60kg级低屈强比耐火钢的试验研究

对一种低屈强比建筑用耐火钢进行试验研究,介绍了试验钢的化学成分、试验工艺、力学性能等,重点论述了合金元素、组织等对钢的屈强比、高温强度的影响。结果表明,该钢具有良好的综合机械性能,组织为铁素体基体加贝氏体第二相,因此获得低的屈强比。合金元素Cr、Mo、Nb等的加入有效地提高了钢的高温性能。     

60kg级低屈强比耐火钢的实验研究

对一种低屈强比建筑用耐火钢进行实验研究，介绍了实验钢的化学成分、实验工艺、力学性能等，重点论述了合金元素、组织等对钢的屈强比、高温强度的影响。结果表明，该钢具有良好的综合机械性能．组织为铁素体基体加贝氏体第二相．因此获得低的屈强比。合金元素Cr、Mo、Nb等的加入有效地提高了钢的高温性能。     

建筑用耐火钢的研究现状及发展趋势

耐火钢是建筑钢结构的首选绿色钢铁材料。国外钢铁生产企业通过不同的成分设计思路相继开发了不同级别的耐火钢,并已大量应用于高层建筑。国内也进行了研究开发,且性能达到与国外耐火钢相当的水平,但是应用业绩较少,其原因是传统耐火钢Mo含量高,合金成本远高于普通建筑用钢。耐火钢必须通过一定量的贝氏体以保证良好的高温性能,而贝氏体属中温转变组织,对轧制及冷却工艺要求高,是耐火钢开发的难点。开发低Mo含量的低成本、高强度、高韧性耐火钢,并逐渐取代普通建筑钢+耐火涂层,是现代建筑钢结构的发展趋势之一。     

Mo对耐火钢组织性能的影响

对三种含Mo耐火钢组织和性能进行了实验分析,发现合金元素Mo在耐火钢中的主要作用是通过提高贝氏体淬透性来满足钢的高温性能.从组织学角度看,降低合金中的Mo含量而增加其它提高贝氏体淬透性的元素也能够满足耐火钢成分设计要求.探讨了设计低Mo或无Mo耐火钢的可能性.     

建筑结构用新型抗震耐火钢Q420FRE的开发

新型耐火钢除了要求具有等同或优于普通建筑钢的室温力学性能和良好焊接性能,还需要保证耐火性能和良好抗震性能,并拥有比传统耐火钢成本更低的特点。南钢基于实验室试验的结果,设计了低Mo新型耐火钢的化学成分和轧制工艺,试制了不同厚度规格的Q420FRE耐火钢,其各项性能均优于标准对同级别耐火钢的要求。600℃高温强度达到室温强度的70%,280 MPa恒载荷下的耐火极限温度约为700℃,模拟二次火灾高温强度仍超过280 MPa,屈强比0.83,具有良好的耐火及抗震性能。     

60 kg级低屈强比耐火钢的实验研究

对低屈强比建筑用耐火钢进行了实验研究，介绍了实验钢的化学成分、实验工艺、力学性能等；重点论述了合金元素、组织等对钢的屈强比、高温强度的影响。结果表明，该钢具有良好的综合机械性能，组织为铁素体基体 贝氏体，因此获得低的屈强比。合金元素Cr、Mo、Nb等的加入有效地提高了钢的高温性能。     

Cr对460 MPa级抗震耐火建筑用钢性能影响

设计了两种不同Cr含量460 MPa级抗震耐火建筑用钢,并进行了室温和高温机械性能检测,0.4%Cr和0.8%Cr试验钢的性能均满足抗震钢屈强比≤0.83,并且耐火钢600℃保温3 h后屈服强度≥307 MPa的标准。JMatPro热力学软件对460 MPa级抗震耐火建筑用钢的析出相进行计算,采用光学显微镜和透射电子显微镜方法对钢中的析出相进行了分析。结果表明,试验钢随Cr含量的升高,室温抗拉强度升高,屈强比降低,具有更好的抗震性能。Cr的增加,减少了高温稳定性较差的析出相的析出,降低了析出相中Mo的含量,促使Mo更多地溶入基体中,从而提高了抗震钢的高温固溶强化作用和耐火性能。     

