热机轧制对中碳冷镦钢组织和性能的影响

采用热机轧制（TMCP）工艺技术生产中碳冷镦钢SWRCH35K M,增加了线材组织中铁素体的比例,并使珠光体组织部分粒状化,降低了线材强度和硬度,提高了塑性,且冷镦时金属流动性好、冷作硬化率低。用户可用其直接制作内六角螺栓和法兰面螺栓,免去球化退火工艺,取得明显的经济效益和环境效益。     

形变量和冷却速度对SCM435冷镦钢形变诱导铁素体相变的影响

通过热模拟试验研究了两相区轧制,研究了形变量（15%~40%）和冷却速度0.8 ℃/s和1.2 ℃/s对SCM435冷镦钢的形变诱导铁素体相变的影响。结果表明:SCM435钢在奥氏体和铁素体两相区（750~850 ℃）轧制,在0.8 ℃/s的冷速下,随形变量增加,形变诱导铁素体体积分数呈升高趋势,并存在粒状珠光体组织,硬度呈先降低再升高的趋势;在1.2 ℃/s的冷速下,随形变量增加,形变诱导铁素体体积分数呈降低趋势,并出现了粒状贝氏体组织,硬度呈升高趋势。     

显微组织对12Cr1MoV耐热钢力学性能的影响

采用控制轧制-弛豫-在线低温回火新工艺制备不同显微组织的12Cr1MoV试验钢,利用金相法、拉伸试验和冲击试验等方法研究显微组织对试验钢力学性能的影响。控制轧制-弛豫-在线低温回火工艺可制备符合GB/T 3077-1999性能要求的铁素体+珠光体型12Cr1MoV钢,其片层状珠光体含量、粒状碳化物的含量及分布是影响试验钢力学性能的主要因素,增加片层状珠光体含量,试验钢强度、硬度增加;细化铁素体晶粒、增加粒状碳化物明显提高试验钢的伸长率;分布在铁素体晶界的粒状碳化物含量增多,试验钢的冲击韧性明显降低。     

30t转炉-小方坯连铸生产ML40Cr冷镦钢盘条的实践

阐述了ML40Cr冷镦钢生产情况,对采用氧气顶吹转炉→LF钢包精炼炉→小方坯连铸→高速线材轧制生产的冷镦钢盘条进行了综合检验分析.结果表明,生产的10 mm盘条金相组织为铁素体+珠光体,晶粒度9 ～10级;钢中A、B、D类非金属夹杂物的级别分别为0.5级、1.0～1.5级和1.5～2.0级,单位面积内当量直径5μm的夹...     

铁素体轧制在传统热轧中宽带上的开发应用

阐述了唐山建龙利用传统中宽带生产线进行低碳钢铁素体轧制的过程,并对产品进行力学性能、金相和组织结构分析.结果表明,铁素体轧制组织为铁素体＋少量珠光体＋三次渗碳体,相对于奥氏体轧制,铁素体轧制屈服强度降低28％,抗拉降低13％,延伸率降低23％,冷轧屈服降低23％,抗拉降低12％,延伸率增加2％,n值增加7％,冷轧轧制力平均减小一半,r值降低25％,并对r值降低的原因进行了分析.经过客户多次实际应用,铁素体轧制实际应用效果良好.     

SCM435合金冷镦钢盘条控轧控冷工艺

对150 mm×150 mm连铸坯轧制Φ12 mm SCM435合金冷镦钢(%:0.35C、0.98Cr、0.16Mo)盘条的工艺试验表明:采用1020℃加热,900℃轧制,吐丝温度控制在780～800℃,相变前冷却速度控制在1℃/s左右,该钢可以获得均匀的铁素体+珠光体组织和良好的冷镦性能。     

高强度非调质冷镦钢研究和开发现状

根据国内外高强度非调质冷镦钢的研究和开发现状,分析和讨论了800～1 200 MPa高强度非调质冷镦钢的化学成分、工艺特点、组织和力学性能。高强度非调质冷镦钢应具有高的强度和有良好的冷成形性,其热轧材的强度和硬度应控制在一个合适的范围内。采用低碳高锰及微合金化的成分系列,通过热机轧制工艺,该钢种能获得良好的组织和力学性能。     

TMCP工艺对低碳Ni-Nb钢组织转变和力学性能的影响

 为了研究TMCP工艺对低碳Ni-Nb钢显微组织转变类型和晶粒尺寸的影响规律，研究了不同TMCP工艺下的显微组织特征及其对力学性能的作用机理。结果表明，在未变形轧制情况下，当冷却速度小于5 ℃/s时，显微组织为铁素体和珠光体，铁素体晶粒尺寸随着冷却速度的增大而减小；在变形轧制情况下，随着冷却速度的增加，组织中的铁素体晶粒尺寸明显减小；当冷却速度增大到5 ℃/s时，微观组织中出现了大量粒状贝氏体。试制钢板试验表明，当冷却速度为4 ℃/s时，试验钢的组织为准多边形铁素体，可以有效提高钢的低温韧性；当冷却速度达到6 ℃/s时，试验钢微观组织中出现大量粒状贝氏体，明显降低钢的低温韧性。     

