Cr4Mo4V钢热处理工艺对残余奥氏体量的影响

经对Cr4Mo4V钢进行热处理工艺试验，分析工艺参数对残余奥氏体量的影响，优化了热处理工艺参数，使Cr4Mo4V钢残余奥氏体量控制在5％以内，保证了热处理质量及尺寸稳定性。     

渗碳钢轴承残余奥氏体含量的控制

采取不同的工艺试验总结出有效的热处理工艺,将一批出口渗碳钢轴承残余奥氏体含量控制在15%～25%范围内,并保证了残余奥氏体含量控制的稳定性和重现性.     

ZGCr15钢制高温轴承尺寸稳定性

本文主旨在于研究残余奥氏体、马氏体和残余应力三者在高温轴承零件加工过程中的变化情况和对尺寸变化的影响。用六种不同的热处理工艺进行试验和分析对比。试件采用ZGCr15钢制的32118轴承套图和滚动体。实践证明:1.现行工艺采用三小时的回火时间是能够要求的。2.经225℃三小时回火在170℃温度条件下工作的轴承,由于残余奥氏体量较少,残余应力较小,因此具有较好的尺寸稳定性。3.经250℃回火三小时 在200℃条件下工作的轴承,残余奥氏体接近于零,残余应力也较小。在200℃时效过程中主要是马氏体脱溶起作用,使尺寸有所缩小。总的看来,它具有很好的尺寸稳定性。     

高速超精密轴承尺寸稳定性与疲劳寿命试验

对7205C/P4轴承的尺寸稳定性进行了工艺试验分析,并就不同的热处理工艺后残余奥氏体含量对尺寸稳定性及接触疲劳寿命的影响进行试验研究,提出了GCr15钢制超精密轴承残余奥氏体的控制量。     

冷处理对Cr12MoV钢硬度的影响

通过测定不同热处理条件下Ｃｒ１２ＭｏＶ钢的硬度值和残余奥氏体量,并通过金相和透射电观察发现,钢中的残余奥氏体和下贝氏体组织对冷作模具钢的耐磨性能有不利的影响,采用冷处理工艺抑制下贝氏体转变,显著提高Ｃｒ１２ＭｏＶ钢的硬度和耐磨性能。     

800MPa级冷轧相变诱发塑性钢的组织与性能

采用全自动热模拟试验机测定了新开发的800 MPa级相变诱发塑性钢的CCT曲线,据此制定了12种工艺对试验钢进行退火处理;通过拉伸试验测定了经不同工艺退火处理试验钢的力学性能,确定出了最优热处理工艺;对经最优工艺退火处理钢的显微组织和残余奥氏体的稳定性进行了研究。结果表明:各种工艺处理钢均获得了800 MPa以上的抗拉强度,获得最佳综合力学性能(强塑积最大)的热处理工艺为830℃退火120 s后,先以20℃.s-1的速率缓冷至700℃,再以40℃.s-1的速率冷至400℃,并在400℃等温处理400 s,最后以20℃.s-1的速率冷至室温;经最优工艺退火处理后钢的显微组织为50%铁素体+38%贝氏体+12%残余奥氏体,残余奥氏体主要分布在铁素体晶界处,或铁素体与贝氏体的晶界处,还有小部分存在于大的铁素体晶粒内;在拉伸过程中试验钢中残余奥氏体的相变大部分发生变形量为10%~20%阶段。     

冷处理对Cr12MoV钢硬度的影响

通过测定不同热处理条件下Cr12MoV钢的硬度值和残余奥氏体量,并通过金相和透射电镜观察发现．钢中的列余奥氏体和下贝氏体组织对冷作模具钢的耐磨性能有不利的影响．采用冷处理工艺可以抑制下贝氏体转变．显著提高Cr12MoV钢的硬度和耐磨性能．     

残余奥氏体对2.25Cr-1Mo钢焊缝冲击性能的影响

比较2.25Cr-1Mo钢埋弧焊焊缝经过720℃保温2 h(工艺1)以及680℃保温12h(工艺2)的冲击性能,结果表明热处理工艺1具有更好的冲击韧度;进一步测试工艺1接头液氮处理后的冲击性能,发现冲击韧度降低,推测残余奥氏体质量分数是造成这不同热处理工艺冲击性能差异的因素.采用振动样品磁强计和电子背散射衍射技术分别研究两种热处理试样的磁极化强度和相分布,获得了两种热处理工艺处理后焊缝金属的残余奥氏体质量分数,磁法测量表明焊后经工艺1处理后存在约3％左右的残余奥氏体,而经工艺2处理后残余奥氏体为0.2％; EBSD分析结果:工艺1的残余奥氏体质量分数为3.49％,工艺2的质量分数为0.18％,证实了焊缝中残余奥氏体质量分数的变化对冲击性能具有一定的影响.     

