Ce对00Cr17高纯铁素体不锈钢再结晶及晶粒长大的影响

利用显微硬度计、金相显微镜、差热分析仪和XRD研究了稀土元素Ce对00Cr17高纯铁素体不锈钢再结晶及晶粒长大的影响.结果表明,00Cr17钢中加入Ce降低了再结晶温度,促进了再结晶的发生.主要是由于微量Ce固溶到00Cr17钢中引起晶格畸变,增加了冷变形储存能,从而增大了00Cr17钢的再结晶驱动力.00Cr17钢中加入Ce增加了晶粒长大激活能,减小了晶粒生长指数,阻碍了00Cr17钢的晶粒长大,这是由于Ce偏聚到晶界,增大晶界运动的阻力.     

Effect of Cu on the boron segregation at grain boundaries and vacancy-type defects in ultra-low carbon micro-alloy steels

By thermal neutron irradiation particle tracking autoradiography(PTA)technique,the development of boron segregation at grain boundaries in ultra-low carbon micro-alloy steels was investigated during cooling from 1150°C to 850°C,and the effect of Cu on boron segregation at grain boundaries was discussed.By positron annihilation lifetime(PAL)technique,the changes of vacancy-type defects with temperatures and the effect of Cu on vacancy-type defects in the cooling process were discussed.Results show that,the concentration of boron at grain boundaries increases rapidly at the beginning of the cooling;after that,it begins to decrease;and then,it increases gradually again.The addition of Cu not only increases the concentration of boron at grain boundaries but also speeds up the development process of boron segregation at grain boundaries.During the continuous cooling process,the addition of Cu significantly affects the change of vacancy-type defects with temperatures in ultra-low carbon micro-alloy steels.     

高碳钢中片状马氏体的分形(Fractal)特征

本文研究了T12钢不同温度加热淬火后得到的片状马氏体组织,认为在一个奥氏体晶粒内部,片状马氏体呈分形结构。实验表明在不同的相区,随淬火加热温度增加,分形维数D_f增加。在T=820℃附近D_f有一较大的变化,是由于A+FesC两相区向单相A区的转变所引起,同时也讨论了分形维数D_f与淬火组织硬度之间的关系。     

GH4169合金δ相的析出动力学研究

采用X射线衍射技术测定了GH4169合金中δ相在900℃、930℃时的析出动力学,并采用光学显微镜进行组织观察,结果表明：δ相的形核位置和形核方式与时效温度有关.当时效温度在900℃时,δ相主要在晶界和孪晶界上形核析出,而晶内颗粒状δ相由时效初期析出的亚稳态γ″相转变形成;当时效温度为930℃时,δ相不仅可以在晶界和孪晶界形核析出,还可以从基体γ莫直接形核析出,并且随着时效时间的延长,δ相逐渐向晶内生长,最终形成魏氏体δ相.当时效温度一定时,δ相的析出含量与时效时间满足Avram i方程.     

低铬X70管线钢组织及其抗CO2

为了明确Cr的质量分数高低对埋地用输油输气管线钢性能的影响,设计了4种Cr的质量分数的X70管线钢,研究了不同Cr的质量分数下管线钢组织及其力学性能,并采用高温高压反应釜进行了实验钢的CO₂腐蚀试验.结果表明：钢中加入0.1%~0.8%的Cr后,其组织均由针状铁素体和准多边形铁素体构成,Cr元素均呈现明显的沿晶界分布状态;随着Cr的质量分数的增加,钢板强度随之升高,晶界中Cr分布密度随之增大,Cr（OH）₃在腐蚀产物膜中的富集量增加,促使钢板的平均腐蚀速率降低;同时由于Cr（OH）₃可以有效阻碍阴离子穿透腐蚀产物膜,因而大大减少了Cl-的催化作用导致的点蚀,使得钢板点蚀速率明显降低.     

超高强钢热冲压硬化机理

以22MnB5钢为研究对象,分析了超高强钢热冲压成形过程中相变硬化机理。根据热模拟试验结果建立了加热过程奥氏体晶粒尺寸计算模型和变形抗力模型。采用有限元法对材料热冲压同时淬火冷却过程的温度场进行了分析,采用相变动力学模型分析了热成形过程中发生的相变,以及显微组织和力学性能之间的关系。结果表明:形成均匀细小板条马氏体组织的最佳工艺为900～950℃加热5min,超过30℃/s快速淬火并保压8s左右。     

无取向硅钢晶粒与晶界特征的EBSD分析

借助电子背散射衍射（EBSD）技术测量和计算了无取向硅钢再结晶退火后再结晶百分比、晶粒尺寸、取向差分布等参数,分析了再结晶退火温度对无取向硅钢晶粒大小、微观取向和耐蚀性的影响。结果表明,3个温度（810、840、880℃）下退火3 min后,再结晶均充分完成。随着退火温度的升高,再结晶晶粒尺寸长大。拥有{100}面织构的晶粒比其他取向晶粒具有更好的耐蚀性,侵蚀后晶粒凸出于试样表面。880℃退火后的小尺寸晶粒周围多为小角度晶界,不易迁移,不易被侵蚀。     