高钒铸铁的组织、机械性能和耐磨性

制备了1．38％C-4．16％C和5．25％V～15．50％V的系列合金,X射线衍射检测表明,合金存在3种相,即铁素体,合金渗碳体和VC。碳化物。检测了共晶结构（共晶线）下C与V含量之间的关系,以及S。的共晶溶解度,除共晶结构外,高V铸铁基体组成如下：合金铁素体,粒状珠光体和层状珠光体,也有合金渗碳体＋粒状珠光体,粒状珠光体＋层状珠光体的混合组织,结果表明,从铁素体基体到粒状珠光体再到层状珠光体基体,硬度HB,抗拉强度Rm,屈服强度R0.2都增大,而伸长率如下降。磨损试验用2种方式,“试样一砂纸磨损”试验（P1）,“试样一对比试样磨损”试验（P2）。P1试验得出的结果为,（a）铁素体基体合金的硬度最低（182—189HB）,耐磨性最低（S=3．14～3．93mg／m）,（b）珠光体基体硬度范围为387—416HB,耐磨性与高锰钢相当（约S=2mg／m）,（C）层状珠光体＋粒状珠光体基体,硬度在322—401HB,有最高的耐磨性,S=0．24—0．62mg／m。总的来说,试验P2表现的耐磨性比P1高。     

400MPa级热轧带肋钢筋控轧控冷工艺应用试验

通过制定合理工艺参数,在生产线上对20MnSi连铸方坯进行了控轧控冷试验。试验结果表明,钢筋表层为回火索氏体+少量铁素体,过渡层为回火索氏体+珠光体+铁素体,半径1/2处为细小的珠光体+铁素体,晶粒度9.5级。轧制速度对控冷效果的影响最为明显,自回火温度对钢筋的组织和性能影响较大。     

Deformation induced pearlite transformation and dynamic spheroidization in a eutectoid steel

The microstructure evolution of a eutectoid steel during the deformation induced pearlite transformation of undercooled austenite was investigated by uniaxial hot compression simulation experiment. The effects of different deformation degree, deformation rates and deformation temperature on the deformation induced pearlite transformation were explored. The results indicate that the induced pearlite transformation can occur rapidly during the deformation, for the stress accelerates phase transition. With the increase of the deformation degree, the dislocation density and phase transition driving force in the microstructure are improved, accelerating the occurrence of phase transition and the process of cementite spheroidization. For the diffusion- controlled phase transition, the deformation rates decrease to prolong the deformation time, so the carbon atoms can diffuse sufficiently to obtain spheroidized cementite. At lower deformation temperature from A1 to Ar1, significant refinement of the fragmentation of cementite occurs due to the increase of supercooling and spheroidized time. The ultrafine microstructure of cementite particles can be obtained through the high deformation degree, low deformation rates and low deformation temperature. It is also observed that the pro- eutectoid ferrite nucleates along the austenite boundary in the process of deformation.     

Improvement of mechanical properties of pearlitic and pearlitic-ferritic steels by deformation-induced changes of microstructure

By using laboratory simulation tests thermomechanical processing, based on a post-transformation hot deformation with accelerated cooling, was employed on two steels with 0.46 and 0.76% C. Finer pearlite interlamellar spacing, reduced proeutectoid ferrite, and partially spheroidized pearlite bring about a substantial increase of strength without loss of toughness and ductility.     

16MnCr5钢形变热处理相变和显微组织研究

在热模拟机上测试了16MnCr5钢经1200℃加热的未变形奥氏体、在860℃经50％压缩变形奥氏体的CCT曲线和维氏硬度,研究了其相变组织。结果表明：未变形奥氏体以0.025℃/s连续冷却时和在860℃变形的未再结晶奥氏体以0．2℃／s连续冷却时及1100℃变形的再结晶奥氏体分别以0．05℃／s连续冷却和快冷至660℃等温退火时均得到多边形铁素体＋环光体组织。     

Microstructure deformation mechanism of SEM in- situ tension in high- strength anti- seismic rebars

