强磁场下保温时间对Fe-1.1％C钢中“反常”组织的影响

研究了12 T磁场下910℃保温不同时间(5,10,30和60 min)对高纯Fe-1.1％C钢中“反常”组织形貌及宏观硬度的影响.结果表明:强磁场下“反常”组织面积分数随保温时间的延长而减小;这是由于保温时间的延长扩散较充分,析出时二次渗碳体析出较慢所致.宏观硬度随保温时间的延长而增加.在相同奥氏体化保温时间下,强磁场热处理样品与无磁场热处理样品相比,“反常”组织面积分数明显增加,样品宏观硬度值下降.     

热处理工艺对1Cr12Ni3Mo2VN耐热钢力学性能的影响

研究了热处理工艺对1Cr12Ni3M02VN钢力学性能的影响。结果表明，淬火温度超过1030℃时．钢的奥氏体晶粒显著长大，导致抗拉强度和冲击韧度都显著降低；淬火加热时间即奥氏体化时间为0．5～1h时，钢的抗拉强度和冲击韧度均明显下降；淬火加热时间超过1h，二者的变化不大。若淬火和回火冷却速度过低，则沿晶界析出碳化物M23C6，从而导致冲击韧度明显下降。     

多类型超细碳化物DM7S钢的合金设计及其特性

根据碳化物随温度变化的规律,并结合热力学相平衡计算,设计的多类型碳化物DM7S钢在常规的热处理工艺条件下,碳化物具有超细化特性.DM7S钢以840℃退火,碳化物具有多种类型(M3C,M7C3,M23C6,M6C,MC).根据各种类型碳化物在奥氏体中溶解的热力学和动力学条件差异,淬火后保留不同类型和一定数量的细小碳化物,提高耐磨性能.DM7S钢1080℃以上淬火,500～560℃回火时出现二次硬化效应,最高硬度接近64HRC.     

合金元素对SKD61钢中析出相热力学的影响

采用Thermo-calc热力学计算软件,对SKD61钢在400～1600℃存在的平衡相进行了热力学计算,探讨了不同合金元素含量对回火析出相析出行为的影响,在此基础上设计出热处理工艺,并对热处理试样中的析出相经电解腐蚀后进行扫描电镜(SEM)和EDS研究。计算结果表明:SKD61钢中平衡析出相主要为MC、M7C3、M6C和M23C6,试样回火后的稳定析出相为MC和M23C6,合金元素V、C对MC相和M23C6相影响最大。SKD61钢热处理后的结果显示,该模具钢较合适的淬火温度区间为(1040±20)℃,回火温度的确定应以不出现粗大的M23C6碳化物相为宜。     

12Cr2Mo1V钢回火的显微组织及力学性能研究

采用力学性能检测、显微组织观察等方法,研究了回火热处理及焊后热处理对12Cr2Mo1V钢组织及力学性能的影响。试验结果表明:在回火及焊后热处理过程中,在晶界上会有析出相M23C6析出。保温时间越长,晶界上M23C6越多;而M23C6在晶界析出是导致12Cr2Mo1V钢力学性能下降的主要原因。     

Cr含量对高碳中合金工模具钢组织与性能的影响

对两种不同Cr含量的高碳中合金工模具钢的组织与性能进行研究.结果表明,两种钢820 ℃退火时均存在M23C6、M6C和MC三种碳化物.Cr含量较高的钢中M23C6碳化物的相对数量较高,碳化物较细.奥氏体化过程中,由于Cr含量低的钢中存在大块M6C碳化物,造成淬火未溶碳化物尺寸偏大.Cr含量较高的钢中M23C6碳化物大量溶解,提高了基体中合金元素的固溶量,在200～300 ℃回火硬度保持在59～60 HRC,具有良好的抗回火性.     

强磁场下时效处理对铸造镍基高温合金K52中碳化物的影响

针对时效处理铸造镍基高温合金K52的碳化物,研究了其在强磁场作用下的组织形貌与化学成分变化规律。结果表明:在不同磁场条件下时效处理后,合金中碳化物MC和M23C6的组织形貌与分布基本相同,强磁场的施加对碳化物的组织形貌与分布并未产生显著影响,但经强磁场条件下时效处理后,MC和M23C6中强碳化物形成元素W、Mo、Nb和Ti含量有所增加,而弱碳化物形成元素Cr和非碳化物形成元素Co、和Ni含量显著降低。分析指出强磁场的施加可能提高了强碳化物形成元素与C间的亲和力,增强了其形成碳化物的倾向;同时其可能减弱了弱碳化物形成元素和非碳化物形成元素与C间的亲和力,从而使其在碳化物中存在的倾向也进一步降低。     

国产T23钢高温时效时组织和力学性能的研究

采用光学显微镜、扫描电镜、透射电镜观察和拉伸、冲击试验等方法,研究了国产T23钢在600 ℃时效时的组织变化和力学性能.结果表明,T23钢在600 ℃时效时随着时效时间的延长,T23钢中M23C6型碳化物不断粗化,粒状贝氏体形貌逐渐退化.时效时间较短时,主要是M23C6型碳化物粗化引起T23钢力学性能下降;时效时间较长时,主要是粒状贝氏体形貌的变化导致T23钢力学性能下降,同时,M23C6的球化及其向M6C的转变、亚晶的形成和W、Mo固溶强化的降低加快了T23钢力学性能的下降.     

