YG8硬质合金与42CRMO钢的真空钎焊及焊后热处理研究

YG8硬质合金与42CRMO钢的真空钎焊及焊后热处理研究 摘要 I摘 要 本文以铣刨机刀头为研究背景采用自行研制的CuMnNi钎料研究了YG8硬质合金与42CrMo钢的各种真空钎焊工艺参数如钎焊温度、钎缝宽度、中间层厚度等对钎焊接头组织和性能的影响并对焊后热处理进行了研究。 根据本实验中两种母材的特点设计出合适的钎料成分经熔炼、锻造、轧制出实验所需的钎料薄带。该钎料熔点范围在945?990?。该钎料对母材有良好的润湿性。随着钎焊温度升高润湿性越来越好温度高于1030?润湿角均小于6?。 Co往钢侧Fe往硬质合金侧长程扩散其中Co的扩散能力大于FeNi往硬质合金中的扩散量大于往钢中的扩散量Cu和Mn有部分扩散。在钎缝区两侧界面反应区均形成以FeCoNi为基的固溶体不仅实现了接头的良好冶金结合而且有利于接头残余应力释放。 最佳钎焊温度为1030?。当钎缝宽度在0.2mm时在此钎焊温度下接头抗弯强度值为444MPa。温度太低钎料流动性差元素扩散不充分不利于接头的冶金结合温度过高会导致钎料中Mn的严重挥发影响接头性能。 最佳钎缝宽度为0.3mm接头抗弯强度可以达到510MPa。间隙过小不利于液态钎料的流动填缝困难同时间隙过小钎缝松弛应力的能力较差接头性能较低。间隙过大毛细作用下降且钎焊过程中容易发生钎料流淌不能填满间隙同时间隙过大元素长程扩散困难在钎缝界面处冶金结合下降从而使接头性能下降。 添加不同厚度Ni中间层均不能提高接头抗弯强度反而使接头抗弯强度下降。其原因主要是固态中间层会强烈阻碍Co、Fe元素的长程扩散不利于接头的冶金结合。 焊后热处理实验表明淬火不仅可以起到强化钢的作用而且由于冷却过程中钢发生马氏体相变产生体积膨胀抵消了部分残余应力可明显提高接头抗弯强度。在1030?下钎焊钎缝宽度为0.2mm淬火前后接头抗弯强度值从444MPa提高到561MPa。 关键词真空钎焊CuMnNi钎料YG8硬质合金42CrMo钢钎缝宽度中间层焊后热处理 本文以铣刨机刀头为研究背景采用自行研制的CuMnNi钎料研究了YG8硬质合金与42CrMo钢的各种真空钎焊工艺参数如钎焊温度、钎缝宽度、中间层厚度等对钎焊接头组织和性能的影响并对焊后热处理以及真空钎焊的各个参数真空度、加热速率、保温温度及时间、钎焊保温时间、冷却速率、出炉温度进行较为系统的研究。 本课题在致力于研制新型钎料以及选择合适的钎焊方式的同时考虑到焊后热处理的理论可行性。淬火过程中由于钢发生马氏体相变而马氏体相变过程为体积膨胀过程淬火过程中马氏体相变导致的体积膨胀可以松弛硬质合金侧的残余拉应力。这为焊后热处理提供了理论上的可行性。 因此焊后淬火不仅可以起到强化钢的作用还可抵消部分残余热应力同时由于采用了钎焊与热处理的一体化工艺避免了二次加热既提高接头的综合机械性能又能节省能源提高生产率。 根据本实验中两种母材的特点设计出合适的钎料成分经熔炼、锻造、轧制出实验所需的钎料薄带。该钎料熔点范围在945?990?。该钎料对母材有良好的润湿性。随着钎焊温度升高润湿性越来越好温度高于1030?润湿角均小于6?。 在钎缝区存在着Co、Fe、Ni等元素的长程扩散 Co往钢侧Fe往硬质合金侧长程扩散其中Co的扩散能力大于FeNi往硬质合金中的扩散量大于往钢中的扩散量Cu和Mn有部分扩散。在钎缝区两侧界面反应区均形成以FeCoNi为基的固溶体不仅实现了接头的良好冶金结合而且有利于接头残余应力释放。 最佳钎焊温度为1030?。温度太低钎料流动性差元素扩散不充分不利于接头的冶金结合。温度过高会导致钎料中Mn的严重挥发改变接头钎料的成分使得熔点上升流动性变差33导致接头强度下降。 当钎缝宽度在0.2mm时在此钎焊温度下接头抗弯强度值为444MPa。温度太低钎料流动性差元素扩散不充分不利于接头的冶金结合温度过高会导致钎料 中Mn的严重挥发影响接头性能。 最佳钎缝宽度为0.3mm接头抗弯强度可以达到 510MPa。钎缝宽度为0.3mm时钎料具有较好的润湿性能较好地释放接头的残余应力 且具有良好的冶金结合。间隙过小不利于液态钎料的流动填缝困难且钎料对接头应 力的释放较差接头性能较低。间隙过大毛细作用下降钎焊过程中容易发生钎料流淌 难以填满钎缝间隙固溶体组织具有良好的塑性和强度间隙过大使得Fe、Co元素的长 程扩散困难在钎缝界面处冶金结合下降从而影响接头性能。 Ni中间层在某种程度上 可以松弛接头的残余应力但两侧母材中的Fe、Co元素很难穿过固态中间层进行扩散 从而弱化了接头的冶金结合不利于提高接头强度。在两个矛盾的因素综合作用下中 间层厚度为0.3mm时接头抗弯强度达到一峰值326MPa比不添加中间层厚度时的强 度峰值要低36。但总体而言添加Ni中间层不仅不能提高接头抗弯强度还会使其下降。 其原因主要是固态中间层会强烈阻碍Co、Fe元素的长程扩散不利于接头的冶金结 合。 长久以来由于硬质合金与钢的线膨胀系数差异大焊接残余应力较大为了减小残 余应力普遍认为钎焊后应进行缓慢冷却不能进行淬火等热处理操作。同时由于目前 普遍采用黄铜和银基钎料熔点较低不能与42CrMo钢的淬火温度相配匹。因此国内企 业生产类似产品一般不再进行焊后淬火处理。但是焊后不进行淬火处理42CrMo钢的 硬度较低耐磨性较差难以满足铣刨机刀具对钢体性能的要求。 焊后热处理实验表明 淬火不仅可以起到强化钢的作用而且由于冷却过程中钢发生马氏体相变产生体积膨 胀抵消了部分残余应力可明显提高接头抗弯强度。在1030?下钎焊钎缝宽度为 561MPa。 Under the research 0.2mm淬火前后接头抗弯强度值从444MPa提高到 background of milling machine head this issue has studied vacuum brazing of YG8/42CrMo steel in some process parameters such as brazing temperature、joint gap and interlayer as well as post-weld heat treatment and their effect on the property and structure of brazing joint. Self-developed CuMnNi alloy was chosen as filler metal. The various vacuum brazing parameters vacuum heating rate the temperature and time brazing insulation cooling rate temperature released were studied in detail also. Some effect was devoted into the development of new types of brazing material and the choice of a suitable way of brazing. At the same time the theoretical feasibility of post-weld heat treatment was taking into