高锰奥氏体不锈钢的晶界强化

研究了高锰奥氏体不锈钢不同状态下奥氏体晶粒尺寸对硬度的影响，给出了硬度与奥氏体晶粒尺寸的关系式。     

SNCrW钢晶粒度及碳化物的控制研究

SNCrW钢属奥氏体耐热钢,固溶态的奥氏体晶粒度和碳化物的分布是影响其力学性能的主要因素。对该钢进行了热处理和热变形加工试验。结果表明,采用分段加热锻造,即钢锭或钢坯先高温加热,然后再于1150～900℃加热锻造,能有效控制该钢的奥氏体晶粒度和碳化物分布形态。     

Anisotropic Electroplastic Effects on the Mechanical Properties of a Nano-Lamellar Austenitic Stainless Steel

Effects of electropulsing treatment(EPT) on the microstructural evolution and mechanical properties of a cold-rolled 316 L austenitic stainless steel with nano-lamellar structure were investigated.The EPT experiments were carried out with the electric current direction along the rolling direction(RD) and the transverse direction(TD) of the samples,respectively.Significant anisotropic electroplastic effects for the RD and TD specimens,i.e.,reduced hardness/strength and enhanced ductility,were obtained owing to the different recrystallization behaviors of the RD and TD specimens during EPT.The RD specimens after EPT with larger recrystallized grain size and higher volume fraction of recrystallization show lower strength and higher elongation than that of the TD specimens.The main reason might be attributed to the change of the current direction in the two kinds of samples,which results in the different sensitivity of the microstructures to thermal and athermal effects during EPT.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

一种低碳多元空冷贝氏体铸钢的组织与性能

本文以A3废钢为主要原料,添加Si、Mn、Cr和一种廉价的金属等多种合金元素,加入少量Mo、稀土进行微合金化和变质处理,在中频炉冶炼、潮模砂型的条件下,制得10 mm×10 mm×55 mm无缺口冲击试样.经热处理后,获得了以准贝氏体为基体综合性能优良的合金钢.该钢经过奥氏体化后空冷,再经回火处理,分别测试了空冷、回火处理后试样的洛氏硬度、冲击韧性,并在Olympus和扫描电子显微镜(SEM)下观察了其组织形态与断口形貌.试验结果表明,试样经920 ℃保温1 h奥氏体化后空冷、300 ℃保温2 h回火后得到较好的硬度与冲击韧性的匹配,硬度达到HRC 34,冲击韧性高于240 J/cm2,金相组织以准贝氏体为主,含有少量的残余奥氏体.实验证明该钢是一种热处理工艺简便、成本低、可以代替调质钢、提高经济效益的新型钢种.     

Effect of Austempering–Partitioning on the Bainitic Transformation and Mechanical Properties of a High-Carbon Steel

The 1.1C–1.5Si–1.1Mn–1.4Cr–0.5Mo–0.6Al–0.6Co(in wt%) steel was treated, respectively, by isothermal austempering process and newly developed austempering–partitioning–tempering process(A–P–T). After austempering at250, 280 and 300 °C for 38, 20 and 10 h, respectively, the sample microstructures were composed of bainitic ferrite plates and film-like retained austenite with thicknesses between 60 and 150 nm. The highest tensile strength of 2003 MPa and hardness value of 53.9 HRC were obtained for the steel after austempering at 250 °C for 38 h, resulting from the combining effect of super-saturated martensite decarburization and stabilization of bainitic formation. After A–P–T treating(heated at 300 °C for 8 h following water cooling, and then heated at 300 °C for 2 h following air cooling),bamboo leaf-like martensite, primary and secondary bainites and retained austenite were observed. The thickness of the secondary bainitic ferrite plates formed during partitioning is much smaller than that of the primary bainite formed during300 °C austempering. Samples subjected to A–P–T treatment showed improvement in ductility compared to that subjected to austempering.     

Investigation and Modeling of Austenite Grain Evolution for a Typical High-strength Low-alloy Steel during Soaking and Deformation Process

The final mechanical properties of components greatly depend on their grain size. It is necessary to study the grain evolution during different thermomechanical processes. In the study, the real-time austenite grain evolution of a high-strength low-alloy (HSLA) steel during the soaking process is investigated by in situ experiments. The effects of different deformation parameters on the dynamic recrystallization (DRX) kinetic behaviors are investigated by hot compression experiments. Based on the observations and statistics of the microstructures at different thermomechanical processes, a unified grain size model is established to evaluate the effects of soaking parameters and deformation parameters on the austenite grain evolution. Also, the DRX kinetic model and critical strain model are established, which can describe the effects of the soaking process on the DRX kinetics process well. The established grain size model and DRX kinetic model are compiled into the numerical simulation software using Fortran language. The austenite grain evolution of the material under different deformation conditions is simulated, which is consistent with the experimental results. It indicates that the established model is reliable, and can be used to simulate and predict the grain size during different thermomechanical processes accurately.     