热处理对Inconel690合金晶粒变化和晶界析出物的影响

研究Inconel690合金在不同的热处理条件下晶粒大小和晶界析出物.结果表明:当固溶处理温度低于1100℃时,晶粒尺寸变化不大,当温度超过1150℃时,晶粒开始显著长大,建议固溶处理应在1100℃以下.Incone1690合金经固溶处理和特殊热处理(TT处理)后,晶界的主要析出物和沉淀物为Ti(C,N)和M23C6,析出物尺寸随热处理温度的升高而增大,分布的形态主要呈断续和半连续状.     

铁素体/马氏体钢P92在形变热处理过程中析出相的形成机理

形变热处理(TMT)可以有效改善9%～12%Cr铁素体/马氏体钢的力学性能。为了更好的理解形变热处理对钢材力学性能的影响,尤其是对钢中析出相的影响,本研究利用透射电镜对形变热处理后铁素体/马氏体钢P92中的MX、M23C6和M2X 3种析出相的形成机理进行了着重分析。结果表明,由于富铌/钒的M(C,N)和富铬M23C6碳化物的析出温度高于富铬M2(C,N)碳氮化物的析出温度,且富铬M2X的形核体积自由能的改变量最小,形变热处理过程中富铬M2X相优先在P92钢的基体中析出。     

淬火钢的高温快速回火工艺

采用高温快速回火方法,对40Cr钢及45、T10钢进行了高于Ac1以上温度的高温回火试验,并与传统回火工艺进行了比较,建立了高温回火时间与传统回火温度的对应关系.试验结果表明用高温快速回火后,其组织和力学性能与传统工艺回火后的基本相同,且所用的回火时间可以大大缩短,并可以避免回火脆性.     

Ti微合金化非调质钢中碳化物析出行为及其对再结晶的影响

通过Gleeble-3800热模拟试验机研究了变形温度850~1200 ℃,应变速率0.1 ~10 s^-1条件下Ti微合金化非调质钢的奥氏体动态再结晶行为。分析变形温度、变形速率、碳氮化物的析出行为对奥氏体动态再结晶的影响,计算动态再结晶激活能,获得动态再结晶状态图和热加工图。结果表明,随着Ti含量从0增加为0.042%和0.063%,钢中碳氮化物的析出量分别为0%、0.040%和0.038%,呈现出先增加后减少的趋势,相应的动态再结晶的激活能分别为360.218、394.015和378.247 kJ/mol,0.042%Ti含量的非调质钢激活能最高。通过功率耗散图和塑性失稳图的叠加得到了热加工图,获得了Ti微合金化非调质钢的最佳热加工工艺范围是900~1050 ℃的变形温度,0.1~0.2 s^-1的变形速率和1100~1200 ℃变形温度,0.1~4 s^-1变形速率。     

磁场对25CrMo48V超高强度钢回火组织与力学性能的影响

为研究磁场作用下热处理工艺对超高强度钢组织调控及碳化物种类、形态、尺寸和演变规律的影响,采用OM、SEM、TEM、EBSD和力学性能测试等技术手段研究了磁场作用对含有Nb、V、Ti等微合金元素的25CrMo48V超高强度钢中组织演变与力学性能的影响。试样均在1000 ℃下进行30 min奥氏体化处理,水淬之后在1 T磁场作用下,在200~600 ℃温度范围内回火1 h。结果表明,磁场的施加会抑制马氏体板条合并,促进M₂₃C₆和M₇C₃型碳化物的析出。经外加1 T磁场不同温度回火后,试样的硬度均高于未加磁场的常规回火处理试样,而其强度低于常规回火处理。     

HSLA-100 steels: Influence of aging heat treatment on microstructure and properties

The structural steels used in critical construction applications have traditionally been heat-treated low-alloy steels. These normalized and/or quenched and tempered steels derive strength from their carbon contents. Carbon is a very efficient and cost-effective element for increasing strength in ferrite-pearlite or tempered martensitic structures, but it is associated with poor notch toughness. Furthermore, it is well known that both the overall weldability and weldment toughness are inversely related to the carbon equivalent values, especially at high carbon contents. The stringent control needed for the welding of these traditional steels is one of the major causes of high fabrication costs. In order to reduce fabrication cost while simultaneously improving the quality of structural steels, a new family of high-strength low-alloy steels with copper additions (HSLA-100) has been developed. The alloy design philosophy of the new steels includes a reduction in the carbon content, which improves toughness and weldability.     

