GCr15球化退火行为和力学性能的研究

采用等温球化退火和周期球化退火工艺分别研究了常规轧制（CR）和控轧控冷（TMCP）的GCr15钢的球化退火行为和力学性能。结果表明,轧制工艺对GCr15钢组织影响显著;在等温球化退火处理制度下常规轧制（CR）和控轧控冷（TMCP）试样球化效果差别较小;在周期球化退火处理制度下,控轧控冷（TMCP）试样可获得细小均匀的球化组织,其球化效果明显优于常规轧制（CR）试样,且球化退火时间比宝钢特钢现行的等温球化退火工艺缩短了6 h,可显著提高生产效率。     

20钢球化退火工艺研究

采用双相区和亚温区球化退火工艺研究20钢的球化退火行为和力学性能,结果表明,亚温区球化退火较双相区球化退火碳化物球化效果明显,力学性能良好,球化退火时间显著缩短。     

控冷工艺对冷镦钢SCM435组织及退火的影响

研究在不同控冷工艺下,合金冷镦钢SCM435相变过程中珠光体退化及退火效果.采用降低吐丝温度,提高斯太尔摩冷却线辊道速度,同时打开保温罩等工艺,得到均匀退化的理想珠光体组织,该组织在较短的退火时间下,得到均匀的球化组织,利于大变形量冷镦加工.探讨在控冷工艺下珠光体的退化,优化现有生产工艺.     

高碳铬轴承钢棒材轧后控冷工艺

阐述了轧后控冷工艺的机理,介绍了在特殊钢分公司连轧棒材线上运用轧后控冷技术,细化高碳铬轴承钢球化前的预备组织,获得片层间距较细的片状珠光体,在球化退火后,组织均匀细小,可获得细小弥散的碳化物颗粒,使网状碳化物级别≤2.5级,保证了产品质量。运用轧后控冷技术代替正火工艺,降低了生产成本。     

奥氏体化时间对GCr15轴承钢球化组织的影响

采用光学显微镜和扫描电子显微镜对GCrl5轴承钢热轧穿孔后、805℃奥氏体化不同时间后以及三种不同球化退火工艺后的组织进行研究.结果表明:组织中存在两种碳化物粒子,一种是比较大的先共析碳化物粒子,一种是小的碳化物粒子.随着805℃保温时间的延长,片层珠光体逐渐消失,小的碳化物粒子在数量上逐渐减少,在尺寸上逐渐变小,先共析碳化物粒子的大小和分布形态没有显著变化;三种球化退火工艺下,硬度相差不大.     

轴承钢GCr15棒材产品低温精轧的研究

采用国外引进的可实现低温精轧的生产线，对轴承钢GCr15棒材产品进行了低温精轧，通过低温精轧降低了网状碳化物级别，减少了球化退火时间。研究得到了低温精轧轧制GCr15时以控制网状碳化物级别为目标的轧制温度范围为750～840℃，轧后冷却温度范围为600～680℃，同时也研究得到了低温精轧轧制GCr15时以控制网状碳化物级别及减少球化退火时间为目标的轧制温度范围为750～800℃，轧后冷却温度范围为600～680℃。通过该研究网状碳化物级别达到了2级以下，球化退火时间由原18h减少到了11h。     

冷却速率和奥氏体化温度对40Cr钢球化退火的影响

为探究奥氏体化温度和冷却速率对40Cr钢球化过程的影响,采用双相区球化退火研究了热轧态40Cr钢的球化退火行为和力学性能.奥氏体化温度从760℃提高到800℃,冷却速率从10℃·h-1上升到30℃·h-1,组织硬度随冷却速度呈V形变化,碳化物球化率随冷却速度变化正好与前者相反.奥氏体化温度为760℃,冷却速率为20℃·h-1所得到的球化组织球化率高,且碳化物细小,具有良好的冷成形性能,可大幅度缩短球化退火时间,显著提高生产效率.提出了球化退火过程中离异共析转变机制,控制好球化过程中奥氏体化温度、冷却速率及保温时间有利于离异共析转变的发生.      

