冷轧980 MPa级马氏体钢产品研发

文章根据冷轧980 MPa级马氏体钢技术要求进行了化学成分和生产工艺设计,并采用中试平台开展了冷轧980 MPa级马氏体钢实验室退火工艺研究。研究结果表明,采用相同化学成分及轧制工艺生产的冷轧980 MPa级马氏体钢通过调整退火缓冷温度得到的产品屈服强度为750～940 MPa,抗拉强度达到1 020 MPa以上,延伸率在10%以上,满足技术要求。明确了缓冷温度对冷轧980 MPa级马氏体钢组织性能的影响规律,结合显微组织及成品机械性能确定该成分体系下均热温度为800℃、缓冷冷速为3℃/s、快冷冷速为45℃/s、快冷温度为280℃时,最佳缓冷温度为680℃。     

宝钢冷轧马氏体钢板的研发现状和应用

冷轧马氏体钢板属于超高强度的先进高强钢,有利于实现汽车结构件的减重。冷轧马氏体钢板按照抗拉强度分级,从最低980 MPa到最高1 700 MPa级别,通常用于汽车保险杠、车门防撞杆、门槛加强件等截面零件的制造,通常的成形方式为辊压。宝钢冷轧马氏体钢的研发开始于2006年,并在2009年开始商业化供货部分级别的产品。到2015年,宝钢已经商业化供货了980~1 400 MPa级的冷轧马氏体钢板,1 500 MPa级马氏体钢商业可供,并且工业试制成功了1 700 MPa冷轧马氏体钢板。依据宝钢冷轧马氏体钢板的产品和技术现状,对马氏体钢板产品的技术特点和应用进行了探讨,以期对马氏体钢板的研究和应用提供一些参考。     

退火工艺对超高强冷轧马氏体钢板力学性能的影响

以C-Mn-Si系冷轧马氏体钢为研究对象,分析了退火工艺对超高强马氏体钢强度和冷弯性能的影响。由于碳含量高,试验用钢淬透性良好,当水淬入口温度在710℃及以上时,都能获得极高的抗拉强度和稳定的马氏体组织。随过时效温度升高,马氏体钢抗拉强度降低、延伸率升高;而屈服强度和冷弯性能则先升后降,在180℃过时效时具有最高的屈服强度和最优的冷弯性能。经扫描电镜和显微硬度分析发现,过时效温度的变化会直接影响马氏体钢中的碳化物析出及粗化,当过时效温度大于200℃时,试验用钢碳化物开始粗化,降低了马氏体钢的宏观冷弯性能。     

莱钢Q345B热轧窄带钢质量控制

针对Q345B热轧窄带钢在使用中存在的冷弯裂纹、冷轧开裂等问题,对开裂部位取样进行大样电解及夹杂物能谱分析,结果表明,钢中存在较多大尺寸的夹杂物(149~1 003μm),主要组成为O、Si、Mn、S、Ca等,组织中出现了魏氏组织。通过改进生产工艺过程控制,采用低氧化性钢水控制技术,开发球缺型挡渣器,连铸机恒温度、恒拉速、恒液面控制工艺技术,优化中间包流场等措施,提高了夹杂物控制水平,Q345B带卷组织为F+P,组织均匀,晶粒度9级,满足用户使用要求。     

含硫易切削钢夹杂物控制试验研究

通过高温试验研究了钙处理和镁处理对含硫易切削钢中夹杂物的控制效果。钙处理后钢中夹杂物为CaAl-O+(Ca,Mn)S复合夹杂物、(Ca,Mn)S以及Mn S夹杂物;镁处理后钢中夹杂物为Mg Al2O4+(Mg,Mn)S、Al2O3+Mn S复合夹杂物、(Mg,Mn)S以及Mn S夹杂物。钙处理和镁处理后钢中的复合夹杂物所占比例分别为0.67%和3.57%。镁处理后钢中Ⅱ类Mn S夹杂物明显减少,91.7%的夹杂物尺寸小于3μm,纺锤率达到72.5%,其对夹杂物的控制效果优于钙处理。     

