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。

中碳CrMo钢中Ti、Nb液析形貌及生成机理分析

通过观察微合金Ti、Nb、V在42CrMo钢连铸坯中的液析形貌,以及液析经加热轧制后的变化,同时,采用热力学计算的方式推导液析生成机理。结果表明,在含w[Ti]0.012%、w[Nb]0.030%、w[V]0.030%、w[N]0.003 5%的42CrMo钢410 mm×530 mm连铸坯中,可观察到Ti、Nb以复合碳氮化物的形式析出,形成微米级液析,w[Ti]较高(70%~83%)的多呈多边形块状,w[Nb]较高(70%~85%)的多呈薄膜状或不规则块状,液析中基本不含V元素;Ti和Nb的碳氮化物液析可互溶并共同生长,Nb含量较高的液析以Ti含量较高的液析为核心长大为块状,部分液析以含硫夹杂物为核心形核并长大;连铸坯心部的碳氮化物液析较多,并且尺寸较大(最长达35μm),连铸坯表面的数量较少,尺寸较小(10μm以下);连铸坯经1 200℃加热并轧制后,液析可部分回溶,数量减少,尺寸减小,并且在轧制过程中破碎。

Metadynamic Recrystallization of the As-cast 42CrMo Steel after Normalizing and Tempering during Hot Compression

The existing researches of hot ring rolling process are mainly based on forged billet. Compared with the existing process, the new ring casting-rolling compound forming process has significant advantages in saving materials and energy, reducing emission and reducing the production cost. The microstructure evolution of the casting materials during hot deformation is the basis of the research of the new process. However, the researches on the casting materials are rare. The metadynamic recrystallization of the as-cast 42CrMo steel after normalizing and tempering during the hot compression is investigated. The tests are performed on the Gleeble-1500 thermal-mechanical simulator. The influence rule of the deformation parameters on the metadynamic recrystallization is obtained by analyzing the experimental data. The kinetic model of the rnetadynamic recrystallization is deduced. The analysis results show that the metadynamic recrystallization fraction increases with the increase of the deformation temperature and the strain rate. The metallographic experiments are used to investigate the influence rule of the deformation parameters on the grain size of the metadynamic recrystallization. The experimental results show that the grain of the metadynamic recrystallization could be refined with the increase of the strain rate and the decrease of the deformation temperature during hot compression. The occurrence of the metadynamic recrystallization during the hot deformation is more difficult in as-cast 42CrMo steel than in forged 42CrMo steel. The research can provide the foundation for the further research of the hot deformation behaviors of the as-cast structure and theoretical support for the new ring casting-rolling compound process.

Delayed Fracture Behavior of CrMo-Type High Strength Steel Containing Titanium

The delayed fracture behaviors of CrMo-type high strength steels containing different amount of titanium(0to 0.10%)were studied.The steels were quenched at 880℃ and tempered from 400℃ to 650℃,and a wide range of tensile strength was obtained.The sustained load tensile test was carried out by using notched tensile specimens in Walpole solution.The experimental results showed that with higher strength,the Ti-microalloyed steels show higher resistance to delayed fracture compared with non-microalloyed steel due to titanium beneficial role and microstructure changes.The undissolved TiC is uniformly distributed as strong hydrogen traps,retarding or preventing the diffusion and accumulation of hydrogen to lower-interaction energy sites,such as prior austenite and martensite lath boundaries in stress concentration area.Meanwhile,the grain refining effect of titanium is also an important factor to improve the delayed fracture resistance of Ti-microalloyed steels.The characteristics of delayed fracture remain nearly the same with titanium addition.

Effect of Mn on hardenability of 25CrMo axle steel by an improved end-quench test

With the sixth large-scale railway speed-up,the quality of the axles is essential to the safety of the locomotive.According to the high-speed axle technical standard for the control of alloy elements in axle steel,optimization experiments of 25CrMo steel composition were performed by vacuum inductive melting.In order to study the hardenability of high-speed rail axles,an improved end-quench test was put forward.The advantage is that it enables the heat to transfer along the axial direction,thus avoiding edge effects.The hardenability of 25CrMo axle steels with Mn content of 0.60wt.% and 0.80wt.% was investigated mainly by means of optical microscopy and hardness tests.The experimental results indicate that the Mn has a pronounced effect on the hardenability of the steel.With an increase in Mn content from 0.60wt.% and 0.80wt.%,the hardenability of 25CrMo axle steel increases and the hard microstructure is maintained at an increasing distance from the quenched end.From the surface of the water quenched end to the center of the sample,the microstructure is martensite,martensite with bainite,and bainite.

