碳化物在高硬度焊缝中的行为研究

用扫描电镜(SEM)、透射电镜(TEM)及能谱分析(EDS)对高碳Nb-Ti-V-Cr-RE系高硬度冷焊焊缝中碳化物形态及分布特点进行了研究，探讨了碳化物形成机理及其作用行为。MC型碳化物在熔滴阶段已大量形成，在熔池中聚集长大，呈颗粒状均匀分布。碳化物的早期形成占有了大量碳元素，避免了二次碳化物网状析出，同时有利于使基体转变为低碳马氏体组织，改善焊缝金属韧性。     

钢轧辊局部冷焊焊缝显微组织控制

在钢轧辊局部缺陷冷焊焊缝中,研究了多元强碳化物元素和RE元素对碳化物数量、形态和基体组织的影响。结果表明,经Nb、Ti、V、Zr、RE的综合作用,促进了碳化物早期、大量弥散析出,抑制了导致脆化的沿柱状晶界的网状析出;由于C主要补固定在第二相,使其固溶态份额降低而导致奥氏体“贫C”,从而形成低碳板条马氏体而避免了韧性较差的高碳马氏体基体产生,显著提高了焊态韧性的冷焊抗裂性。     

冷轧工作辊局部冷焊焊缝中残余奥氏体对抗疲劳性的影响

在９Ｃｒ２Ｍｏ轧辊局部冷焊焊缝中,研究了焊缝服役后的疲劳现象与残余奥氏体（Ａｒ）数量、形态的关系。结果表明：块状Ａｒ是焊缝早期疲劳的主要原因;其疲劳机制是块状Ａｒ塑变切断破坏和高应力诱发相变孪晶。强碳化物形成元素与Ｃ符合定比规律后,固溶入基体的弱、非碳化物元素影响着Ａｒ的数量和形态。薄膜状Ａｒ与板条马氏体（Ｍｌ）形成的Ｍｌ／Ａｒ束,可显著地提高冷轧抗疲劳性。     

高速工具钢中碳化物的形态

<正> 在高速工具钢中存在着M6C、M2C、MC三种类型的初生碳化物。这些碳化物都是在凝固过程中从钢液中结晶出来,成为最终产品中的未溶碳化物残存在钢中,起着增加耐磨性、防止奥氏体晶粒粗化的作用。但是,这些碳化物的硬度均大于HV1500,几乎没有塑性,因而存在形态、粒度及其分布、相对量等对材料的机械性能都有极大的影响。其中具有Fe3(W,Mo)3C～Fe4(W,Mo)2C 成分的M6C 型碳化物在高速钢工具钢的初生碳化物中构成比例最大,必须在浇铸时尽量地进行细化。照片1(a)是SKH2(18W—4Cr—1V)     

合金工具钢9SiCr脱碳深度测定方法的研究

9SiCr 是国家标准“合金工具钢技术条件”(GB1299-77)中、推荐作为刃具使用的主要钢种之一。这种低合金工具钢具有较好的淬透性和抗回火性,有碳化物分布均匀、过热敏感性小等优点,但这个钢种含有     

高铬工具钢的锻造

合金工具钢在我国应用很广,目前使用最多的有Cr12、Crl2Mo、Cr12MoV和Crl2V,由于它们含铬量高达12％左右,因此,通称为高铭工具钢。高铬工具钢含有大量的合金元素和碳元素组成高硬度复杂碳化物。高合金的复杂碳化物很难溶解在奥氏体中,因此,不能用普通的热处理方法改善其性能,唯有借助锻造机械的力量,才能击碎这些复杂碳化物,使它均匀地分布     

时效硬化工具钢

时效硬化工具钢是近代兴起的一种工具材料,它和传统的用碳化物强化的工具钢有很大的区别。本文着重介绍了在合金相及强化机制方面具有代表性的时效硬化高速钢的成份、组织和性能,评述了有关铁-钨(钼)及铁-钨(钼)-钴镍系强化机制的研究成果,并作了一般性理论分析.     

