硅锰系相变诱发塑性钢的热处理工艺研究

应用相变诱发塑性（ＴＲＩＰ）方法强韧化的硅锰系相变诱发塑性钢（ＴＲＩＰ钢），是经特定的热处理和工艺参数优化处理，控制钢中的残留奥氏体数量及其稳定性，可显著提高钢的力学性能，尤其是塑性，达到强度和塑性的良好匹配，成为一类新型高强韧钢，具有推广应用的极好前景。     

贝氏体等温处理对C-Mn-Al系TRIP钢组织和性能的影响

近年来,汽车制造业发展迅速,制造商要求汽车用钢在保证高强度的基础上又具有良好的塑性,相变诱导塑性钢因其具有较高的强塑积综合指标而进入了汽车用钢研发者的视线. 相变诱导塑性钢,即 TRIP钢 (Transformation Induced Plasticity Steel),室温时由铁素体、贝氏体、残余奥氏体及马氏体等多...     

屈强比对塑性影响的研究

由于低屈强比钢具有良好的成型性,因此对屈强比存在这样的认识,即钢的屈强比越低,则钢的塑性就越好。然而,通过对Mn-B钢的控轧控冷试验发现,在满足化学成分和屈服强度相同的前提下,低屈强比钢的塑性反而低于高屈强比钢。经研究认为,具有低屈强比的钢,仅是表征该钢具有较大的均匀延伸,而钢的塑性是由均匀延伸和缩颈后的局部集中延伸共同所决定。     

40Cr钢的补焊

40Cr钢是机械制造工业中常用的钢种之一，调质处理后，具有硬度高、塑性良好和低温冲击韧性、低的缺口敏感性及高疲劳强度。该钢还适合碳氮共渗和高频淬火处理，切削性能和淬透性好，但冷变形塑性和焊接性较差。常用来制造重要的高强度调质零件，如齿轮、轴、紧固件等。当零件磨损后，重新购进成本太高，经过大量的实践，总结出以下补焊方法。40Cr钢的化学成分见表1。     

PMS镜面钢的超塑性与超塑成形

研究新型塑料模具钢ＰＭＳ镜面钢的超塑性，并应用于模具成形。该钢在６３０～６７０℃变形温度范围内和较宽的应变速率范围内具有较好的超塑性能，可一次成形出精度较高的模具，证明其具有较好的应用效果。     

钢结硬质合金适用性的表征

为了表征作为工具材料用于金属塑性成形的适用性，研究了钢结硬质合金的机械性能。在所研究的钢结硬质合金中ＴｉＣ的含量为４０￣８０％重量（５１￣８６％体积）。用作金属粘结剂的有可硬化马氏体钢、奥氏体钢与具有中间结构（贝菌体）钢。这些合金的不同性能，像硬度、强度、塑性、应变能与断裂韧性的研究，及与通用的ＷＣ－Ｃｏ和ＴｉＣ－（Ｎｉ，Ｍｏ）硬质合金的比较，使人们得以推荐它们的适用领域。     

热处理工艺对低碳硅锰TRIP钢力学性能的影响

低碳硅锰钢经临界区等温淬火，残留有大量的奥氏体。该钢在Ma～Md温度之间形变，因钢中大量稳定的残余奥氏体的应变诱导马氏体相变和相变诱发塑性(TRIP)，可获得高的强度、塑性以及良好的强度与塑性的配合。通过对其力学性能测试与显微组织分析，对低碳硅锰钢热处理工艺及钢中残余奥氏体的相变诱发塑性行为进行了探讨。结果表明：钢在400℃等温淬火的热处理工艺，所获得的力学性能最佳。     

高性能海底管线用钢试验研究

海底管线用钢要求具有较大的均匀塑性变形延伸率、较低的屈强比等,该管线钢的高强度与高塑性匹配主要来源于双相组织的作用。针对海底管线用钢的组织和塑性变形能力进行了研究。结果表明,海底管线用钢的母材组织由铁素体、贝氏体及少量MA岛构成,其组织形貌与控轧控冷工艺密切相关。细化的双相组织具有良好的塑性指标和较低的屈强比,保证了管线钢具有良好的强塑性匹配。     

LD钢冷挤压模强韧化处理研究

研究了ＬＤ钢经不同热处理后的组织和力学性能的关系，对断口进行了扫描电镜形貌分析。结果经优化处理的ＬＤ钢模具具有强度、硬度、塑性及韧性的良好配合，模具使用寿命大幅度提高。     