Elevated-temperature properties of one long-life high-strength gun steel

The hardness, tensile strength and impact toughness of one quenched and tempered steel with nominal composition of Fe0.25C-3.0Cr-3.0Mo-0.6Ni-0. 1Nb (mass fraction) both at room temperature and at elevated temperatures were investigated in order to develop high-strength steel for long-life gun barrel use. It is found that the steel has lower decrease rate of tensile strength at elevated temperature in comparison with the commonly used G4335V high-strength gun steel, which contains higher Ni and lower Cr and Mo contents. The high elevated-temperature strength of the steel is attributed to the strong secondary hardening effect and high tempering softening resistance caused by the tempering precipitation of fine Mo-rich M2C carbides in the α-Fe matrix. The experimental steel is not susceptible to secondary hardening embrittlement, meanwhile, its room-temperature impact energy is much higher than the normal requirement of impact toughness for high strength gun steels. Therefore, the steel is suitable for production of long-life high-strength gun barrels with the combination of superior elevated-temperature strength and good impact toughness.     

Effect of quenching and partitioning process on MA constituent in Nb-bearing HSLA steel

The effect of quenching-partitioning (Q-P) process on martensite-austenite (MA) constituent is investigated by the thermo-analysis simulator for a niobium-bearing HSLA steel. The process includes quenching from 950 ℃ to the intermediate temperature of 350-550 ℃ at the rate of 30 ℃/s and subsequent reheating at the rate of 20-50 ℃/s and partitioning at 660-800 ℃. The microstructure is characterized by nano probe, EBSD, colored metallograph, optical microscope and graphic analytic method. The results show that the improvement of distribution homogeneity of MA in microstructure, the diminishment of the MA average grain size and increment of the MA volume fraction is caused by the intermediate temperature decrease, the reheating rate increase and a proper partitioning temperature. The volume fraction of MA is up to 7.9% while the sample is quenched to 450 ℃, reheated at 50 ℃/s and partitioned at 750 ℃. The grain is granular or equiaxed in shape and the average grain size of MA is about 0.77-1.48 μm after treated by Q&P process. The grains tend to be coarse and with sharpy-angle as the intermediate temperature is up and the reheating rate and the partitioning temperature rises. The MA volume fraction depends on the untransformed austenite volume fraction after quenching and carbon diffusion time and temperature during partitioning process.     

Effects of heat treatment on structures and properties of high speed steel rolls

The effects of quenching temperature, cooling pattern, temper temperature and temper times on the structure and properties of high speed steel (HSS) rolls have been investigated. The results show that, when the quenching temperature is lower than 1050℃ the hardness of HSS increases with the quenching temperature increasing in oil cooling, but when the quenching temperature exceeds 1100℃ the hardness decreases. In the conditions of salt bath cooling and air cooling, the effect of quenching temperature on the hardness is similar to the above law, but the quenching temperature obtaining the highest hardness is higher than that in oil cooling. When the temper temperature below 350℃ the hardness of HSS has a little change, when above 475℃ the hardness will increase with the temper temperature increasing, and the highest hardness is obtained at 525℃. When the temper temperature continues to increase, the hardness decreases. Twice temper has little effect on the hardness, but three times temper decreases the hardness. HSS in air cooling has lower hardenability, oil cooling can easily produce crackle, and HSS quenching in salt bath has high hardenability and excellent wear resistance.     

热处理工艺对低合金耐磨钢组织和性能的影响

通过对低合金耐磨钢热处理工艺试验．研究了不同淬火和回火温度对材料组织和性能的影响．结果表明：经过920℃／30min水淬＋260℃／2h回火处理后,试样晶粒细小,组织为板条马氏体、碳化物和少量残余奥氏体,并具有最佳的冲击韧性和硬度．     

加热温度对HRB400钢奥氏体晶粒度的影响研究

介绍了铌微合金化处理工艺HRB400钢在不同的加热温度下对奥氏体晶粒度的影响。结果表明:在相同的加热温度下Nb含量高的奥氏体晶粒细,加入Nb合金有利于阻止加热时的奥氏体晶粒长大;Nb含量较高时轧制加热温度应略高于1150℃;Nb含量较低时轧制加热温度应略高于1050℃~1100℃。     

Structure change of 430 stainless steel in the heating process

The microstructure analysis was employed for the ferrific stainless steel （SUS430） with the carbon content from 0.029wt% to 0.100wt% under the simulated heating process condition. The higher carbon sample （430H） contains the duplex phase microstructure at the temperature of 1150℃; on the other hand, the lower carbon content sample （430L） does not touch two phase area even at the temperature of 1450℃ and has the single phase ferritic microstructure. The carbon content need be well controlled for the 430 ferritic stainless steel since it can significantly affect the heating process curve, and the heating process may not be done in the two phase area due to the uncontrolled carbon content. With the low carbon content and the proper soaking time, the grain size is not sensitive to the heating process temperature and the soaking time. In the present heat treatment experiments, the soaking time is about 10 min, and the processing parameters can be chosen according to the requirement of the gross energy, the efficiency and the continual forming. 2008 University of Science and Technology Beijing. All rights reserved.     

