微观组织对中碳微合金非调质钢疲劳性能的影响

用旋转弯曲疲劳试验研究了不同微观组织的中碳微合金非调质钢38MnVS的疲劳性能,并与调质处理的40Cr钢进行对比.结果表明,高温正火态38MnVS钢(38-N)具有粗大的贝氏体组织,疲劳性能最差;高温退火态(38-A)和热轧态(38-R)38MnVS钢具有粗大的网状铁素体,其疲劳性能亦较差;热锻态(38-F)具有细小均匀的微观组织和低的铁素体/珠光体硬度比,具有优于调质态40Cr钢的优异疲劳性能.因此,控制锻轧后微合金非调质钢38MnVS的微观组织可提高其疲劳性能.     

铁素体—珠光体型非调质钢及其控锻控冷技术

综述了国内外铁素体－珠光体型非调质钢发展现状，探讨了锻造温度、锻造变形量、变形速率及锻后冷却速度对非调质钢强韧化的影响，指出了旨在控制先共析铁素体组织参数和沉淀硬化效应的控锻控冷新技术。为稳定锻造用铁素体－珠光体型非调质钢性能，推动其规模化生产应用，开拓了前景。     

Nb-V复合非调质钢锻后组织变化

在Gleeble-3800热模拟试验机上进行热变形试验,研究Nb-V复合非调质钢在不同锻造工艺下的组织变化规律。结果表明,相对于单独添加V的非调质钢,Nb-V复合非调质钢锻后晶粒细小,铁素体含量增多,呈块状均匀分布,珠光体片层间距减小,且片层分布不规则,可改善钢的组织韧性。降低冷却速度有利于先共析铁素体长大,促使网状铁素体向块状铁素体转变,分布更均匀,有利于非调质钢韧性的改善。增大锻后变形量,可使组织细化。     

控锻控冷对非调质钢38MnVS5的组织影响

采用热模拟实验技术研究控锻控冷工艺对38MnVS5微合金非调质钢组织的影响。试验工艺参数包括变形量、热变形温度以及锻后冷却速率等,并观察晶粒和组织照片。结果表明,变形量为70％、终锻温度850℃的奥氏体晶粒细化最明显;锻后冷却速度越大,铁素体含量下降,铁素体尺寸越细小。     

氮含量对25Mn2CrVS贝氏体型非调质钢组织和性能的影响

研究了N含量(0.016wt%、0.029wt%和0.049wt%)对贝氏体型非调质钢25Mn2CrVS组织和力学性能的影响。结果表明:3组试验钢均为板条贝氏体、粒状贝氏体和铁素体组织,当氮含量从0.016%增加到0.029%时,试验钢强度和韧性增加,组织发生细化,且板条束状贝氏体含量减少,M/A相由长条状变成块状且分布弥散,针状铁素体增加;而氮含量增加至0.049%时,试验钢强度基本不变,韧性急剧下降,组织明显粗化,晶界铁素体形成。固溶钒可以促进板条束状贝氏体在晶界上的形成,奥氏体中析出的VN能够促进针状铁素体的形成。     

药芯焊丝焊缝中先共析铁素体的数量预测

合理控制低合金高强钢药芯焊缝金属中的先共析铁素体含量,对获得理想的焊缝性能具有重要意义。将焊缝凝固过程中的偏析效应引入基于扩散控制增长的先共析铁素体生长机制,指出成份偏析效应改变了先共析铁素体生长温度和时间区间,从而影响偏析微区内先共析铁素体的体积比例,建立了预测和分析药芯焊丝焊缝中先共析铁素体体积比例的模型,与实际试验结果有很好的吻合。     

磁场强度对Fe-0.76%C合金先共析铁素体显微组织的影响

借助于光学显微镜研究了磁场强度对Fe-0.76%C合金冷却转变过程的先共析铁素体显微组织的影响.结果表明:随着磁场强度的增强,该合金的先共析铁素体析出量和共析点的含碳量均明显增加.原因可归结为,强磁场使Fe-C合金的共析点向高温及高含碳量区域移动,使奥氏体向铁素体转变的初始温度升高.强磁场使先共析铁素体沿磁场方向伸长,而且随着磁场强度的增加,先共析铁素体的伸长方向与磁场方向之间夹角的平均值逐渐减小.上述现象可解释为:外加磁场使先共析铁素体晶核成为磁偶极子,并使其周围奥氏体原子作为磁偶极子更易于沿磁场方向向铁素体晶核扩散.     

大热输入焊接DH36钢焊接粗晶区组织与性能分析

利用焊接热模拟的方法,对比研究了大热输入焊接DH36钢焊接粗晶区的组织与性能.结果表明,低碳、低锰及低碳当量+微钛处理的合金设计可显著改善钢大热输入焊接粗晶区的组织与性能.随着t8/5的增大,大热输入焊接DH36钢粗晶区的组织由细小(尺寸1μm)的板条状马氏体-奥氏体岛(M-A岛)组织转变为大尺寸块状M-A岛组织,同时组织中先共析铁素体数量增多,尺寸增大.降低钢中的Mn元素含量可显著促进先共析铁素体的形成,抑制硬质相M-A岛的产生,但过多的粗大先共析铁素体形成会降低HAZ的低温韧性.M-A岛和先共析铁素体共同作用决定着大热输入HAZ的性能.     