高纯净GCr15轴承钢组织演变与快速球化工艺的研究

利用碳化物的金相形貌、数量、大小、分布及圆整度表征试验钢的球化质量,通过不同的热处理制度研究高纯净GCr15轴承钢预备组织与退火工艺对碳化物球化质量的影响。试验表明:优良的预备组织适宜的退火制度有利于碳化物在短时间内球化和细化,采用文中退火制度a,GCr15轴承钢碳化物圆整度为0.087μm、平均粒径为0.27μm,球化时间比传统工艺减少3.5 h。     

Nb对高碳钢珠光体球化的影响

摘要：设计了2种不同Nb含量的高碳珠光体钢（0.025Nb和Free -Nb），采用光学显微镜、扫描显微镜、透射电镜和硬度测试仪对两种试验钢珠光体球化前后的显微组织进行了观察和球化后的硬度进行了测量。结果表明：Nb元素可以细化高碳珠光体钢的片层间距，相同条件下具有更多的铁素体 渗碳体界面，在球化退火的第一阶段提供大量的位错和亚晶界使片状珠光体快速熔断，同时也给第二阶段碳的扩散提供高速扩散通道；细小的片层间距缩短了碳和合金元素的扩散距离，使球化转变速度加快，促进了高碳珠光体的球化。Nb元素的添加获得了细小片层间距以及更多的合金碳化物使试验钢的初始硬度偏高，球化退火前4h硬度值下降幅度较大，球化退火4h后对试验钢硬度的影响不大。     

铬轴承钢控冷与快速球化退火工艺的最优化

本文分析了热轧铬轴承钢产品质量存在的问题,根据实验室和工业性实验的结果,研究了快冷开始的温度、速度和终了的温度,以及球化退火工艺对铬轴承钢组织和性能的影响。同时,在理论上论述了控冷与快速球化退火的最优化。     

高强度冷镦钢热机轧制工艺模拟试验研究

通过对35CrMo钢热模拟试验，研究高强度冷镦钢线材热机轧制工艺。试验表明，高强度冷镦钢经过热机轧制，可以避免形成马氏体和粒状贝氏体，提高铁素体含量12％～16％，因而材料被显著地软化。热机轧制可以促使珠光体直接球化；随热机轧制变形量增大，得到的铁素体晶粒越细，粒状珠光体的数量越多。     

Spheroidization cycles for medium carbon steels

An investigation has been made of spheroidization of medium carbon steels used in the bolt industry. Two process cycles were considered. One was the intercritical cycle, widely used in industry, in which the steel was heated above the lower critical, A1, temperature for approximately 2 hours; then cooled below it; and held for various periods to allow the austenite to transform and carbides to spheroidize. The other process was a subcritical cycle, which involved heating to below the A1 for various times. Wire samples of two steels were studied: AISI 1541, which is high in manganese and considered difficult to spheroidize, and AISI 4037, which is considered easier to spheroidize and is used extensively in industrial applications. Both cycles produced similar drops in hardness. However, 1 hour of the subcritical cycle yielded greater ductility than 32 hours of the intercritical process, as measured by tensile tests. Results of a new flare test designed to evaluate formability also indicated much faster spheroidization in the subcritical cycle. The level of spheroidization was defined in this study to be the percentage of carbide particles with aspect ratios less than 3. In 30 minutes, the subcritical cycle produced the same percentage of particles with an aspect ratio of less than 3 as produced by the intercritical cycle in 32 hours. The fast spheroidization in the subcritical process is attributed to the fine pearlite generated by the current practice of rapid cooling off the hot mill. This advantage is lost in the intercritical process as the original pearlite is dissolved above the A1 temperature.     

The Effect of Microstructure of Hot Rolled Alloy Steel Wire Rods on Cold Heading Annealing Process

Cold heading carbon steels for 8.8 grade fasteners are mostly produced by pouring reel or spooler plant.Currently,with improvement of cold heading equipment,the 10.9 grade fasteners produced by cold heading have replaced most of hot forged fasteners gradually.As well known,wire rod coil has been used to produce alloy steels.The properties and microstructures of medium carbon alloy steels,such as B7,ML40Cr and SCM435,produced by wire rod coils under hot rolled condition and after spheroidization,have been investigated.In this paper,the effect of microstructure of hot rolled steel wire rods on cold heading annealing process was studied.The results show that the hardness of wire rod coil products is generally lower than that of bar products by 5 ～ 10 HRB and the ferrite fraction in wire rod coil products is higher.After spheroidization treatment,the hardness value and spheroidization grade of wire rod coil products are relatively low.alloy steels of wire rod coils can be directly drawn slightly and the annealing time can be reduced at the same time.This practice is much helpful for energy conservation.     

