【作者】 王海涛；

【导师】 杨春利；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2007， 硕士

【摘要】 铜合金堆敷层在兵器制造业上应用广泛。本文利用TIG堆焊方法在35CrMnSiA钢基体表面堆敷Hs201铜合金。在分析堆焊温度场分布、焊接工艺对温度场的影响及在电弧作用下堆敷层与基体熔池流动规律的基础上,主要对铜合金中泛铁的分布、形态的发展演变以及泛铁量规律进行了系统的研究。通过分析焊接传热过程,采用焊后堆敷层几何参数建立实体模型,利用高斯面热源和堆敷层体热源结合的复合热源作为热源模型,编写用户子程序实现热源摆动运动,模拟了不同工艺下的焊接温度场。研究结果表明:基体内部各点热循环最高温度、冷却速度随着距界面距离增加而减小;相同焊接电流时,摆动焊基体界面处热循环最高温度低于单道焊,冷却速度也小于单道焊;背部水冷焊接时,基体与堆敷层的冷却速度大大提高。通过实测值对模拟结果进行验证,发现在水冷焊接时基体表面处最高温度有较大误差,其余结果吻合较好。利用温度场分析获得的结果并结合电弧压力测量结果,研究堆敷层与基体熔池内液相的流动规律。研究结果表明:在假设前提下,不论是单一流场还是复合流场都会在很短的时间内达到稳定;在双相流场内,熔化基体从熔池底部向堆敷层两侧运动,液态铜合金由堆敷层顶部进入基体熔池。在流动过程中,接近熔池底部液相的流动速度较小,而堆敷层顶部流动速度较大。通过光学显微镜、扫描电镜、能谱分析和X-射线衍射等方法对界面区和堆敷层合金进行分析,利用温度场及熔池流场结果解释堆敷层中泛铁的分布、形态的演变过程。结果表明:在电弧压力的作用下,熔化基体流向堆敷层两侧,并在那里率先凝固形成泛铁;液态铜合金流入熔池,因此在堆敷层中心与熔池中心泛铁较少。随着焊接电流的增大,泛铁形态由最初的无可见泛铁(I<270A)发展到细小的颗粒状、类树枝状泛铁(I=270A),再发展到大块球状泛铁(I=300A),最后发展到Cu/Fe界面模糊,堆敷层内Cu、Fe相互包覆(I=330A)。通过EDXA方法测量堆敷层内泛铁量,建立泛铁量与焊接电流关系模型。论文最后讨论了控制泛铁量因素,结果表明:在270A时采用背部水冷的方法,泛铁量比空冷焊接时降低了40%;采用热丝焊接方法泛铁量降低了8.6%。更多还原

【Abstract】 Copper cladding layer has been widely used in field of weapons manufacturing. In this paper, a cladding of Hs201 was cladded on the surface of 35CrMnSiA steel substrate by means of tungsten inert gas (TIG) cladding. On basis of analyzing the temperature field, the influence of processing condition on temperature field, and the law of flow in the cladding layer and the molten pool under the effect of TIG-arc, distribution and concentration of Fe in the copper alloy cladding layer, the evolution of the morphology of Fe in the copper layer, and the content of Fe were studied primarily and systematically.Based on the comprehensive analyses of heat transfer behavior in cladding process, a entity model was presented by using the physical dimensions of cladding layers, the heat source was composed of a segment column heat source and a Gaussian distribution surface heat source, the weaving movement of heat source was achieved by user’s defined functions, and temperature fields under different cladding process were simulated. The results showed that the peak temperatures of weld thermal cycle decreased alone with the increasing of the distance from the interface in the steel substrate, cooling velocity also decreased; the peak temperatures of weld thermal cycle at interface is lower in weaving welding than single-pass welding at the same cladding current, the cooling velocity is also lower in weaving welding; the cooling velocity of cladding layer and the steel substrate increased greatly with water cooling to the back of the substrate; compared the results with the experimental data, there was a rather large error at the peak temperature at the interface in cladding on water cooling substrate. The other results obtained by simulation were in good agreement with the experimental ones.Using the results obtained from temperature fields analyze and from the arc pressure test, the law of flowing liquid in cladding layer and the molten pool in substrate. Results showed that following the presumption the paper given, either single phase flow field or double phase flow field became stable in a very short time; in double phase flow field molten steel at the bottom of the molten pool flowed to both sides of the cladding layer, Molten copper alloy at the top of the cladding layer flowed to molten pool. In flow field, rate of flow near the molten bottom was low, but it is high at the top of the cladding layer.The interface and the cladding layer were analyzed by means of optical microscope, SEM, EDXA, and XRD, and the evolution of the distribution and concentration of Fe, the morphology of Fe in the cladding layer was studied with the calculated results. The results showed molten steel was taken out of the molten pool to both sides of the cladding layer, and solidified there; molten copper alloy flowed into the molten pool so that there is little Fe in the middle of the cladding layer and the molten pool. Alone with increasing of cladding current, the morphology of Fe in cladding layer evolved from invisible Fe (I<270A) to fine grain or arborization (I<270A), and to block Fe (I=300A), and finally the interface of Cu/Fe became blurred, molten copper alloy and steel contained each other (I=300A). The content of Fe in cladding layer measured by EDXA, and the model on the relationship between the content of Fe and cladding current was built.At last the factors which could restrain the transfer of Fe were investigated, results show that Fe content decreased by 40% on a water cooling substrate when cladding current was 270A; at the same current, Fe content decreased by 8.6% with hot filler wire.更多还原