热处理工艺对Cr4Mo4V钢显微组织及断裂韧性的影响北大核心

采用不同热处理工艺对Cr4Mo4V钢进行处理,观察了其显微组织,测定了残余奥氏体含量,并进行了断裂韧性(KIC)测试,结果表明:淬火温度越高,马氏体越粗大;残余奥氏体越少,钢的尺寸稳定性越高,KIC值越小。     

热处理工艺对Cr4Mo4V钢显微组织及断裂韧性的影响

采用不同热处理工艺对Cr4Mo4V钢进行处理,观察了其显微组织,测定了残余奥氏体含量,并进行了断裂韧性(KIC)测试,结果表明:淬火温度越高,马氏体越粗大;残余奥氏体越少,钢的尺寸稳定性越高,KIC值越小。     

Magnetic properties and hardness of maraging steel 08X15H5Д2T and nondestructive testing of retained austenite in parts

Dependences of the coercive force, saturation magnetization, residual induction, relaxation magnetization and magnetic susceptibility, maximum magnetic permeability and associated magnetic field, electrical resistivity, and hardness of maraging steel 08X15H5Д2T on the conditions of preliminary heat treatments, hardening, and subsequent aging have been studied. The content of rtained austenite in specially prepared specimens was determined. These specimens were subsequently used to calibrate a differential magnetic instrument. Such an instrument is also used to determine the content of retained austenite in aircraft bolts.     

Q&P钢的显微组织及力学性能

采用盐浴炉对硅-锰系Q&P(quenching and partitioning)钢进行了Q&P工艺处理,研究了分配时间对热处理后试验钢显微组织、力学性能、残余奥氏体含量及残余奥氏体中碳含量的影响。结果表明:试验钢的显微组织为板条马氏体和残余奥氏体,残余奥氏体以两种形态分布在不同位置,一种是以薄膜状分布在马氏体板条间,另一种是以块状分布在原奥氏体晶界处;在300℃的分配温度下进行较长时间保温能取得较好的强塑积,随着分配时间的延长,试验Q&P钢的残余奥氏体含量及残余奥氏体中的碳含量均不断增加,分配时间为1 200 s时所得试验钢的强塑积最高,可达37 300 MPa.%以上。     

Residual stresses and retained austenite evolution in SAE 52100 steel under non-ideal rolling contact loading

Residual stresses are introduced and modified during manufacturing as well as by normal use under rolling contact loading. Operations such as heat treatments, shot peening, grinding, etc., are known to alter the magnitude and distribution of residual stresses. Our work revolves around the changes in magnitude and distribution of residual stresses, as they relate to deformation and the strain induced transformation of retained austenite. The residual stresses and retained austenite measurements were carried out using X-ray diffraction techniques. The rolling contact fatigue lives of different variants of SAE 52100 bearing steel were evaluated in a 5-ball-rod rolling contact fatigue machine under testing conditions leading to surface nucleated failure, i.e. non-ideal rolling contact. The tests were accelerated by applying well controlled micro-indentations on the wear track. The contribution of the residual stresses and amount of retained austenite to the rolling contact fatigue life were analyzed.     

两相区退火对相变诱发塑性钢显微组织与力学性能的影响

对低碳硅锰钢进行了水淬和随后的两相区退火与贝氏体区等温处理,利用光学显微镜、扫描电镜和透射电镜对热处理后试验钢的显微组织进行了观察,采用X射线衍射仪测定了钢中残余奥氏体含量,通过拉伸试验测试了钢的力学性能。结果表明:两相区退火冷却后试验钢的显微组织为铁素体与马氏体,随着两相区退火温度的升高和保温时间的延长,铁素体含量减少,马氏体含量增多,其中铁素体大部分为长条状;经贝氏体区等温处理后,显微组织中的残余奥氏体大部分以板条状存在于贝氏体板条界,极少量以块状存在于先共析铁素体内,其含量随着退火温度的升高和保温时间的延长先增加后降低,在780℃保温5 min时达到最大值;试验钢抗拉强度和屈服强度均随着退火温度升高和保温时间延长单调上升,伸长率在780℃等温5 min时达到最大值。     