电站锅炉用T91钢热穿孔性能的研究

对T91钢的高温塑性和穿孔性能进行了试验研究。研究表明:在1100～1200℃温度范围内,该钢具有良好的塑性;在1100～1250℃温度范围内具有良好的穿孔性能。     

Structure and Properties of Low-Alloy High-Nitrogen Martensitic Steels

Special features of structure formation and mechanical properties of low-alloy martensitic steels with superequilibrium content of nitrogen and low content of carbon are considered. Experimental data on the effect of the temperature of heating for hardening and tempering on the structure, strength, and ductility of these steels are presented. The advantages and disadvantages of the introduction of nitrogen into low-alloy martensitic steels instead of carbon are discussed. It is shown that steel 10Kh3A combines high strength with high ductility. This steel is considered as a material for heavily loaded parts and nonwelded structures instead of high-strength steels alloyed with Ni, Mo, V and other expensive and scarce elements.     

Hardenability testing of steels when gas quenching is applied

Abstract

The common test for assessing hardenability is the standardised Jominy end-quench test according to ASTM-A255 or DIN-EN 50191. This test is applied essentially for non-alloyed and low alloyed structural steels, when quenched in liquid quenchants, but it is not applicable for high alloyed (air hardening) steels, because the cooling rate at the opposite end of the Jominy specimen is higher than the critical cooling rate of those steels. Today there is no a standardised method to test and evaluate the hardenability of high alloyed steels. Nowadays, not only high alloyed steels, but also some low alloyed structural steels are quenched by high pressure gas quenching (HPGQ) in vacuum furnaces. Obviously there is need from one side to develop a standardised method for testing and evaluation of hardenability for high alloyed steels when they are gas quenched, and from the other side to establish a database for hardenability of low-alloyed structural steels when they are quenched in vacuum furnaces by HPGQ, i.e. at different high pressures and different flow velocities. Corresponding equipment that can be used to satisfy both requirements is discussed.     

Cu,P,Cr 和 Ni 对低碳钢耐蚀性的影响简

选择Cu-P-Cr-Ni钢、Cu-P-Cr钢和Q235碳钢,在0.01 mol/L的NaHSO3溶液中进行周期浸润、阻抗谱和极化曲线实验,研究了Cu-P-Cr-Ni系合金钢相比Q235碳钢在模拟工业大气(SO2)环境下的耐腐蚀性能;利用SEM,EPMA面扫描和XRD分析腐蚀锈层的形貌、组成及Cu,Cr和Ni的元素分布情况。结果表明:Cu-P-Cr-Ni系钢的腐蚀诱发敏感性最低,其次为Cu-P-Cr钢,腐蚀速率分别为Q235碳钢的59.5%和52.8%;锈层分为内、外两层,致密的内锈层明显发生Cu的颗粒状、Cr的团聚状富集,外锈层主要有Cr的富集,Ni富集不明显。Cu和Cr等的富集可形成致密的内锈层,提高低碳钢的耐蚀性。     

Improved Machinability in Hard Milling and Strategies for Steel Development

The synergetic advantage of tailoring alloyed steels to improve their machinability in the hardened (30 ∼55HRC) state is the focus here. Results from milling tests and systematic study of steel microstructure and tool wear mechanisms using high resolution microscopy (FEG-SEM) and EDS clearly indicates that traditional machinability improvement treatments are not always adequate here. In high alloyed hot working steels, suitable primary carbides distribution could be better than inclusion modification. In low alloyed steels secondary carbide density appears to be critical and correlates well with machinability. The study also points to strategies for steel development and their efficient hard milling.     

Review of the Effects of Hydrogen in Steel

Hydrogen retained in steel may result in important defects, particularly in heavy sections of killed carbon steels and alloyed steels.     

Erosion resistance of Fe-C-Cr weld surfacing layers

Fe-C-Cr weld surfacing layers with different compositions and microstructures can be obtained by submerged arc welding with welding wire of the low carbon steel and high alloy bonded flux. With the increase of Cr and C in the layers the microstructures are changed from hypoeutectoid steel, hypereutectoid steel to hypoeutectic iron and hypereutectic iron. When the weld surfacing layers belong to the alloyed cast irons the erosion resistance can be raised with the eutectic increase and the austenite decrease. Good erosion resistance can be obtained when the proportion of the primary carbides is within 10 %. The experimental results lay a foundation to make double-metal percussive plates by surfacing wear resistant layers on the substrates of the low carbon steels.     