Hot deformation-enhanced globularization of pearlite

A plain high-carbon steel (0.74% C) was used to study the globularization (spheroidization and coalescence) of pearlite. In order to induce and/or enhance this process, specimens were deformed in the temperature range of austenite-to-pearlite transformation. It was found that only hot deformation applied after the completion of pearlite transformation leads to spheroidization of pearlite. The rate of this process is accelerated by a factor of 10⁴ compared with annealing without deformation. The kinetics of pearlite spheroidization are dependent on the pearlite lamellae thickness as well as pearlite orientation with respect to the direction of deformation. The final microstructure is, compared with that after a conventional soft annealing, considerably finer, the strength properties thus being largely retained.     

CSP热轧50CrV4带钢普通球化退火工艺

系统研究了球化退火温度及保温时间对CSP热轧50CrV4带钢组织与性能的影响。研究结果表明:在730~770℃的温度范围内球化退火4~18h时,随着退火温度的提高,碳化物粒径先缓慢增大后迅速降低,球化率逐渐增大;随着保温时间的延长,碳化物粒径逐渐增大,730及750℃时,球化率先增大后降低;770℃时球化率逐渐降低。当退火温度为770℃,保温时间为4h时,球化效果最佳,球化率为90.6%,碳化物平均粒径为0.29μm,硬度为202.8HV。     

Ferrite recrystallization and austenite formation in cold-rolled intercritically annealed steel

The recrystallization of ferrite and austenite formation during intercritical annealing were studied in a 0.08C-1.45Mn-0.21Si steel by light and transmission electron microscopy. Normalized specimens were cold rolled 25 and 50 pct and annealed between 650 °C and 760 °C. Recrystallization of the 50 pct deformed ferrite was complete within 30 seconds at 760 °C. Austenite formation initiated concurrently with the ferrite recrystallization and continued beyond complete recrystallization of the ferrite matrix. The recrystallization of the deformed ferrite and the spheroidization of the cementite in the deformed pearlite strongly influence the formation and distribution of austenite produced by intercritical annealing. Austenite forms first at the grain boundaries of unrecrystallized and elongated ferrite grains and the spheroidized cementite colonies associated with ferrite grain boundaries. Spheroidized cementite particles dispersed within recrystallized ferrite grains by deformation and annealing phenomena were the sites for later austenite formation.     

临界区等温球化退火对低密度轴承钢组织和硬度的影响

摘要：临界区等温球化退火是实现高碳轴承钢中片状珠光体球化的主要热处理方式,其将片状珠光体转变为粒状珠光体,改善轴承件的可加工性及组织均匀性。研究了临界区等温球化退火工艺对低密度含Al轴承钢微观组织演化及硬度的影响。研究结果表明,轴承钢钢中高含量Al的添加可以提高临界区等温球化退火温度,缩短球化时间,将珠光体的硬度降低至300HV以下。但是,临界区等温球化保温过程中有石墨颗粒形成,石墨颗粒的产生虽然能够有效地降低球化后钢材硬度,但是部分石墨颗粒在最终的奥氏体化过程中难以溶解进入钢材基体,未溶解的石墨颗粒不仅增加了组织的不均匀性,而且降低了轴承钢硬度。所以,较长时间退火保温的临界区球化退火方式并不适用于低密度高碳高Al轴承钢。     

轴承钢珠光体球化的研究现状及发展趋势

概述了轴承钢球化退火在轴承生产中的作用,分析了珠光体由片层状转变为颗粒状的变化规律,讨论了片层渗碳体的打断、短棒状向颗粒状转变以及颗粒状熟化长大的热力学机制。结果认为珠光体球化工艺的不足,一是存在碳化物分布不均匀、尺寸大小存在差异等问题;二是退火工艺固定化、格式化等问题,未能适应轴承钢的发展;三是球化退火后的组织检验粗糙化、不够细致。球化工艺的发展趋势,一是要在轧钢或锻压生产阶段通过引入塑性变形或增大冷却过冷度等方法来保证片层组织更加均匀、细化,无网状渗碳体;二是要开发新的球化工艺,例如在有可能的条件内引入电场、磁场以及高温高压应力场等方法来改善球化工艺;三是要将球化组织的定量化检验标准化。     

70Nb合金钢丝双相区球化退火工艺

 采用正交试验法研究了大塑性变形70Nb合金钢丝双相区球化退火工艺。结果表明,在冷却速度一定(30 ℃/h)的条件下,决定球状碳化物尺寸的主要因素是保温时间(极差为0407,可信度达到67%)。最佳工艺参数为：加热温度770 ℃,加热时间60 min,保温温度680 ℃,保温时间360 min。其球状碳化物颗粒直径为181 μm,球化等级在35~40 级范围内,硬度HV 1681,较好的达到了锡林针布的使用标准。