Mo对耐火钢高温屈服强度的影响

设计了一系列Mo质量分数从0.1%到0.8%的Fe-Mo-C三元模型钢.采用两种不同热处理工艺制度得到不同的组织,研究了Mo元素对耐火钢高温强度的两种强化形式:固溶强化和贝氏体相变强化.Mo可以显著提高耐火钢的高温强度,它在耐火钢中的主要高温强化机理是固溶强化.Mo质量分数不高于0.5%时,其高温固溶强化效果明显,每添加0.1%的Mo,600℃的屈服强度增量为13.71 MPa;但当Mo质量分数大于0.5%后,高温强度增幅逐渐减小.此外,贝氏体相变强化对耐火钢的高温强度也有重要影响.当贝氏体体积分数达到20%时,耐火钢的高温强度显著增加.      

Nb-V微合金化低钼型Q345耐火钢的开发

 为了推动耐火钢的市场应用,采用低碳、低钼(约0.2%)及铌、钒、钛的复合微合金化成分设计,成功开发出低成本Q345耐火钢。采用Formastor-Digital全自动相变测试仪测定了试验钢的连续冷却转变(CCT)曲线,利用Gleeble-1500热模拟试验机研究了变形后不同冷却工艺对试验钢组织及硬度的影响,并采用SEM、EBSD、TEM和物理化学相分析等手段对热轧及600 ℃高温拉伸试样基体组织及纳米第二相进行了详细表征,定量分析了试验钢室温及高温下的强度机制。结果表明,轧后760~780 ℃开始层流冷却、终冷温度为400~600 ℃,试验钢获得铁素体+贝氏体组织。经600 ℃高温拉伸后,试验钢中MC相的质量分数及处于18 nm以下的粒子质量百分比相对于热轧态试样分别提高了16.4%、9.8%,这些新析出的纳米级粒子在高温下起到了良好的沉淀强化作用,一定程度弥补了高温下因剪切模量下降和细晶强化失效导致的高温屈服强度的损失;固溶、沉淀强化为Q345耐火钢主要的高温强化方式。     

热处理工艺对20Cr1Mo1VTiB螺栓钢组织及性能的影响

为了优化20Cr1Mo1VTiB螺栓钢的热处理工艺,采用SEM、TEM和力学性能测试等手段,研究了热处理工艺对该钢组织及性能的影响。结果表明,20Cr1Mo1VTiB钢热处理态组织为贝氏体,主要强化相为VC与针状M3C相。随着淬火温度的提高,VC逐渐溶解,固溶强化作用增加,室温和高温强度上升、韧性下降。在较低温度下回火,贝氏体板条位错密度高、组织应力大,强度高、韧性差;提高回火温度,VC逐渐长大,基体逐渐发生回复,室温和高温强度降低,韧性显著升高。1 030℃淬火+720℃回火后,20Cr1Mo1VTiB钢体现出良好的强韧性匹配。     

高铝310S耐热钢板材的焊接性能简

 对铝含量为2%、4%(质量分数,下同)的310S耐热钢板材采用手工氩弧焊(TIG)的焊接方法进行焊接,利用光学显微镜对焊缝的显微组织进行分析,利用电子探针(EMPA)分析焊接母材的元素分布,并对焊接接头进行室温和高温(800℃)力学性能测试。结果表明：不同铝含量的310S耐热钢板材焊接后的组织均良好,都没有宏观裂纹及夹杂等缺陷;铝元素的加入,抑制了焊接热影响区晶粒的异常长大,细化了晶粒;高铝310S的焊接板材与母材一样具有优良的室温力学性能和高温力学性能,加铝310S耐热钢具有良好的焊接性能。     

Effect of Chromium on Microstructure and Mechanical Properties of Cold Rolled Hot-dip Galvanizing DP450 Steel

Two cold rolled hot-dip galvanizing dual phase(DP) 450 steels with different amounts of chromium were designed and the effects of the chromium concentration and galvanizing processes on the microstructure and mechanical properties were also investigated. The results show that the experimental steels exhibit typical dual phase microstructure character. However, the ferrite phase of steel with higher chromium is more regular and its boundaries are clearer. Meanwhile, martensite austenite(MA) island in steel No. 2 is diffused and no longer distributes along the grain boundary as net or chain shape. More MA islands enriched with Cr element can be found in the ferrite grains, and the increment of Cr element improves the stablity of the austenite so that the austenite has been reserved in MA islands. In addition, the experimental steel with higher chromium exhibits better elongation, lower yield ratio and better formability. The mean hole expanding ratio of steels No. 1 and No. 2 is 161.70% and 192.70%, respectively.     