account. Martensitic transformation with its volume expansion during quenching process can lead to expansion of the size. Which can release the residual tensile stress of Carbide side This provides a theoretical possibility to post-weld heat treatment. So quenching after welding steel can not only to strengthen the steel but also to offset part of the residual thermal stress owing to the integration of the brazing and heat treatment process reheating was avoided joints mechanical properties was not only raised but also energy was saved and productivity increased. An excellent brazing filler composite was designed filler ribbon was got by melted、forged and rolled. It’s melting point ranged from 945?990?which has good wettability to YG8 and 42CrMo steel. The wettability gets better and better with the rising of temperature. Wetting angle on both YG8 and 42CrMo steel are less than 6?when temperature is higher than 1030?. Abstract IIAbstract Under the research background of milling machine head this issue has studied vacuum brazing of YG8/42CrMo steel in some process parameters such as brazing temperature、joint gap and interlayer as well as post-weld heat treatment and their effect on the property and structure of brazing joint. Self-developed CuMnNi alloy was chosen as filler metal. An excellent brazing filler composite was designed filler ribbon was got by melted、forged and rolled. It’s melting point ranged from 945?990which ha?s good wettability to YG8 and 42CrMo steel. The wettability get better and better with the rising of temperature. Wetting angle on both YG8 and 42CrMo steel are less than 6?when temperature is higher than 1030?. In the brazing joint Co diffused to steel and Fe diffused to hard alloy through a long-range. And the diffusion capacity of Co is stronger than Fe. The amount of Ni diffused to the hard alloy is more than to the steel. The diffusion of Cu and Mn is little. FeCoNi-based solution are formed at the interface of joint the formation of solid solution is not only beneficial to the joint metallurgical but also conducive to the releasion of residual stress. The optimum brazing temperature is 1030?. When the joint was brazed at 1030? and the joint gap is 0.3mm the bending strength of joints can reached a maximum with an average value of 444MPa. Fluidity of filler is poor and diffusion of elements is inadequate at lower temperature. At higher temperature manganese loss severely which would effected joint performance. The optimum joint gap is 1030?. The bending strength of joints can reached a maximum with an average value of 510MPa. If the gap was excessively small joint can’t relax residual stress well strength of joint is lower. When the gap oversized long-range spread of elements become difficult and interface metallurgical decline thus effect the joints performance. Add different thickness of Ni layer strength of joints can’t be improved but declined.The main reason is that the diffusion of alloy element is weakened which is not conducive to the metallurgy binding of brazing joint. The result of heat treatment