钢结硬质合金的加工

<正> 前言钢结硬质合金(简称钢结合金)是以极硬的碳化物(TiC 或 WC)作硬质相,合金钢作粘结剂,用烧结方法制成的一种粉末冶金制品。它既具有硬质合金那种高硬度和高耐磨性,又象一般工具钢一样可进行机械加工。实践已证明,用这类合金所制的工模具,其使用寿命可成倍的提高。     

显微组织对热作工具钢韧性的影响

对经过不同冷却速度淬火并回火的AISI H13, H10, H19等热作工具钢的显微组织进行观察分析,探讨伴随冷却速度的降低上贝茵体等显微组织的变化规律,研究了上述热作工具钢的韧性与基体中微细碳化物的密度和残余碳化物粒度之间的关系。     

化学热处理工艺要领浅析(四)

一、化学气相沉积(CVD)十几年来,用化学气相沉积法在硬质合金、工具钢、模具钢等基础上建立的涂层,有碳化物,氪化物,碳氮化合物、氧化物、硼化物,硅化物和多层复合涂层等八大类。在六、七十种涂层中,国内外应用较广的是碳化钛和氮化钛涂层。1.碳化物涂层钛、钒、铬等碳化物层的气相沉积,通常以氢气     

BHW-35钢焊缝熔敷金属热处理脆化机理研究

用于高参数锅炉的BHW－35钢采用窄间隙埋孤焊，在焊后热处理后其焊缝冲击韧性大幅下降。利用扫描电镜（SEM）和透射电镜（TEM），对焊缝熔敷金属焊后热处理后的显微组织变化进行研究，找出其冲击韧性下降原因。结果表明：BHW－35钢焊缝焊态时组织为针状铁素体，在晶内有细小碳化物弥散分布；经焊后热处理后，针状铁素体变为块状，碳化物在晶界大量折出，导致晶界脆化和冲击韧性下降。     

Study on microstructure and mechanical properties of dissimilar steel joint developed using friction stir welding

In the present study, microstructure and mechanical properties of dissimilar weld of structural steel and ferritic stainless steel (FSS) plates of thickness 3 mm were investigated. The plates were butt welded by friction stir welding and defect-free welds were produced at a traverse speed of 20 mm/min and rotational speed of 508 rpm using a tungsten carbide tool. The weld joint consisted of alternate bands of both steels resembling an onion ring pattern. In the weld joint, six distinct regions were found including both the base metals. The stir zone of structural steel revealed refined grain structure of ferrite, pearlite, and martensite whereas in ferritic stainless side, highly refined ferritic grains with grain boundary martensite was observed and also confirmed by x-ray diffraction (XRD). The hardness of the weld joint varies from 186 to 572 HV. This scatter of hardness in stir zone is due to the presence of metal from both sides. The ultimate tensile and yield strengths of the transverse weld specimens was higher than the structural steel base metal whereas lower than the ferritic stainless steel, having fracture from structural steel side.     

Some investigations on microstructure and mechanical properties of submerged arc welded HSLA steel joints

This paper investigates the influence of the submerged arc welding (SAW) process parameters (welding current and welding speed) on the microstructure, hardness, and toughness of HSLA steel weld joints. Attempts have also been made to analyze the results on the basis of the heat input. The SAW process was used for the welding of 16 mm thick HSLA steel plates. The weld joints were prepared using comparatively high heat input (3.0 to 6.3 KJ/mm) by varying welding current (500–700 A) and welding speed (200–300 mm/min). Results showed that the increase in heat input coarsens the grain structure both in the weld metal and heat affected zone (HAZ). The hardness has been found to vary from the weld centre line to base metal and peak hardness was found in the HAZ. The hardness of the weld metal was largely uniform. The hardness reduced with the increase in welding current and reduction in welding speed (increasing heat input) while the toughness showed mixed trend. The increase in welding current from 500 A to 600 A at a given welding speed (200 mm/min or 300 mm/min) increased toughness and further increase in welding current up to 700 A lowered the toughness. Scanning electron microscopy of the fractured surfaces of impact test specimen was carried out to study the fracture modes. Electron probe micro analysis (EPMA) was carried out to investigate the variation in wt.% of different elements in the weld metal and HAZ.     

冷轧激光焊接DP780高铝双相带钢表面印迹产生原因

DP780高铝(铝质量分数在0.55%~0.70%)双相钢经热轧、头尾激光焊接、酸洗、冷轧后,其带钢表面出现印迹,通过显微组织、化学成分和硬度分析研究了印迹产生原因。结果表明:在DP780双相钢焊接过程中,焊缝金属中的铝元素发生氧化形成氧化铝,氧化铝未能在酸洗中有效清除;在冷轧时硬质氧化铝造成工作辊损伤,从而在带钢表面形成印迹。提高焊接速度、酸液浓度和酸洗温度能完全消除带钢表面印迹。     