Effect of Finish Rolling Temperature on Microstructure and Mechanical Properties of High Grade Pipeline Steel

The correlation among finish rolling temperature (FRT),microstructure and mechanical property of the high grade pipeline steel was investigated in this study.The microstructure of the steels with different finish rolling temperatures was observed with scanning electronic microscope (SEM) and transmission electronic microscope (TEM).The martensite/austenite (M/A) islands distribution was fixed by colour metallography,and the mechanical properties of the steels were tested with quasi-static tensile testing machine.The result shows that the fraction of M/A island increased with the finish rolling temperature decreasing,and when the finish rolling temperature is 800℃,the mechanical properties are the best.     

Effect of Heat Treatment Process on Mechanical Properties and Microstructure of Modified CNS-Ⅱ F/M Steel

 Ferritic/martensitic (F/M) steels have been recommended as one of the candidate materials for supercritical water cooled reactor (SCWR) in-core components use for its high thermal conductivity, low thermal expansion coefficient and inherently good dimensional stability under irradiation condition in comparison to austenitic steel. CNS-Ⅱ F/M steel which has good mechanical properties was one of the 9-12Cr F/M steels designed for SCWR in the previous work. In this study a modified CNS-Ⅱ F/M steel was used and it′s ultimate tensile strength was 925 MPa at room temperature and 483 MPa at 600 ℃ after optimizing heat treatment parameter. The ductile to brittle transition temperature of modified CNS-Ⅱ F/M steel is -55 ℃. Those are at the same level or even higher than that of CNS-Ⅱ and some commercial F/M steels nominated for SCWR in-core component use. The transmission electron microscope (TEM) results showed that the mechanical properties of the tempered martensite was closely related to the decomposition stage of the martensite.     

Fracture toughness of aisi M2 high-speed steel and corresponding matrix tool steel

The influence of microstructural variations on the fracture toughness of two tool steels with compositions 6 pct W-5 pct Mo-4 pct Cr-2 pct V-0.8 pct C (AISI M2 high-speed steel) and 2 pct W-2.75 pct Mo-4.5 pct Cr-1 pct V-0.5 pct C (VASCO-MA) was investigated. In the as-hardened condition, the M2 steel has a higher fracture toughness than the MA steel, although the latter steel is softer. In the tempered condition, MA is softer and has a higher fracture toughness than M2. When the hardening temperature is below 1095 °C (2000 °F), tempering of both steels causes embrittlement,i.e., a reduction of fracture toughness as well as hardness. The fracture toughness of both steels was enhanced by increasing the grain size. The steel samples with intercept grain size of 5 (average grain diameter of 30 microns) or coarser exhibit 2 to 3 MPa√m (2 to 3 ksi√in.) higher fracture toughness than samples with intercept grain size of 10 (average grain diameter of 15 microns) or finer. Tempering temperature has no effect on the fracture toughness of M2 and MA steels as long as the final tempered hardness of the steels is constant. Retained austenite has no influence on the fracture toughness of as-hardened MA steel, but a high content of retained austenite appears to raise the fracture toughness of as-hardened M2 steel. There is a temperature of austenitization for each tool steel at which the retained austenite content in the as-quenched samples is a maximum. The above described results were explained through changes in the microstructure and the fracture modes. CHONGMIN KIM, formerly with Climax Molybdenum Company of Michigan, Ann Arbor, MI.     