钙处理对无取向硅钢中非金属夹杂物的影响

采用电解法和扫描电镜研究了300 t转炉-RH精炼钙处理对无取向硅钢板(%: ≤0.005C、1.2～2.2Si、0.2～0.6Mn、≤0.20P、≤0.005S、0.2～0.6Al、0～0.01Ca)中夹杂物的影响。结果表明,钢中Al含量为0.25%和0.35%时,钢中溶解氧均小于1×10^-4%,钙处理后都会产生CaS夹杂物,尤其是含0.35%Al的钢水;钙处理可以有效减少钢中的夹杂物数量,尤其是0.5μm以下的微细夹杂物数量;钙处理后夹杂物的种类以AlN、CaS为主,同时还含有少量的氧化物夹杂物以及AlN-CaS复合夹杂物,尺寸主要为1.5～5.0μm。     

夹杂物对低合金钢点蚀诱发敏感性的影响

为了进一步提高低合金钢的抗点蚀性能,采用Ti/Al脱氧及Ca处理工艺熔炼并轧制制备了试验钢。利用场发射扫描电镜及能谱仪(SEM-EDS)、电化学极化试验及浸蚀前、后夹杂物的原位观测,研究了不同脱氧工艺钢中夹杂物在模拟海水介质中诱导点蚀的行为。结果表明:与Al脱氧钢相比,Ti脱氧钢中形成了富含Ti Ox、数量更多、尺寸更细小的夹杂物,有利于Mn S的局部分散析出,降低其诱发点蚀的危害,采用Ti脱氧工艺有助于提高钢的抗点蚀性能;Mn S诱发点蚀的能力强于氧化物夹杂,点蚀优先在Mn S夹杂与基体的界面处及夹杂物曲率半径小的区域萌生;降低夹杂物的腐蚀活性应该以调控夹杂物的组成为基础,其次优化夹杂物的形貌(球形化),在微米级范围内,夹杂物尺寸对点蚀诱发的影响最小。     

邯钢600MPa级冷轧双相钢的连退工艺

通过DIL805-A测定了C-Si-Mn系600MPa级冷轧双相钢的CCT曲线,并在Gleeble 3500上模拟了双相钢的冷轧连退工艺。得出以下结论：双相钢的连退均热温度控制在800～820℃,保温时间不小于2min,缓冷温度控制在650～700℃,快冷结束温度不高于330℃,冷速大于15℃/s。通过EBSD检测、透射电镜检测、力学性能检测,结果显示邯钢生产的C-Si-Mn成分体系600MPa级冷轧双相钢马氏体的体积分数约为18%,{111}面织构强度为5.3,双相钢中马氏体类型为低碳马氏体,通卷屈服强度为344～365MPa,抗拉强度为605～645MPa,伸长率为24.5%～27%。其性能完全能满足汽车厂冲压安全防撞件的要求。     

热轧16MnRE钢的RE/S值变化与机械性能的关系

本文指出,在钢中含硫量一定的情况下,随着 RE/S 值的提高,σ_b,σ_s 基本保持不变,而δ_5略有增加;钢中长条状 MnS 夹杂物逐渐减少,冷弯性能逐渐改善。当 RE/S<1时,长条状 MnS 夹杂物较多,冷弯不合;当 RE/S=1～2时,钢中仍有少量 MnS 夹杂,个别批次的冷弯仍不合格;当 RE/S≥3时,没有观察到 MnS 夹杂物,只有颗粒较小的复合稀土夹杂物,冷弯合格。最后指出,RE/S 值不宜过高,若 RE/S>7,钢中硬性稀土夹杂物数量增多,颗粒粗大,这样反而会恶化钢的塑性和韧性。     