Phase change materials as quenching media for heat treatment of 42CrMo4 steels

In the present work,paraffin phase change material is used as quenchant for the heat treatment of 42CrMo4 alloy and compared with water,air,and CuO doped paraffin.The samples were prepared based on ASTM E 8M-98 standard for tensile test and then heated up to 830°C,kept for 4 h in an electric resistance furnace and then quenched in the mentioned media.Elastic modulus,yield strength,ultimate tensile strength,elongation,and modulus of toughness were determined according to the obtained stress?strain curves.Moreover,the hardness and microstructural evolution were investigated after the heat treatment at different media.The samples quenched in paraffin and CuO-doped paraffin are higher in ultimate tensile strength(1439 and 1306 MPa,respectively)than those quenched in water(1190 MPa)and air(1010 MPa).The highest hardness,with a value of HV 552,belonged to the sample quenched in CuO-doped paraffin.The microstructural studies revealed that the non-tempered steel had a ferrite/pearlite microstructure,while by quenching in water,paraffin and CuO-doped paraffin,ferrite/martensite microstructures were achieved.It is also observed that using the air as quenchant resulted in a three-phase bainite/martensite/ferrite microstructure.

Flow behaviour constitutive model of CuCrZr alloy and 35CrMo steel based on dynamic recrystallization softening effect under elevated temperature

In order to study the effect of dynamic recrystallization on the metal flow behavior during thermal deformation,the elevated temperature compression experiments of CuCrZr alloy and 35CrMo steel are carried out using Gleeble-3810 thermal simulator.It is proved that the samples underwent obvious dynamic recrystallization behavior during thermal deformation by microstructure observation of deformed specimens.The size of recrystallized grains increases as the temperature improved and the strain rate decreased.Meanwhile,the net softening rate caused by dynamic recrystallization is determined based on the stress-dislocation relationship.It can be found that the value of net softening rate increases quadratically as the Z parameter decreases,and the dynamic recrystallization net softening rate of CuCrZr alloy and 35CrMo steel are calculated to be 21.9%and 29.8%,respectively.Based on the dynamic recrystallization softening effect proposed,the novel elevated temperature flow constitutive models of two different alloys are proposed,and the related parameters are well defined and solved in detail.The predicted values of the obtained models are agreed well with the experimental values.

SIMULATED RESEARCH ON HOT FORMING MECHANISM OF 35CrMo STEEL

The significance of this paper lies in the application of bending-upsetting 35CrMo steel in train crack-shaft. The hot deforming tests of 35CrMo steel have been done on the Gleeble-1500 testing machine with the deformation temperature at the range of 900癈-1250癈, a strain strain of 0.05 s-1, 0.5 s-1, 1.0 s-1 and compress degree of 15%-80%. Through respectively analyzing and studying the microstructure of the specimen and getting the data from the testing, the results obtained are as follows: the model of flow stress and the stress-strain relationship of material hot deformation, the model of dynamic and static re-crystallization and the correlative references of hot forming parameters and changes of microstructure. The hot deforming stress-strain curses and relevantly re-crystallized micro-structure of 35CrMo steel are drawn at the deformation temperature of 1250 and the strain rate of 1.0 s. Through analyzing and regressive calculating the grain size of the deformation specimen of 35CrMo steel at different locations under the large-deformation and high-temperature conditions, the hot-deforming model of grain calculation is verified. The experimental results and the model of grain calculation can provide scientific basis for analyzing the hot deformation processes and controlling quality.

Combined Cellular Automaton Model for Dynamic Recrystallization Evolution of 42CrMo Cast Steel

The dynamic recrystallization(DRX) simulation performance largely depends on simulated grain topological struc?tures. However, currently solutions used di erent models for describing two?dimensional(2 D) and three?dimensional(3 D) grain size distributions. Therefore, it is necessary to develop a more universal simulation technique. A cellular automaton(CA) model combined with an optimized topology deformation technology is proposed to simulate the microstructural evolution of 42 CrMo cast steel during DRX. In order to obtain values of material constants adopted in the CA model, hot deformation characteristics of 42 CrMo cast steel are investigated by hot compression metal?lographic testing. The proposed CA model deviates in two important aspects from the regular CA model. First, an optimized grain topology deformation technology is utilized for studying the hot compression e ect on the topology of grain deformation. Second, the overlapping grain topological structures are optimized by using an independent component analysis method, and the influence of various thermomechanical parameters on the nucleation process, grain growth kinetics, and mean grain sizes observed during DRX are explored. Experimental study shows that the average relative root mean square error(RRMSE) of the mean grain diameter obtained by the regular CA model is equal to 0.173, while the magnitude calculated using the proposed optimized CA model is only 0.11. This paper pro?poses a novel combined CA model for simulating the microstructural evolution of 42 CrMo cast steel, which notably uses a ICA?based grain topology deformation method to optimize the overlapping grain topological structures in simulation.

