力。通过无氢渗碳、热处理及机械加工工序的有效协调,制造出的钛合金齿轮耐磨性能优良、抗冲击振动性能良好、噪声低,已经平稳运行16年。     

20CrH温锻内星齿轮混晶原因分析及工艺改进

特钢厂生产的20CrH特殊钢棒材，下游用户温锻制作内星轮后，经965℃×6 h渗碳热处理后发现混晶现象。采用光学显微镜观察并设计热处理试验验证，结果表明：锻造变形温度不均及锻后保温温度偏低，导致在后续渗碳过程中局部奥氏体晶粒出现异常长大而产生混晶。将内星轮温锻后保温温度由710℃提高至900℃,能有效改善混晶现象，为同类特殊钢零部件温锻的工艺设计提供指导。     

P110(27CrMo)钢级石油套管热处理工艺研究

为了获得27CrMo钢种升级为P110钢级套管的最佳热处理工艺,研究了热处理工艺对27CrMo力学性能和冲击性能的影响。研究结果表明,淬火温度和淬火保温时间对实验钢的拉伸性能影响不大,其对实验钢的冲击性能影响较大,实验钢的冲击功随着淬火温度的升高呈两段上升趋势,而随着淬火保温时间的延长呈上升趋势;随着回火温度升高,实验钢的屈服强度和抗拉强度呈下降趋势,而伸长率和冲击功均呈上升趋势。     

中板生产线轧后先进冷却系统的研发及应用

为满足高品质节约型中厚板产品的生产需求,降低生产成本,提高产品效益,提升企业竞争力,2012年东北大学轧制技术及连轧自动化国家重点实验室（the State Key Laboratory of Rolling and Automation, RAL）为南钢2800mm中板生产线新建一套具备常规加速冷却（Accelerated Cooling,ACC）功能、超快速冷却（Ultra—fastCooling,UFC）功能、直接淬火（DirectQuenching,DQ）功能的多功能轧后先进冷却装置（Advanced Cooling System for Plate Mill,ADCOS-PM）以及与之相配套的水处理系统和预矫直系统。在此基础上,以新一代控制轧制控制冷却技术（New Generation Thermo—Mechanical Control Process,NG—TMCP）为指导,充分发挥ADCOS—PM系统的技术装备优势,使低成本高强低合金钢、高强工程机械用钢、管线钢以及低温容器钢等一系列高品质节约型中厚板产品得到开发和应用。