Structure and mechanical properties of Fe-Cr-Mo-C alloys with and without boron

A study of the structure and mechanical properties of Fe-Cr-Mo-C martensitic steels with and without boron addition has been carried out. Nonconventional heat treatments have subsequently been designed to improve the mechanical properties of these steels. Boron has been known to be a very potent element in increasing the hardenability of steel, but its effect on structure and mechanical properties of quenched and tempered martensitic steels has not been clear. The present results show that the as-quenched structures of both steels consist mainly of dislocated martensite. In the boron-free steel, there are more lath boundary retained austenite films. The boron-treated steel shows higher strengths at all tempering temperatures but with lower Charpy V-notch impact energies. Both steels show tempered martensite embrittlement when tempered at 350 °C for 1 h. The properties above 500 °C tempering are significantly different in the two steels. While the boron-free steel shows a continuous increase in toughness when tempered above 500 °C, the boron-treated steel suffers a second drop in toughness at 600 °C tempering. Transmission electron microscopy studies show that in the 600 °C tempered boron-treated steel large, more or less continuous cementite films are present at the lath boundaries, which are probably responsible for the embrittlement. The differences in mechanical properties at tempering temperatures above 500 °C are rationalized in terms of the effect of boron-vacancy interactions on the recovery and recrystallization behavior of these steels. Although boron seems to impair room temperature impact toughness at low strength levels, it does not affect this property at high strength levels. By simple nonconventinal heat treatments of the present alloys, martensitic steels may be produced with quite good strength-toughness properties which are much superior to those of existing commercial ultra-high strength steels. It is also shown that very good combinations of strength and toughness can be obtained with as-quenched martensitic steels.     

不同退火工艺下TWIP钢微观组织及力学性能演变

摘要：以在650℃温轧的Fe-24Mn-2Al-1Si-0.05C TWIP钢为研究对象,通过金相显微镜(OM)、扫描电镜（SEM）、透射电镜（TEM）、室温拉伸等实验手段,研究温轧TWIP钢在回复退火、部分再结晶退火、高温短时退火以及高温退火等不同退火工艺下其微观组织及力学性能的演变。结果表明,随着退火工艺的改变,实验钢的微观组织由回复退火时包含高密度位错、形变孪晶等的变形晶粒逐渐向高温退火时的无畸变再结晶晶粒转变;而部分再结晶退火时,实验钢的微观组织由未再结晶区的变形晶粒和细小的再结晶晶粒混合组成。随退火工艺的改变,实验钢拉伸前、后的硬度变化趋势为先下降然后基本不变最后上升;实验钢的变形机制逐渐由位错滑移为主向孪生滑移为主转变。     

Effect of Cooling Start Temperature on Microstructure and Mechanical Properties of X80 High Deformability Pipeline Steel

 The effect of cooling (laminar cooling) start temperature on the phase constitution was analyzed by quantitative metallography. The martensite/austenite (M/A) island distribution was fixed by colour metallography. The strength and uniform elongation of the steels were tested with quasi-static tensile testing machine. The in-coordinate deformation of the soft and hard phases was analyzed using FEM. The results indicate that when the cooling start temperature is 690 ℃, the mechanical properties are the best, meeting the requirements of X80 high deformability pipeline steel.     

Tensile deformation behavior of high strength anti-seismic steel with multi-phase microstructure

To investigate the tensile deformation behavior of high strength anti-seismic steel with multi-phase micro-structure, tensile tests with strains of 0.05, 0.12 and 0.22 were performed at room temperature.Micro-structure of tested steels was observed by means of optical microscopy (OM), transmission electron mi-croscopy (TEM) and scanning electron microscopy (SEM).Tensile mechanical properties of tested steels were obtained, and the influence of bainite content on deformation behavior was also discussed.Mean-while, the deformation mechanism of steel with three kinds of microstructures of bainite, pearlite and fer-rite was analyzed.Results show that tested steel with high volume fraction of bainite exhibits a continuous deformation behavior, and this may be attributed to a higher bainite volume fraction and a lower mobile dislocation density.The morphology of microstructure will influence the mechanical properties of tested steels.An increasing content of bainite can improve the tensile strength, but reduce the plasticity and toughness of the tested steels.In the deformation process of 0.039Nb steel, the ferrite and bainite have priorities to deform, and the deformation exhibits co-deformation of all microstructures in the later stage of deformation.In the deformation process of 0.024Nb-0.032V steel, the ferrite and pearlite have priori-ties to deform, and the deformation exhibits co-deformation of all microstructures in the later stage of de-formation.     

鞍钢1780机组汽车大梁板A420L、A510L的研制与开发

介绍了鞍钢1780机组新型含铌汽车大梁板（A420L、A510L）的生产工艺与组织性能。试验研究了A510L钢的高温塑性以及控冷控轧对钢组织和性能的影响,测定了汽车大梁板成形性参数。试验证明,鞍钢1780机组生产的汽车大梁板（A420L、A510L）具有良好的强韧性配合,优良的成形性能及较高的尺寸精度,可以满足汽车实际生产工艺的要求。