12Cr2Mo1R钢焊条电弧焊焊接接头的性能

采用焊条电弧焊工艺用奥氏体A302焊条对12Cr2Mo1R钢进行焊接,焊后对焊接接头进行425℃保温370h的热处理;对焊接接头进行了显微组织观察、能谱分析、物相测定和高温拉伸、冲击试验。结果表明:焊缝区组织为奥氏体、δ铁素体和少量碳化物;焊接接头高温拉伸屈服强度比母材的大,焊缝区的冲击功比母材的低;在焊缝区产生了少量脆性碳化物(M23C6型)和铁-铬新相,造成焊缝区的脆性比母材的增大。     

硬质合金与碳钢电子束对接焊接头的显微组织

选用YG30硬质合金与45钢进行电子束对接焊复合试验，用扫描电镜、波长分散X射线谱仪对焊接接头显微组织进行了分析。结果表明：当电子束电流小、焊接速度慢时，焊接接头易形成有害的η相，η相分布于YG30／焊缝界面区域，并聚集长大，η相层厚度约10μm；焊接过程中硬质合金脱碳和铁向硬质合金迁移是叩相形成的主要原因。     

压力容器窄间隙埋弧焊热处理脆化机理研究

用于制造高参数压力容器的低合金高强度铜采用窄间隙埋弧焊,为了消除焊接残余应力,在焊后需对焊接接头进行热处理,其冲击韧性大幅下降。为探讨其脆化机理,选用BHW-35钢为母材,H10Mn2NiMoA镀铜焊丝和SJ101焊剂为填充材料,焊后热处理工艺为920℃正火＋620℃和560℃二次回火。利用扫描透射电镜,对焊缝熔敷金属焊态和焊后热处理的显微组织变化进行了研究。结果表明,低合金高强度钢焊缝焊态时组织为针状铁素体,在晶内有细小碳化物弥散分布;经焊后热处理,由于回复作用板条状组织变粗或消失,在晶界磷元素的偏聚和大量的碳化物在晶界析出导致其冲击韧性下降。窄间隙埋弧焊是一种优质高效的焊接方法,焊接效率高,节约焊材,解决了大厚度工件焊接的技术问题。     

Effect of welding heat input on fatigue life of quenched boron steel and FB steel lap joint

The effect of welding heat input on the fatigue life of a quenched boron steel and ferrite-bainite (FB) steel lap joint was investigated. Boron steel was quenched and welded with FB steel in heat input ranging from 0.29 to 0.67 kJ/mm. Boron, which can increase hardenability, affected the microstructure and hardness of the weld metal and heat affected zone (HAZ). The hardness of the weld metal and HAZ increased with decreasing welding heat input, and the high hardness of the weld metal and boron steel HAZ prevented the initiation of cracks in the stress concentration area around the bead. The bead width increased with increasing heat input, and the results of finite element method (FEM) showed that the maximum stress in the notch of the weld joint decreased when the bead width was increased. That is to say, the fatigue life increased when the weld joint had wider bead width. Finally, while the fatigue life was affected by the residual stress, the variation of the welding heat input used in this study had hardly any affect on the residual stress distribution.     

含钒高铬铸铁自保护金属芯堆焊焊丝的研制

研制了一种自保护金属芯堆焊药芯焊丝。堆焊过程飞溅小，焊缝成型美观。堆焊层组织为马氏体＋残余奥氏体＋碳化物硬质相。堆焊层硬度为HRC60，相对耐磨性为Q235钢的21倍。焊丝的熔滴过渡方式为典型的短路过渡。研究焊丝粉芯成分对焊丝的性能发现，石墨可以有效的降低飞溅，当粉芯中的石墨含量为3％时，堆焊过程中的飞溅率最低，此外增加粉芯中钒的含量，堆焊层的硬度和耐磨性上升。     

Virgo104 铸钢及焊接接头力学性能研究

对Virgo104钢的力学性能进行了检验,并研究了与之匹配的两种气保焊焊丝及一种焊条的焊接接头力学性能.试验结果表明,Virgo104钢中心与表面的力学性能基本一致,具有良好的强度与塑性匹配,而且具有优良的低温冲击韧度,特别是其高的Wp/Wi(约3.0)及高的侧向膨胀率(约15%),表明该钢具有优良的抗脆性断裂性能.焊缝金属及焊接接头具有良好的力学性能,其中HS367L焊丝的焊缝金属,在焊态下具有较高的塑性,预示出较高的抗焊接裂纹性能.