To study the effect of different tissues on the performance of high- strength anti- seismic rebars, the law of its microstructure deformation behavior was obtained. The microstructures of three kinds of 500MPa high- strength anti- seismic rebars with different structural features were analyzed, which is mainly pearlite and ferrite, pearlite, ferrite and a small amount of bainite, as well as pearlite, ferrite and a large amount of bainite, respectively. The in- situ tension tests were used to investigate and study the polyphase microstructure deformation, polyphase microstructure coordination deformation mechanism and fracture mechanism. The results indicate that the ferrite and pearlite are deformed obviously in the test steels mainly with ferrite and pearlite. The ferrite is firstly deformed, however, the reason for unobvious deformation in pearlite may be attributed to the hindered effect caused by hard phase bainite. As the amount of deformation increases, the pearlite breaks finally. In the test steels which mainly composed of ferrite, pearlite and a small amount of bainite, the bainite does not substantially deform at the initial stage, while it impedes the deformation of ferrite and pearlite with only a certain degree of deformation. In the test steels which mainly composed of ferrite, a small amount of pearlite and a large amount of bainite, the initial deformation mainly begins in ferrite deformation, while the pearlite deformation is not obvious because of its low content. With the increase in deformation, the deformation of bainite becomes more and more obvious. When it reaches a certain extent, pearlite begins to deform and finally gets fracture.     

The effect of prior heat treatments on the structure and properties of warm-rolled AlSl 52100 steel

Isothermal rolling of AISI 52100 steel at 923 K (650 °C) has been used to produce very fine spheroidized carbide particles 0.1 to 0.2 μm in size in a submicron grain size ferrite matrix. Pearlitic starting structures are not completely spheroidized by such warm rolling and some isolated pearlite colonies remain after rolling. Tempered martensitic starting structures result in more uniform structures after rolling. The effect of varying the austenitizing time and temperature and of two cycle austenitizing treatments before rolling of tempered martensite were studied. After rolling, the room temperature yield strength was raised, a result of the finer dispersion of carbides and the associated reduction in ferrite grain size. The presence of isolated pearlite colonies in rolled material reduces the room temperature ductility. Formerly Graduate Student, Department of Mechanical Engineering, United States Naval Postgraduate School     

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.     

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.     

含有上贝氏体的ER8车轮钢的裂纹扩展行为

研究不同含量的上贝氏体对ER8车轮钢裂纹扩展行为的影响。利用激光共聚焦显微镜（LSCM）和扫描电镜（SEM）对ER8车轮钢的显微组织和裂纹扩展路径进行了研究。实验结果表明:ER8车轮钢中的组织除了有铁素体和珠光体,还存在上贝氏体;裂纹穿过上贝氏体和珠光体扩展,最终停止在珠光体区域;与珠光体组织相比,裂纹在上贝氏体中的扩展路径更曲折。利用扫描电镜（SEM）对ER8车轮钢的裂纹扩展变形进行原位观察。实验结果表明:含有80%上贝氏体的ER8车轮钢拉伸时,组织变形过程主要以铁素体和上贝氏体为主,裂纹在上贝氏体和珠光体中连续扩展,伴随着珠光体的变形;而含有50%上贝氏体的ER8车轮钢拉伸时,组织变形过程主要以铁素体和珠光体为主,并且上贝氏体对铁素体和珠光体的变形起到阻碍作用。上贝氏体能够有效地阻止裂纹扩展,在偏转裂纹路径和延缓裂纹扩展方面起着重要作用;并且对铁素体和珠光体的变形起到阻碍作用。      

PD3钢轨钢接触疲劳变形组织的TEM观察

在透射电镜下观察接触疲劳失效后不同状态的ＰＤ３钢轨钢的变形组织。结果表明，接触疲劳变形组织的主要特点是：珠光体片层间距减小，珠光体团被剪切分割成亚团，先析铁素体内形成位错胞结构；铁素体／渗碳体界面上存在高的位错密度；珠光体中渗碳体片发生变形与断裂。同时对珠光体片层间距与变形组织的关系进行了分析讨论。     

Effect of process parameters on microstructure and hardness of 49MnVS3 steel for automobiles

The thermal compression test of 49MnVS3 steel cylinder specimen was carried out using a Gleeble- 3500 thermal simulation testing machine, and the influence of deformation temperature, deformation degree and cooling rate on microstructure and hardness of 49MnVS3 steel was studied. The results show that the microstructure of 49MnVS3 steel at various deformation temperatures is composed of ferrite and pearlite. The pearlite is obviously homogeneous with 30% deformation than with 20% and 50% deformations, and the distribution of ferrite is more uniform. Under the conditions of deformation temperature of 850??, deformation degree of 30% and cooling rate of 10??/s, the microstructure is uniform, with less ferrite and more pearlite, and the refinement is obvious. However, as the cooling rate increases to 20??/s, martensite microstructure occurs, which affects the performance of the steel.