15CrMo钢在稠油热采注蒸汽管道上的应用

与 2 0G钢相比 ,15CrMo钢具有较好的力学性能和可焊性 ,在 3 5 0～ 40 0℃也具有较高的持久强度和蠕变能力。用 15CrMo钢替换原用 2 0G钢管制作的稠油热采注蒸汽管道和炉管 ,其腐蚀速率低 ,使用寿命长 。

42CrMo钢大锻件去氢退火节能新工艺的研究

分析了氢在钢中的存在状态 ,以及氢的溶解度与扩散系数之间的关系 ,同时借助计算机科学地制定了4 2CrMo钢大锻件新的去氢退火工艺。新工艺大大缩短了锻件去氢退火的周期 ,通过生产实践表明 ,按新工艺退火的锻件质量合格 ,并且大幅度节约了能源 ,提高了生产效率。

钻杆接头材料35CrMo钢硫氮共渗层的摩擦学性能

为了提高钻杆接头的使用寿命,利用离子渗氮和硫氮共渗技术在钻杆接头材料35CrMo钢表面制备了氮化层和硫氮共渗层。在油润滑条件下采用自制的球-盘磨损试验机考察了表面渗层的摩擦磨损性能。利用了XRD研究了表面层的相结构,采用了带EDS的SEM对表面改性层和磨损表面进行了分析。结果表明:35CrMo钢硫氮共渗层的摩擦学性能明显优于原始渗氮层;具有优良润滑作用的FeS固体润滑膜在高硬度氮化层的支撑下,可以有效地改善钻杆接头的摩擦磨损性能。

35CrMo钢获得板条马氏体的热处理工艺研究

研究了 35Cr Mo钢获得板条马氏体的热处理工艺 ,并对其获得的板条马氏体组织进行了接触疲劳试验 ,结果发现板条马氏体的接触疲劳寿命为调质态的

CrMo钢热处理工艺对疲劳强度影响的研究进展

CrMo钢多用于高温及承载循环应力的环境中,为改善其力学性能,对热处理工艺进行改进。以不同用途CrMo钢为例,简述近年热处理工艺的改进方法。尤其是在承受循环应力的条件下,研究CrMo钢棘轮效应及蠕变行为的特征及热处理工艺对其的影响,为工程应用热处理工艺提供方法与思路。

改型CrMo钢螺栓材料热处理工艺研究

从力学性能、金相组织等方面对改型CrMo钢螺栓材料进行热处理工艺试验研究,确定了最佳的热处理工艺规范。通过对冲击断口和透射电镜显微组织分析,掌握了改型CrMo钢的强化和断裂机理,为在生产中使用该钢积累了充足的数据资料,填补了该钢国产化的数据空白,为该材料的进一步开发提供了可靠的理论依据。

Ni-P化学镀层对20CrMo钢腐蚀疲劳强度的影响

对比研究了不经热处理和经热处理的Ｎｉ－Ｐ化学镀层对抽油杆用２０ＣｒＭｏ钢的腐蚀疲劳强度的影响。结果表明，不经热处理的Ｎｉ－Ｐ化学镀层明显提高了钢基体的腐蚀疲劳强度，但却降低了基体的疲劳强度。经热处理后，腐蚀疲劳强度有所下降。Ｎｉ－Ｐ化学镀层中的磷含量的电子探针测量和镀层的Ｘ射线衍射分析结果表明，Ｎｉ－Ｐ化学镀层为非晶态结构。此外，还用扫描电镜观察分析了疲劳断口。

35CrMo钢热变形机制的模拟研究

以弯曲镦锻 3 5 Cr Mo钢火车曲轴为例 ,通过将该钢以 90 0℃～ 1 2 5 0℃变形温度 ;0 .0 5 s-1、0 .5s-1、1 .0 s-1的应变速率 ;在 Greeble-1 5 0 0试验机上进行压缩 1 5 %～ 80 %的热变形实验 ,和随后进行的微观组织分析得出了 :材料热变形屈服应力变化模型 ;材料热变形本构关系 ;动态与静态再结晶模型和热加工参数与微观组织变化的相关性资料。描绘了在 1 2 5 0℃ ,应变速率为 1 .0 s-1时 ,3 5 Cr Mo钢热变形应力应变曲线和相应的再结晶组织。通过对 3 5 Cr Mo钢在高温大变形条件下 ,试件内部各区域晶粒尺寸的回归计算 ,验证了该钢热变形晶粒计算模型。

扫描速度对42CrMo表面激光熔覆NiCrBSi熔覆层成形的影响

通过使用6 k W光纤激光器在42Cr Mo钢表面激光熔覆Ni Cr BSi合金涂层,研究了激光扫描速度对Ni Cr BSi熔覆层的宏观成形、显微组织和硬度的影响。采用金相显微镜、扫描电镜、显微硬度计等,对熔覆层的宏观尺寸、显微组织和硬度等进行了测试分析。结果表明,随着激光扫描速度的增加,熔覆层的熔宽、熔高、熔深和热影响区宽度都降低,熔覆层的稀释率稍有增加;熔覆层与基体为良好的冶金结合,熔覆层的组织随着扫描速度的增加得到细化,熔覆层的硬度先增加然后降低。

42CrMo钢回火方程的建立

通过回归分析给出了４２ＣｒＭｏ钢的回火硬度、回火温度及回火时间的函数关系式。该关系式具有精度高，使用方便。同时分析了回火参量Ｐ＝ｆ［Ｔ（Ｃ＋ｌｇτ）］的算法。

30CrMo大钢瓶破口分析

通过对 30CrMo大钢瓶破口的宏微观分析 ,认为该钢瓶发生破口分叉的原因是由于淬火温度偏高 ,加之回火不足 ,导致钢瓶在水压爆破试验时 。