after brazing showed that quenching can not only play the role of strengthening steel at the same time volume expansion produced in martensitic transformation can offset part of the residual stress during cooling process of steel which can significantly increase joint bending strength. When the width of brazing is 0.2mm and the temperature is 1030? the bending strength of joint increased from 444Mpa before quenching to 561Mpa after quenching. Abstract IIIKeywords: vacuum brazing CuMnNi brazing filler metal YG8 hard metal 42CrMo steel brazing gap interplayer post-weld heat treatment 元素很难穿 过固态中间层进行扩散从而弱化了接头的冶金结合不利于提高接头强度。在两个矛 盾的因素综合作用下中间层厚度为0.3mm时接头抗弯强度达到一峰值326MPa比不 添加中间层厚度时的强度峰值要低36。但总体而言添加Ni中间层不仅不能提高接头 抗弯强度还会使其下降。其原因主要是固态中间层会强烈阻碍Co、Fe元素的长程扩 散不利于接头的冶金结合。 长久以来由于硬质合金与钢的线膨胀系数差异大焊接残 余应力较大为了减小残余应力普遍认为钎焊后应进行缓慢冷却不能进行淬火等热处 理操作。同时由于目前普遍采用黄铜和银基钎料熔点较低不能与42CrMo钢的淬火温 度相配匹。因此国内企业生产类似产品一般不再进行焊后淬火处理。但是焊后不进 行淬火处理42CrMo钢的硬度较低耐磨性较差难以满足铣刨机刀具对钢体性能的要 求。 焊后热处理实验表明淬火不仅可以?鸬角炕 值淖饔枚 矣捎诶淙垂 讨懈址 ? 硎咸逑啾洳 寤 蛘偷窒 瞬糠植杏嘤α 擅飨蕴岣呓油房雇淝慷取 ,?030?下钎焊钎缝宽度为0.2mm淬火前后接头抗弯强度值从444MPa提高到 561MPa。 Under the research background of milling machine head this issue has studied vacuum brazing of YG8/42CrMo steel in some process parameters such as brazing temperature、joint gap and interlayer as well as post-weld heat treatment and their effect on the property and structure of brazing joint. Self-developed CuMnNi alloy was chosen as filler metal. The various vacuum brazing parameters vacuum heating rate the temperature and time brazing insulation cooling rate temperature released were studied in detail also. Some effect was devoted into the development of new types of brazing material and the choice of a suitable way of brazing. At the same time the theoretical feasibility of post-weld heat treatment was taking into account. Martensitic transformation with its volume expansion during quenching process can lead to expansion of the size. Which can release the residual tensile stress of Carbide side This provides a theoretical possibility to post-weld heat treatment. So quenching after welding steel can not only to strengthen the steel but also to offset part of the residual thermal stress owing to the integration of the brazing and heat treatment process reheating was avoided joints mechanical properties was not only raised but also energy was saved and productivity increased. An excellent brazing filler composite was designed filler ribbon was got by melted、forged and rolled. It’s melting point ranged from 945?990?which has good wettability to YG8 and 42CrMo steel. The wettability gets better and better with the rising of temperature. Wetting angle on both YG8 and 42CrMo steel are less than 6?when temperature is higher than 1030?. In the brazing joint Co diffused to steel and Fe diffused to hard alloy through a long-range. And the diffusion capacity of Co is stronger than Fe. The amount of Ni diffused to the hard alloy is more than to the steel. The diffusion of Cu and Mn is little. FeCoNi-based solution are formed at the interface of joint the formation of solid solution is not only