S含量对18CrNiMo7-6齿轮钢中夹杂物和疲劳性能的影响

以w[S]为0.002%（低S含量）和0.022%（高S含量）的两种18CrNiMo7-6齿轮钢为研究对象,参照齿轮热处理工艺获得伪渗碳试样,并对其力学性能、显微组织、疲劳性能和夹杂物分布进行了分析表征。结果表明,两种齿轮钢的强度基本相当,而高S含量试验钢具有更好的塑性和低温冲击韧性,并且其疲劳极限、疲劳寿命均优于低S含量试验钢,疲强比由0.445提高到0.479。S含量显著影响钢中的夹杂物分布情况：低S含量试验钢中夹杂物以MnS-Oxide为主,数量较少,同时尺寸更大;而高S含量试验钢夹杂物以CaS-MnS-Oxide复合型夹杂物为主,数量提高1倍以上,但尺寸更为细小。高S含量试验钢采用Ca处理工艺对夹杂物进行改性,夹杂物尺寸明显细化,有利于钢的塑韧性提升,并改善疲劳性能。     

Structure and Mechanical Properties of High-Strength Structural Steels

The structure and the mechanical properties of the high-strength structural martensitic steels used in manufacturing the mechanism parts subjected to significant cyclic dynamical loads are considered. All the steels have a similar martensitic–bainite structure and a high stability of their mechanical properties. At the same time, their structures are found to contain secondary phases, which can degrade their functional properties. 03Kh11N10M2T maraging steel exhibits fairly high impact toughness for this class of steels despite a brittle character of fracture during bending impact tests.     

Shear Fracture of Advanced High Strength Steels

Failure experiments were carried out through a stretch-bending test system for advanced high strength steels, i.e. dual-phase （DP） steels and martensitic steels （MS）. The die radius in this system was designed from 1 to 15 mm to investigate the failure mode under different geometries. Two failure modes were observed during the ex- periments. As a result, critical relative radii （the ratio of inner bending radius R to sheet thickness t） for DP590 and DP780 steels were obtained. The stretch-bending tests of DP980 display some trends unlike DP590 and DP780 steels, and curve of DP980 in different thicknesses does not coincide well. High blank holder force exhibits more possibility of shear fracture tendency than low blank holder force. The unique character of high strength martensitic steel （1500MS） is that no shear fracture is found especially over small bending radius （R =2 mm） under the same experi- mental conditions. Microstructure analysis indicates that there are obviously elongated grains on shear fracture sur- face. It shows smaller diameter and shallower depth of the dimples than the necking failure.     

马氏体不锈钢成分、工艺和耐蚀性的进展

介绍了马氏体铬不锈钢、马氏体铬镍不锈钢和马氏体时效不锈钢的进展和发展动态,讨论了化学成分、热加工、热处理工艺对马氏体不锈钢组织和耐蚀性的影响。当前国内开发的新型马氏体不锈钢主要为符合给定服役条件的专用钢类。优化化学成分,提高钢的纯净度,通过热加工和热处理工艺控制钢的组织,进行表面处理是提高马氏体不锈钢耐蚀性的有效途径。     

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.     

淬火温度对不同铬含量的低碳马氏体不锈钢组织和性能的影响

摘要：为研究淬火温度对不同铬含量的马氏体不锈钢组织和性能的影响,采用高温共聚焦显微镜(CLSM)、光镜(OM)、扫描电镜(SEM)、万能拉伸机、显微硬度计等方法对材料组织和性能进行了测试及表征。随着淬火温度的升高,不锈钢淬火后的晶粒尺寸都变大,计算确定了13%Cr和14%Cr不锈钢的晶界迁移能分别为113.62和125.92J/mol。13%Cr不锈钢经过淬火后显微组织为板条马氏体,回火后的组织为回火马氏体。但是,14%Cr不锈钢在1200℃淬火后生成了板条马氏体和少量的高温铁素体,并且在回火后高温铁素体并未消失,会对后续性能产生影响。淬火温度对不锈钢的强度影响不大。不锈钢中的铬质量分数从13%增加至14%,马氏体不锈钢强度增加,但伸长率有所降低。马氏体不锈钢的硬度随淬火温度的升高而下降,这主要与晶粒尺寸有关。     