提高40Cr钢强度和韧性的新工艺

本文研究了40 Cr钢的热处理新工艺,即经过1280℃淬火,获得淬火板条马氏体的亚结构,然后再经810℃第二次淬火,获得细晶的板条马氏体。试验结果表明,屈服强度和冲击韧性显著提高,并且抑制了低温(350℃)回火脆性。 本文还对改善性能以及抑制回火脆性的微观机理进行了分析,认为粒状碳化物形态是改善机械性能、抑制回火脆性的主要原因。     

渗碳对Fe_3Al基合金力学性能的影响

通过研究 F e3A l基合金经不同时间渗碳后其室温力学性能和高温力学性能的变化 ,发现碳的渗入使合金的强度与延伸率都有所下降 ,同时 F e3A l合金的有序转变温度 Tc升高 .C以固溶形式进入F e3A l合金 ,当 C渗入量超过其固溶度时 ,将在晶界处析出碳化物从而降低合金的强度与塑性     

Effect of solid-solution temperature on the microstructure of Fe-Ni based high strength low thermal expansion （HSLTE） alloy

The influence of solid-solution temperature on the dissolution of carbide precipitates, the average grain size and the microhardness of the austenite matrix in an Fe-Ni based high strength low thermal expansion （HSLTE） alloy was investigated to obtain the proper temperature range of the solid-solution process. The XRD analysis, microstructure observations, and the theoretical calculations showed that the Mo-rich M2C-type precipitates in the Fe-Ni based HSLTE alloy dissolve completely at about 1100℃. The average grain size of the studied alloys increases from 14 to 46 μm in the temperature range of 1050 to 1200℃. The microhardness of the matrix decreases gust for the sake of solid-solution treatment, but then increases later with increasing solution temperature because of the solution strengthening effect.     

合金元素Mo对冷轧双相钢组织的影响

分析Mo微合金冷轧双相钢和普通C-Mn冷轧双相钢在不同双相热处理工艺下微观结构,讨论Mo对冷轧双相钢组织变化规律的影响。实验结果表明：当两种双相钢以1700℃／s冷却时,均获得了铁素体、马氏体双相组织,马氏体均匀分布在铁素体基体上,随着加热温度的升高,普通C-Mn双相钢得到的马氏体体积分数多。当以5．4℃／s冷却时,Mo微合金双相钢得到的马氏体体积分数多;当加热到820℃保温结束后以5．4℃／s的速率冷却时,普通C-Mn钢的组织组成相为铁素体、珠光体、马氏体;Mo微合金钢的组织组成相为铁素体、贝氏体、马氏体;Mo对铁素体晶粒的细化作用不明显。     

终烧温度对陶瓷型芯性能的作用

为了阐明终烧温度与陶瓷型芯性能的关系,利用高温抗折试验机和原位观测手段,研究了不同终烧温度下陶瓷型芯性能的变化.结果表明,对于非定向陶瓷型芯而言,随着终烧温度的提高,室温抗折强度保持稳定,在1 150℃条件下陶瓷型芯的高温抗折强度最高,且其变形抗力逐渐提高;而对于定向陶瓷型芯而言,随着终烧温度的提高,室温抗折强度和高温抗折强度均逐渐降低,且其变形抗力变化不大.根据上述实验结果,非定向陶瓷型芯的终烧温度确定为1 150℃,而定向陶瓷型芯的终烧温度确定为1 120℃.     

Nb变质处理铸造高速钢的组织和性能

在铸造高速钢刀具中添加质量分数为4％的Nb形成孤立粒状碳化物以细化铸态组织,研究了不同固溶温度和回火温度下的组织和硬度.结果显示:固溶处理温度为1 200℃时,碳化物呈孤立粒状均匀分布;低于此温度,晶界上的羽毛状碳化物未能完全溶解,而高于此温度则导致粒状NbC的溶解.回火温度为570℃到580℃时,可获得细针状马氏体和最少量的残余奥氏体;低于此温度,针状马氏体粗大,残余奥氏体量较多.     

淬火处理对激光选区熔化成形S136组织与性能的影响

为了改善激光选区熔化（SLM）成形S136模具钢的性能,对SLM成形的试样进行淬火处理. 采用X射线衍射(XRD)和扫描电子显微镜(SEM),研究淬火温度对SLM成形S136的微观组织、硬度和耐腐蚀性能的影响. 结果表明：SLM成形的S136试样组织由马氏体和少量残余奥氏体组成,经过980、1 020、1 050和1 100 °C的淬火处理之后,原晶界消溶,组织大部分转变为马氏体;淬火处理后试样的硬度得到改善,最高值达到54.24 HRC,比原始成形试样提高了近10%;淬火处理后试样原晶界消溶,耐腐蚀性元素分布均匀使得耐腐蚀性能得到了极大的提升,与原始成形试样相比,腐蚀失重量减少了近97%. 优化淬火处理工艺后表明：采用1 050 °C保温1 h并油淬的淬火处理条件,可以得到最佳的硬度/耐蚀性能匹配.