Effect of Alloy Composition on Carburizing Performance of Steel

This paper investigates the effect of alloy composition on the gas carburizing performance of AISI 1018, 4820, 5120, and 8620 steels. The mass-transfer coefficients and carbon diffusivities were calculated from experimental measurements using direct flux integration. Although steels with high concentration of austenite-stabilizing elements (Si, Ni) increased carbon diffusivity in austenite, they significantly reduced the kinetics of carbon transfer from the atmosphere to the steel surface and resulted in lower weight gain. Despite lowering the carbon diffusivities, steels alloyed with carbide-forming elements (Cr, Mo) significantly increased the mass-transfer coefficient in the atmosphere and enhanced the rate of carbon profile evolution. The experimentally determined carbon diffusivities were in good agreement with the carbon diffusivities obtained from the thermodynamic and kinetic databases in DICTRA. Overall, using the concentration dependent mass-transfer coefficient and carbon diffusivity in various alloy steels helped explain the experimentally observed variations in the carbon concentration profiles and the effective case depths. Recommendations are made to help achieve better case depth uniformity within a carburizing workload.     

Influence of processing conditions on structural characteristics of hybrid plasma surface alloyed austenitic stainless steel

A hybrid plasma surface alloying process has recently been developed for austenitic stainless steels to improve their surface hardness, wear resistance and corrosion resistance. The process is carried out in nitrogen and methane gas mixtures at temperatures below 450°C and facilitates the simultaneous incorporation of nitrogen and carbon into the surfaces of austenitic stainless steels, forming a dual layer structure with an extremely hard nitrogen-enriched layer on top of a hard carbon-enriched layer. The present paper discusses the influence of three most important processing parameters, i.e., gas composition, temperature and time, on the structural characteristics of the alloyed zones produced on AISI 321 stainless steel, in terms of layer morphology, growth kinetics and chromium compound precipitation. It was found that the development of the alloyed layers is diffusion-controlled, and under proper processing conditions, a precipitation-free dual-layer structure can be produced, with nitrogen and carbon dissolved in the relevant layer forming N-expanded austenite and C-expanded austenite respectively. Based on the experimental results, a threshold temperature-time curve has been established for the investigated austenitic stainless steel.     

Mechanical and Metallurgical Evaluation of Carburized, Conventionally and Intensively Quenched Steels

Steels subjected to carburizing, quenching, and tempering are widely used for components that require hardness and superficial mechanical resistance together with good core toughness. Intensive quenching is a method that includes advantages including crack prevention, increased mechanical resistance, and improvement in fatigue performance when subjected to very fast (intensive) cooling. However, achieving these advantages requires the formation of sufficiently high surface compressive residual stresses and fine grains at the core of steel components. If the cooling rate is sufficiently high after intensive quenching, then low-hardenability, killed plain carbon steels may be used instead of higher-cost, low alloy steels because compressive residual stresses are formed at the surface of steel parts. The objective of this study was to compare between carburized non-killed AISI 1020 steel samples, which were not modified by Al that were subsequently conventionally and also intensively quenched to determine the effect of quenching on achieving the necessary formation of fine grain size. For comparison, carburized AISI 8620 steel test specimens were conventionally quenched. After quenching, all test specimens were characterized by metallurgical and mechanical analyses. The results of this study showed that when the two quenching methods were compared for carburized non-killed AISI 1020 steel, intensive quenching method was found to be superior with respect to mechanical and metallurgical properties. When comparing the different steels, it was found that intensively quenched, non-killed, AISI 1020 steel yielded grain sizes which were three times greater than those obtained with conventionally quenched, carburized AISI 8620 steel. Therefore, the benefits of intensive quenching were negated. These results show that plain carbon steels must be modified by Al to make fine grains if intensively quenched plain-carbon steel is to replace alloyed AISI 8620 steel.     

空冷贝氏体钢摆锤

对中碳和中高碳系贝氏体钢在不同热处理状态下的组织进行了观察。研究钢的铸态和正火态均可得到以贝氏体或贝氏体／马氏体为主的组织。加入微量元素可使钢的组织显著细化。经低温回火或正火回火处理，铸态显微组织获得了改善，提高了冲击韧度。用研制的贝氏体钢制作产品工艺简单，性能良好，铸成的摆（板）锤粉碎矿石的使用寿命为高锰钢摆锤寿命的２．５倍，成本降低２０％。