含氮不锈钢氮气增氮的实验及工艺

通过采用氮气增氮的实验,研究了钢液的化学成分、冶炼温度、表面活性元素和吹氮流量对钢液增氮的影响.研究结果表明:钢中的合金元素尤其是Mn、Cr等元素能够增大钢液氮的溶解度;冶炼温度提高,钢液的增氮速率增大;钢中的氧对钢液的增氮有很大的阻碍;吹氮流量增大则钢液的增氮速率相应增大.同时对含氮不锈钢采用吹入氮气增氮工艺进行了探讨,为含氮不锈钢的生产提供了参考.     

Calculation of Phase Transformation Kinetics from Dilatation Curves

The structure of a steel changes with temperature due to phase transformations. This phase change is generally companied by a variation in the specific volume which is exhibited as a departure from the behaviour of the thermal expansion or contraction, at the temperature at which the change occurs. This behaviour can be detected as a change in the dimensions of a suitable test piece, and forms the operating principle of dilatometry. The dilatometric technique may be applicable to the investigation of the p...     

Tempering stability of Fe-Cr-Mo-W-V hot forging die steels

The tempering stability of three Fe-Cr-Mo-W-V hot forging die steels (DM, H21, and H13) was investigated through hardness measurements and transmission electron microscopy (TEM) observations. Both dilatometer tests and TEM observations revealed that DM steel has a higher tempering stability than H21 and H13 steels because of its substantial amount of M₂C (M represents metallic element) carbide precipitations. The activation energies of the M₂C carbide precipitation processes in DM, H21, and H13 steels are 236.4, 212.0, and 228.9 kJ/mol, respectively. Furthermore, the results indicated that vanadium atoms both increase the activation energy and affect the evolution of M₂C carbides, resulting in gradual dissolution rather than over-aging during tempering.     

Zr处理对含Ti低碳微合金钢中氮化物的影响

以含Ti低碳微合金钢为研究对象,通过实验和热力学计算研究了Zr质量分数对钢中氮化物的影响规律.结果表明:随着钢中Zr质量分数由0.0020%增加至0.0200%,钢中氮化物数量密度和面积占比明显增加,氮化物类型逐渐由TiN变为(Ti_○y,Zr_1-○y)N,(Ti_○y,Zr_1-○y)N中Zr/Ti原子数比逐渐增加,(Ti_○y,Zr_1-○y)N由以TiN为主转变为以ZrN为主.热力学计算结果发现精炼过程无TiN,ZrN等氮化物析出,氮化物主要在凝固过程析出.当钢中Zr质量分数为0.0020%时,凝固过程只有TiN析出;而当Zr质量分数≥0.0046%,逐渐有ZrN在凝固末期析出.随着凝固过程温度的降低,(Ti_○y,Zr_1-○y)N具备热力学析出条件.当钢中Zr质量分数由0.0046%增加至0.0200%,(Ti_○y,Zr_1-○y)N开始析出温度逐渐增加,TiN在(Ti_○y,Zr_1-○y)N中占比逐渐减小.最后,当采用Zr-Ti复合脱氧时,钢中Zr质量分数应控制在0.0020%~0.0050%.     

Influence of original microstructure on the transformation behavior and mechanical properties of ultra-high-strength TRIP-aided steel

The transformation behavior and tensile properties of an ultra-high-strength transformation-induced plasticity (TRIP) steel (0.2C-2.0Si-1.8Mn) were investigated by different heat treatments for automobile applications. The results show that F-TRIP steel, a traditional TRIP steel containing as-cold-rolled ferrite and pearlite as the original microstructure, consists of equiaxed grains of intercritical ferrite surrounded by discrete particles of M/RA and B. In contrast, M-TRIP steel, a modified TRIP-aided steel with martensite as the original microstructure, containing full martensite as the original microstructure is comprised of lath-shaped grains of ferrite separated by lath-shaped martensite/retained austenite and bainite. Most of the austenite in F-TRIP steel is granular, while the austenite in M-TRIP steel is lath-shaped. The volume fraction of the retained austenite as well as its carbon content is lower in F-TRIP steel than in M-TRIP steel, and austenite grains in M-TRIP steel are much finer than those in F-TRIP steel. Therefore, M-TRIP steel was concluded to have a higher austenite stability, resulting in a lower transformation rate and consequently contributing to a higher elongation compared to F-TRIP steel. Work hardening behavior is also discussed for both types of steel.     

奥氏体化状态和钒对珠光体型钢轨钢韧性的影响

以重轨钢ＰＤ２和ＰＤ３为对象，重点研究了热轧态和重新热处理状态珠光体的韧性。研究结果表明，奥氏体状态（晶粒大小、成分均匀化及碳化物溶入或析出程度等）及珠光体的形态和片层间距是影响珠光体冲击韧性的主要组织因素。奥氏体晶粒的细化、珠光体片层的细化、奥氏体成分的均匀化及强碳化物形成元素在奥氏体状态的固溶化是珠光体钢韧化的基本途径。     

用超塑性预处理原理细化低碳钢晶粒的研究

利用超塑性预处理细化晶粒原理 ,在低碳钢中加入不同体积分数的第二相粒子ZrC和ZrO2 ,研究了ZrC和ZrO2 粒子体积分数及轧后不同冷却方式对低碳钢组织和力学性能的影响。研究结果表明 ,轧制变形量为 84 %时 ,加入 0 .8%的ZrC粒子 ,采用轧后水冷方式可获得超细组织 ,晶粒尺寸可达到 9.8μm ;加入 0 .2 %的ZrO2 粒子时 ,晶粒尺寸可达 7.8μm。轧后水冷比轧后空冷方式能获得更为细小的晶粒     

几种高速钢使用性能的热扭分析

采用热扭分析方法,模拟实际使用环境条件,测量M_2、M_2AL和301高速钢的弹性变形功和弹塑性变形功,发现M_2AL高速钢比M_2高速钢使用性能优良主要原因是它有更高的弹性变形功和弹塑性变形功。而301高速钢的弹性变形功和弹塑变形功比M_2高速钢低得多,因此不适于制造机用刃具,说明热扭分析方法测定的弹性变形功和弹塑性功是准确评估高速钢的重要参数。     

微量合金元素对5CrNiMo钢淬透性的影响

设计了一种测定高淬透性钢淬透性的加压块端淬试验法,与标准端淬试验法对照进行了仔细的研究,论证了该方法的合理性和实用性。采用这种新方法成功地对国内外五种 5CrNiMo 钢进行了淬透性对比研究。结果表明:在 5CrNiMo 钢中加入0.11％的钒,并把铬钼含量控制在标准上限能有效地提高其淬透性;经改进后的国产 5CrNiMo钢的淬透性已经赶上和超过德国、日本同类钢的实物水平。