低合金钢焊缝中先共析铁素体组织数量的控制

基于当量碳的概念，从扩散的角度出发，综合考虑了夹杂物粒子、合金元素和凝固偏析的影响，针对低合金钢焊缝组织中的先共析铁素体组织，建立了一个预测和模拟分析低合金钢焊缝中先共析铁素体组织的数量的数学模型。模拟结果表明，计算值与试验值吻合较好。     

汽车连杆用非调质钢及其控锻控冷技术

本文综述了国内外非调质钢发展现状以及其在汽车连杆上的应用，探讨了物理冶金因素和热加工因素对非调质钢强韧性的影响；指明了旨在控制先共析铁素体组织参数和沉淀硬化效应的控锻控冷新技术，为稳定汽车连杆用非调质钢性能，推动其规模化应用，开拓了新的前景。     

我国模具材料的发展概况及其选用

本文综述了冷作模具钢、热作模具钢、塑料模具钢三种常用模具用钢的发展与应用,特别对一些新型模具用钢的性能进行了介绍,并对今后模具钢的研发进行展望.     

Development of microalloyed high-carbon steels for plough disks

Plough disks are often made of high-carbon steels with small additions of chromium (0.40 to 0.60%), in the as-quenched and tempered condition. As a consequence, they combine wear resistance with the tensile, fatigue, and impact strength necessary to withstand extremely adverse work conditions. In an effort to produce steels for this use with improved mechanical properties, four different steel compositions, all microalloyed with niobium, were produced for the present work. Two steels kept the basic chromium content of the commercial alloy (0.40 to 0.60%), while this element was replaced with manganese in the other two steels. The chromium and manganese steels were produced with two levels of niobium. The Jominy hardenability, tensile properties, and impact and wear resistance of these materials were evaluated. A microstructural characterization was also performed. The results show that the developed steels can have the required hardness and strength levels. The high-niobium steels showed the best wear resistance but the poorest impact toughness. The wear resistance of the low-niobium steels was slightly higher and the impact toughness slightly lower than in the commercial alloy. The low-niobium steels show potential for commercial use.     

Effect of tempering on the toughness of a Cr- Mo bainitic steel

The effect of tempering on impact and fracture toughness properties of a Cr-Mo bainitic steel was studied in the quenched and stress relieved (Q & SR) condition. The lowest tempering parameter used resulted in considerable improvement in impact properties. Further tempering increased the upper shelf energy, had a minor effect on the transition temperature, and increased both the initiation fracture toughness (J_IC) and the tearing modulus(T). However, the effect on J_IC andT was much greater than the effect on the impact upper shelf energy. The results were discussed in light of the changes in microstructure and flow properties due to tempering.     

塑料模具材料的选用及发展概况

综述了塑料模具的工作条件、失效因素以及性能基本要求,主要介绍塑料模具钢和常用模具用钢的发展与应用,特别对某些新型模具用钢的性能进行了介绍,并对今后模具钢的研发进行展望.     

国内外模具用钢发展概况

我国模具工业近年来以每年15%左右的速度快速发展,2005年模具销售额610亿元,模具净进口总量为13.3亿美元.目前,我国的模具技术及模具寿命与一些工业发达国家相比,仍存在较大差距.正确的模具用材及其热处理在提高模具寿命中有重要作用.本文介绍了国内外冷作模具钢、热作模具钢和塑料模具钢的发展概况、最新进展及我国模具钢发展中存在的问题和对策.     

Magnetic properties of thin gauge 3% Si-Fe with {110}〈001〉 orientation

Thin-gauge 3% Si-Fe with {110}〈001〉 orientation is a suitable material for magnetic devices in the frequency range from 10² to 10⁵ Hz. Low core loss and high permeability in this frequency range are required. With recently developed, highly grain-oriented materials, physical parameters that affect core losses were investigated as a function of excitation frequency and magnetic flux density. The relationship between core loss and excitation conditions is classified into four regions. This material is useful for transformers and inductors, especially for higher flux density application in the middle frequency region (Bm[maximum excitation magnetic flux density] > 1T, 10² to 10³ Hz), such as airplane devices.     

耐候钢和碳钢大气腐蚀规律分析

对北京、青岛、江津、武汉地区的耐候钢与碳钢8年和16年的大气腐蚀数据进行方差分析,研究发现两类材料在北京地区的大气腐蚀数据无显著差异;在青岛、江津、武汉3个地区,虽然4年时耐候钢腐蚀速率明显低于碳钢,但8年和16年耐候钢与碳钢之间的腐蚀速率已无明显差异.     

Characterization of seven power-generating turbine rotors using microscopy-based techniques

Seven turbine generating rotors, either currently in service or recently retired, have been metallurgically examined using nondestructive techniques, including hardness testing and replication for optical and transmission electron microscopy. The aim has been to understand the microstructural changes occurring in a range of rotors due to service exposure. A decrease in hardness of up to 7% was noted, possibly arising from carbide-induced loss of molybdenum from solid solution. Optical microscopy was unable to detect service-induced microstructural changes. However, fine scale secondary precipitation of MC and M ₂ C were observed using transmission electron microscopy. A range of carbide compositional parameters associated with M ₃ C were found to vary with service exposure time.     

A review of microsegregation induced banding phenomena in steels

A review is presented of banding in hypoeutectoid and hypereutectoid steels. The data available on hypereutectoid steels are quite limited and therefore a study is presented on banding in a 52100 steel. Similarities and differences are identified in the banding that occurs in commercial hypoeutectoid versus hypereutectoid steels. The distinct surface patterns of Damascus steels, which are nearly pure hypereutectoid steels, have recently been shown to be due to carbide banding. It is shown that the carbide banding in the 52100 steel occurs by a distinctly different mechanism than the carbide banding of the Damascus composition steels.     

塑料模具材料的研制与应用

系统地综述了我国近年来塑料模具材料研制与应用的进展,介绍了一些新材料的牌号、化学成分、热处理、性能和用途,并对我国塑料模具材料今后的发展提出了一些建议,以便进一步推广应用。