beneficial to the joint metallurgical but also conducive to the releasion of residual stress. The optimum brazing temperature is 1030?. When the joint was brazed at 1030? and the joint gap is 0.3mm the bending strength of joints can reached a maximum with an average value of 444MPa. Fluidity of filler is poor and diffusion of elements is inadequate at lower temperature. At higher temperature manganese loss severely which would effected joint performance. The optimum joint gap is 1030?. The bending strength of joints can reached a maximum with an average value of 510MPa. If the gap was excessively small joint can’t relax residual stress well strength of joint is lower. When the gap oversized long-range spread of elements become difficult and interface metallurgical decline thus effect the joints performance. The residual stress of joints can be relaxed to some extent by Ni layer but Fe and Co on both sides of the matrix can’t diffuse through middle layer thereby weakening the joint metallurgical which is not conducive to improve the joint strength. In combination of two contradictory factors when the thickness of middle layer is 0.3 mm the joint bending strength reached a peak of 326 MPa lower 36 than it with no layer. Overall Add different thickness of Ni layer strength of joints can’t be improved but declined. The main reason is that the diffusion of alloy element is weakened which is not conducive to the metallurgy binding of brazing joint. The result of heat treatment after brazing showed that quenching can not only play the role of strengthening steel at the same time volume expansion produced in martensitic transformation can offset part of the residual stress during cooling process of steel which can significantly increase joint bending strength. When the width of brazing is 0.2mm and the temperature is 1030? the bending strength of joint increased from 444Mpa before quenching to 561Mpa after quenching. 论 文 独 创 性 声 明 本人声明所呈交的学位论文是我本人在导师指 导下进行的研究工作及取得的研究成果。尽我所知除了文中特别加以标注和致谢的 地方外论文中不包含其他人已经发表或撰写过的研究成果也不包含为获得江苏科技 大学或其它教育机构的学位或证书而使用过的材料。与我一同工作的同志对本研究 所做的任何贡献均已在论文中作了明确的说明并表示谢意。 学位论文作者签名 日 期 学 位 论 文 使 用 授 权 声 明 江苏科技大学有权保存本人所送交的学位论文的复印件和电子文稿可以将学位论文的全部或部分上网公布有权向国家有关部门或机构送交并授权其保存、上网公布本学位论文的复印件或电子文稿。本人电子文稿的内容和纸质论文的内容一致。除在保密期内的保密论文外允许论文被查阅和借阅。 研究生签名 导师签名 日 期 日 期 第一章 绪论 1第一章 绪 论 1.1课题背景 本课题来源于厂、矿主要针对铣刨机刀头展开。路面铣刨刀具是路面铣刨机中完成路面具体切削任务的重要功能部件。铣刨机刀具安装于铣刨滚筒表面刀座孔中铣刨滚筒带动刀座及刀具相对路面做旋转铣刨切削运动和直线进给运动。路面铣刨切削类似于金属切削加工中铣削的逆铣铣刀旋转方向与前进方向相反以减少切削阻力和冲击振动1。沥青砼路面材料硬度极不均匀其中石英Si02组织的结构最为致密硬度高达HRC67致使刀具在工作中承受强烈的冲击和表面摩擦2。 上述工矿条件要求铣刨机刀头具有很高的耐磨性以及较强的抗冲击和抗弯能力。目前最常用的材料为硬质合金。硬质合金具有高硬度、高强度、耐磨性、耐高温、抗腐蚀、抗氧化和膨胀系数小等一系列优点。目前已广泛应用于制造各种金属刀具矿山采掘石油钻井地质勘探工具以及各种模具量具和耐磨损机械零件3。但硬质合金价格比较昂贵它的塑性和冲击韧性较差。因此绝大多数硬质合金工具均采用将小块的硬质合金作为镶嵌件。固定于用工具钢等制造的工具的工作部位由工具钢等高强钢来承受冲击载荷并节省贵重的硬质合金降低工具成本。 硬质合金与钢的复合方法很多如机械复合、梯度硬质合金复合、熔焊和钎焊复合、扩散复合4、铸造复合等技术。其中钎焊技术以工艺简单、工件间连接精密、连接强度高、结果重复性好、接头尺寸及形状适应性广、相对成本较低、适合规模化生产、变形小等一系列优点成为将硬质合金连接到钢基体金属上的最成功方法之一。 常用的钎焊方法有火焰、感应、炉中、电阻、浸沾、真空等方法。硬质合金钎焊早期传统工艺技术采用氧气、乙炔火焰加热。该工艺特点是简单易行 适用于小批量生产但钎焊质量差 容易出现加热不均匀、焊缝充满度差、产品一致性差等 所以在我国90 年代初期大部分企业就基本不采用了。感应钎焊、炉中钎焊及电阻钎焊生产率高质量稳定。感应钎焊多采用高频.