三圆截线法测定奥氏体不锈钢平均晶粒度的应用

严格控制试件的取样、磨抛和晶界显示等环节,将可能引起晶界混淆的外在因素(机械滑移、孪晶及基体灰度不均等)降至最低。利用三圆截线法,辅以图像分析软件,实现了奥氏体不锈钢任何形貌晶粒度(均匀、不均匀及混合晶粒)的快速准确测定。     

Grain size effects in the quasi-static fracture resistance of a thermally embrittled RPV steel (annealed microstructures)

The elastic-plastic fracture toughness and crack extension behavior under quasi-static loading regimes of the as-received and several thermally embrittled states of a reactor pressure vessel (RPV) steel were assessed on the basis of microstructural parameters. Through a simple rule of mixture that is typically applied for composite materials, it was found that the equivalent grain size (EGS) of dual-phase annealed microstructures is the controlling parameter of the fracture properties. It was concluded that a Hall-Petch type relationship correlates the J-fracture mechanics criteria to the EGS.     

一种高强韧性钢的纳米结构及其性能

以Cr—Mn—Si为主,添加其它微量元素和稀土元素,研制了一种新型的中碳低合金耐磨钢。试验结果表明,这种新型的低合金高强韧性耐磨钢,其铸态和锻态试样经淬火回火处理后均可得到回火马氏体及少量贝氏体、残留奥氏体及碳化物组织。铸态淬火回火处理的U型缺口试样的冲击韧度αk=37～55J／cm^2,无缺口试样的冲击韧度αk=210～300J／cm^2,其硬度为53～56HRC;锻后淬火回火处理的u型缺口试样的冲击韧度αk=48～70J／cm^2,其硬度为52～54HRC,抗拉强度叽=1850～2000MPa。采用高分辨电镜,对研制钢的纳米结构原子像进行了观察,确定了贝氏体铁素体亚片条的尺寸。     

高强度高韧性钢的热处理与力学性能

研究了真空冶炼低碳Ｎｉ１０Ｃｏ１４Ｃｒ２Ｍｏｌ钢的碳含量，时效温度与力学性能的关系，初步探索了钢中加入稀土，镁元素的作用，试验结果表明，钢中含碳量为０．１６％时，经５１０℃时效，可获得高强度和高韧性：σｂ＝１５８５ＭＰａ，σ０．２＝１４７０ＭＰａ，Ｖ型缺口冲击韧度为５６Ｊ／ｃｍ＾２，平面断裂韧性ＫＩＣ＝１０５ＭＰａｍ＾１／２，钢中添加过量稀土，韧性显著降低，镁对性能影响不大。     

Optimization of Grain Boundary Character Distribution in Fe-18Cr-18Mn-0.63N High-Nitrogen Austenitic Stainless Steel

Grain boundary engineering（GBE） is a practice of improving resistance to grain boundary failure of the material through increasing the proportion of low Σ coincidence site lattice（CSL） grain boundaries（special grain boundaries） in the grain boundary character distribution（GBCD）. The GBCD in a cold rolled and annealed Fe-18Cr-18Mn-0.63N high-nitrogen austenitic stainless steel was analyzed by electron back scatter difraction（EBSD）. The results show that the optimization process of GBE in the conventional austenitic stainless steel cannot be well applied to this high-nitrogen austenitic stainless steel. The percentage of low ΣCSL grain boundaries could increase from 47.3% for the solid solution treated high-nitrogen austenitic stainless steel specimen to 82.0% for the specimen after 5% cold rolling reduction and then annealing at 1423 K for 10 min.These special boundaries of high proportion efectively interrupt the connectivity of conventional high angle grain boundary network and thus achieve the GBCD optimization for the high-nitrogen austenitic stainless steel.     

复合变质中锰钢韧性提高研究

通过Nb N RE Si-Ca复合变质处理，获得高韧性中锰奥氏体钢，研究结果表明；复合变质剂使钢的氧化物总量从原来的0．035％降到0．007％，硫化物总量从原来的0．029％降到0．01％，夹杂物圆整度从1．43变为1．04NbN和Nb2C可在液态金属中形成。复合变质中锰奥氏体钢的冲击韧度，裂纹形成功和裂纹扩展功分别比原来提高了263％、288％和232％。     

货车转向架用B~+钢壁厚对力学性能影响的研究

以铁路货车转向架主要铸件的材质B~+钢为研究对象,通过对不同壁厚B~+钢铸造试块的不同部位进行标准拉伸和冲击试验,研究其壁厚变化对其力学性能的影响.实验结果表明,B~+钢壁厚在14～35mm区间变化时,无论是试块的边缘部位还是中心部位,抗拉强度和冲击功均无明显变化;当壁厚在35～50mm区间变化时,其试块边缘部位的抗拉强度和冲击功随着壁厚的增加无明显变化,而试块中心部位的抗拉强度和冲击功明显降低;当壁厚增加到50mm时,抗拉强度和冲击性能只有其对应边缘部位的30%左右.     