The effect of molybdenum on high-temperature properties of 9 pct Cr steels

Heat-resistant 9 Cr steels with 1, 2, and 3 pct Mo were tested for mechanical properties, weldability, and creep-rupture properties. The elevated-temperature and rupture strengths increase with increasing molybdenum content. While the 9 Cr-1 Mo steel is martensitic and is precipitation strengthened with carbides, the 9 Cr-2 Mo and 9 Cr-3 Mo steels receive added benefits from precipitation of Laves phase and solid-solution strengthening. The latter cause little decrease in ductility and impact resistance. The 9 Cr-2 Mo and 9 Cr-3 Mo steels are characterized by a duplex microstructure which aids weldability. Weld cracking tests show no need for preheating the latter steels, although the martensitic 9 Cr-1 Mo steel is known to be susceptible to weld cracking if not preheated. Both duplex-structure steels have good resistance to stress-relief cracking. Anisotropy of mechanical properties, due to the orientation of the duplex structure in the rolling direction, is less than that observed in the fully martensitic 9 Cr-1 Mo steel.     

Effect of Carbon Reduction on the Toughness of 9CrWVTaN Steels

Nitride-strengthened, reduced activation, martensitic steel is anticipated to have higher creep strength because of the remarkable thermal stability of nitrides. Two nitride-strengthened, reduced activation martensitic steels with different carbon contents were prepared to investigate the microstructure and mechanical property changes with decreasing carbon content. It has been found that both steels had the microstructure of full martensite with fine nitrides dispersed homogeneously in the matrix and displayed extremely high strength but poor toughness. Compared with the steel with low carbon content (0.005 pct in wt pct), the steel with high carbon content (0.012 pct in wt pct) had not only the higher strength but also the higher impact toughness and grain coarsening temperature, which was related to the carbon content. On the one hand, carbon reduction led to Ta-rich inclusions; on the other hand, the grain grew larger when normalized at high temperature because of the absence of Ta carbonitrides, which would decrease impact toughness. The complicated Al₂O₃ inclusions in the two steels have been revealed to be responsible for the initiated cleavage fracture by acting as the critical cracks.     

我国内燃机气阀钢系列化发展趋势

根据我国汽车工业的发展形势预测气阀钢的发展趋势，并阐述气阀钢系列化的重要性，描述了世界各国气阀钢的系列概况，探讨了我国气阀钢系列化发展趋势，包括马氏体气阀钢、奥氏体气阀钢、气阀合金、低俣金进气阀用钢４部分。重点是马氏体和氏体气阀钢的发展。     

Novel Development of an NbC-Containing Powder-Metallurgical Martensitic Steel with Outstanding Tribocorrosion Resistance

The development of NbC-containing martensitic stainless steels has made it possible to unite the properties of high corrosion resistance and wear resistance. If NbC is used as a hard phase instead of chromium carbide, the abrasive wear resistance of the steels is increased due to the greater hardness of NbC. The solubility of chromium in NbC is low. For this reason, chromium is fully available to form a passive surface layer to increase the corrosion resistance. In the steel melt, niobium leads to the formation of primary NbC, which grows very rapidly. Atomization of PM steels leads to the formation of coarse primary hard phases that clog the nozzle. Therefore, until now, steels with NbC as a hard phase are produced using the PM route with so-called diffusion alloying; however, this production route is very complex and expensive. Herein, a novel Nb-rich MC-containing wear- and corrosion-resistant steel that is produced using the usual PM route is presented. This steel consists of a martensitic matrix with evenly dispersed Nb-rich MC having a volume of 2.5%. Due to the high hardness (>750 HV30) in combination with high resistance to pitting corrosion, the steel exhibits outstanding tribocorrosion resistance in 0.9% NaCl solution.     

锰对高氮超级马氏体不锈钢组织与性能的影响

为了进一步提高超级马氏体不锈钢的强塑性能和优良耐腐蚀能力,在实验室条件下研发制备了氮质量分数为0.35％、锰质量分数分别为0.4％和2.0％的2种新型超级马氏体不锈钢试料,并采用淬火-配分的工艺对其进行处理;借助万能试验机、光学显微镜、扫描电镜、透射电镜和电子背散射衍射等方法对试验钢的微观组织和力学性能进行表征测试.研...