HEAT TREATING OF SINTERED Fe—1.5Mo—0.7C STEELS AND THEIR SLIDING WEAR BEHAVIOR

The influence of heat treating on mechanical properties as well as on the sliding wear behavior of sintered Fe-1.5Mo-0.7C steels was experimentally studied. The microstruc-tures of sintered steels change from upper bainite to martensite, tempered martensite, pearlite and lower bainite depending on the heat treating conditions. Heat treating increases the hardness of sintered steels but high tempering temperature, i.e. 700℃, causes the hardness to be even lower than that of the as-sintered ones. The impact energy of sintered steels increases with increasing tempering temperature and arrives the highest at 700℃, while the steels tempered at 200℃ have the highest transverse rupture strength. Austempering results in fair good overall properties, such as hardness, impact energy, and transverse rupture strength. When the sintered steels were austempered, oil-quenched or tempered below 400℃ after quenched, the wear coefficient becomes considerably lower. Fair high hardness, such as HV30 > 380, and structur     

Influence of welding consumables on high cycle fatigue life of flux cored Arc welded high strength,quenched and tempered steel joints

Quenched and tempered (Q&T) steels are prone to hydrogen induced cracking after welding. Austenitic stainless steel (ASS) welding consumables are traditionally used for welding of high hardness, Q&T steels as they have higher solubility for hydrogen in the austenitic phase. The use of stainless steel consumables for a non stainless steel base metal is not economical. Hence, in the present work, an attempt was made to explore alternate consumables for welding Q&T steels. Flux cored arc welding process was used to fabricate the joints using austenitic stainless steel and low hydrogen ferritic steel consumables. The joints fabricated using low hydrogen ferritic steel consumables exhibited superior fatigue performances than the joints fabricated using ASS consumables.     

Alloy carbide precipitation in tempered 2.25 Cr–Mo steel under high magnetic field

The influence of a high magnetic field on carbide precipitation during the tempering of a 2.25 Cr–Mo steel was investigated by means of transmission electron microscopy. As-quenched specimens were tempered at 200, 550 and 700 °C for various times in the absence and presence of a 12 T magnetic field. Experimental results indicate that the applied high magnetic field effectively promotes the precipitation of M₂₃C₆ carbides at low temperature (200 °C) and M₇C₃ and M₂₃C₆ carbides at intermediate temperature (550 °C). The increased Fe content in the M₂₃C₆ and M₇C₃ carbide significantly increases the magnetization. The magnetic Gibbs free energy, which influenced the alloy carbide precipitation behavior, was considered to be mainly determined by the intrinsic magnetization energy for M₂₃C₆ and M₇C₃ carbides. With the increase of the tempering temperature (700 °C), there was no pronounced effect of the high magnetic field on the precipitation sequence and the concentration of substitutional solute atoms in paramagnetic carbides. The investigation of alloy carbide precipitation under high magnetic fields could contribute to a better understanding of phase transformation of alloy carbides and to the heat treatment and fabrication of heat-resistant steels.     

非调质钢的发展现状和应用进展

非调质钢具有节约能源、降低成本、性能优良、绿色环保优点,得到广泛应用。本文概述了非调质钢发展状况和应用前景,综述了非调质钢的分类、化学成分、生产工艺、力学性能和主要应用。在此基础上,探讨了提高非调质钢强韧性的途径及未来发展的方向。     

Modelling functioning of an adaptive industrial robot in arc welding

Steels with elasticity limits between 650 and 680 MPa include thermomechanical steels and quenched and tempered steels. Thermomechanical steels have excellent weldability, but, nevertheless, require fillers with low diffusible H₂ levels, and a rigorous control over the welding operations, due to the molten zone. Quenched and tempered steels require almost automatic recourse to preheating, and frequently post-heating, but at moderate temperatures. The heterogeneity of the commercial range of base metals available, and the poverty of the range of filler materials with very high elasticity limits, are crucial problems. The risk of cold cracking in the molten zone is very high and, sadly, less well understood than that of cold cracking in the HAZ. Given that the maintenance of good mechanical characteristics requires limiting the T _r 800–500, the weldability range is very narrow. The welding of these steels is not intrinsically complex, but requires considerable rigour.     

铬镍钼钢在调质状态下的冲击缺口敏感性

本文用示波冲击弯曲试验、扫描电镜断口分析和金属薄膜透射电子显微分析，研究了高温回火后３４ＣｒＮｉＭｏ和４０ＣｒＮｉＭｏ钢的缺口敏感性。结果表明：Ｖ型缺口试样的裂纹扩展功能较好地反映材料的缺口敏感性。回火温度升高，试验钢的缺口敏感性降低。回火稳定性好的材料缺口敏感性大。