高Cr铁素体耐热钢与奥氏体耐热钢的异种材料扩散连接接头组织演变及力学性能

开展了高Cr铁素体耐热钢与TP347H奥氏体耐热钢的异种材料真空扩散连接实验,研究了扩散连接时间及焊后热处理工艺对扩散影响区组织演变和力学性能的影响。结果表明,随着扩散连接时间的延长,界面结合率逐渐增加。变形储存能差异与位错滑移的相互作用下,在扩散连接界面处发生动态再结晶形成了细小晶粒,最终演化成锯齿状的界面结合形态。扩散连接区晶界与晶粒内部析出细小弥散的MX、M23C6相。焊后热处理之后扩散连接区的晶粒进一步细化,位错相对稳定化,位错密度减少,小角度晶界增多,元素扩散更加充分。对获得的扩散连接试样进行不同温度的拉伸实验,断裂位置均位于基体中,说明获得了高质量的异种材料扩散连接接头。     

锻后热处理对AF1410钢冲击韧性和晶粒度的影响

研究了AF1410钢锻后不同热处理温度和保温时间对冲击韧性和晶粒度的影响。结果表明,随锻后热处理温度的降低,AF1410冲击吸收能量先升高后降低,并且AF1410晶粒度尺寸逐渐减小,但减小幅度变小且趋于均匀化。同一锻后热处理温度下不同保温时间对AF1410冲击韧性有一定的影响,但影响不大,而对晶粒度几乎无影响。     

Application of Grain Boundary Engineering to Improve Intergranular Corrosion Resistance in a Fe–Cr–Mn–Mo–N High-Nitrogen and Nickel-Free Austenitic Stainless Steel

Optimization of grain boundary engineering(GBE) process is explored in a Fe–20Cr–19Mn–2Mo–0.82N high-nitrogen and nickel-free austenitic stainless steel, and its intergranular corrosion(IGC) property after GBE treatment is experimentally evaluated. The proportion of low Σ coincidence site lattice(CSL) boundaries reaches 79.4% in the sample processed with 5% cold rolling and annealing at 1423 K for 72 h; there is an increase of 32.1% compared with the solution-treated sample. After grain boundary character distribution optimization, IGC performance is noticeably improved. Only Σ3 boundaries in the special boundaries are resistant to IGC under the experimental condition. The size of grain cluster enlarges with increasing fraction of low ΣCSL boundaries, and the amount of Σ3 boundaries interrupting the random boundary network increases during growth of the clusters, which is the essential reason for the improvement of IGC resistance.     

超细晶奥氏体不锈钢的研究状况及问题

详细介绍了超细晶奥氏体不锈钢技术,综述了奥氏体不锈钢力学性能、晶间腐蚀性能、应力腐蚀性能、点蚀和缝隙腐蚀性能与晶粒尺寸之间的关系,指出了超细晶奥氏体不锈钢研究存在的问题.     

高锰钢与钢轨钢二次闪光对焊接头的组织和冲击韧性

通过工艺试验,力学性能检验以及光镜、电镜、Ｘ射线衍射、电子探针等湿微分析手段,对高锰钢与钢轨钢二次闪光对焊接头的组织形态和冲击韧性进行了系统研究,确定了接头各区的组织形态和冲击韧性的变化情况,并提出了高锰钢与钢轨钢二次闪光对焊时改善钢轨钢焊接热影响区冲击韧性的工艺措施。研究表明,利用过渡材料来实现焊接性差、万分和物理性能相差悬殊的高锰钢与钢轨钢的焊接是一种行之有效的工艺措施。     

再加热温度对400MPa级超级钢组织和性能的影响

对400MPa级超级钢试样在不同温度下加热保温5min,并分别进行空冷和水冷,然后进行组织分析和性能检测。结果表明：空冷条件下,随加热温度的增加,晶粒长大严重,力学性能明显下降;而在800℃时不仅珠光体发生了明显的球化,其强度和硬度值下降也最为明显。水冷条件下,700℃以前,其组织和性能与空冷条件下基本相同;800℃时珠光体不仅没有发生明显的球化,而且其强度和硬度值还有所提高;900℃以后出现明显淬火组织,力学性能也明显提高。