Eddy-current and coercive-force testing of abrasion-resistant ball bearing steel IIIX15 subjected to laser and bulk thermal processing

The possibility of using the eddy-current and coercive-force methods for assessment of the structural state and the abrasion resistance of ball-bearing steel IIIX15 (1.00% C and 1.42% Cr) is studied. The steel was subjected to laser and bulk quenching, subzero treatment, and tempering in the temperature range 75–600°C. The presence of residual austenite (in an amount of up to 45 vol %) in the quenched structure is shown to affect the sensitivity of the coercive-force and eddy-current methods used to test the abrasion resistance of steels tempered at low temperatures. Variations in hardness, abrasion resistance, and the parameter of the electromagnetic eddy-current testing as a function of the depth of the laser-irradiated zones in steel IIIX15 subjected to preliminary thermal strengthening is considered.     

Effect of retained austenite on rolling element fatigue and its mechanism

Experiments were carried out on a rolling contact fatigue testing machine with two rollers as specimens which were made of the commercial steel 18Cr2Ni4WA. Various treatments are conducted to obtain rollers with different amounts of retained austenite. The experimental results show that the contact fatigue resistance of the specimen with the largest amount of retained austenite is much better than that of the specimen with the smaller amount of retained austenite. It is considered that the precipitation particles from austenite, the deformation-induced martensite, the beneficial alteration of the residual stresses and the toughness of the austenite are the main reasons for the high contact fatigue resistance of this steel.     

A magnetic method for determining the concentration of residual austenite in maraging steels

The results of measurements of magnetic properties of maraging steel 08Kh15N5D2T subjected to different types of thermal treatment, namely annealing, hardening, and aging, are presented. The required concentration of residual austenite during specimen preparation was obtained by varying the temperature of thermal treatment, the time of exposure, and the heating rate in the case of annealing. The new magnetic parameter N*, which linearly correlates with the concentration of residual austenite, is proposed. An algorithm for previously developed equipment and software, which is intended for the determination of this parameter, is offered.     

热输入对1 000 MPa级工程机械用钢接头组织性能的影响

采用三种热输入进行1 000 MPa级控轧控冷(Thermo mechanical control process, TMCP)高强钢的熔化极气体保护焊,利用金相显微镜、扫描电子显微镜和透射电子显微镜研究热输入对焊接接头组织和力学性能的影响。研究结果表明,三种热输入焊缝金属组织主要由板条马氏体和板条贝氏体为主、并含有少量残余奥氏体和粒状贝氏体;焊接热影响区粗晶区组织以板条马氏体和贝氏体为主,并含有少量粒状贝氏体。随着热输入的增加,焊缝组织中贝氏体板条粗化,马氏体板条减少,而粒状贝氏体逐渐增多,部分膜状残余奥氏体向块状转变;焊缝金属冲击韧度和硬度、接头强度逐渐降低,而接头热影响区冲击韧度先增后降;当热输入为15 kJ/cm时焊接接头强韧性匹配最佳。     

Prolonging the service life of shot-blaster blades made from high chromium cast iron

By using chill technology in the sand mold and improved heat treatment technology, superior shot-blaster blades were made from high chromium cast iron near eutectic composition. When steel pellets are shot, the service life of this kind of blade was 670 h, about twice the 328 h of the GF blades (made in Switzerland). Under the condition of shooting white iron pellets, the service life of this kind of blade was 380 h, about 1.5 times the 245 h of the domestic high quality blades.It was shown by performing a worn surface analysis of discarded blades and by a trial run of pilot blades that the wear of blades when shooting steel pellets was mainly caused by spalling, and there was little microcutting. Decreasing the amount of retained austenite and improving the toughness of martensitic matrix increased the wear resistance of these blades effectively. The wear of blades was mainly caused by microcutting when shooting white iron pellets, but spalling also contributed to wear. Increasing the hardness and decreasing the amount of retained austenite were beneficial to wear resistance of these blades. Unidirectional carbide arrangement perpendicular to the wearing surface also improved wear resistance of both types of blades.