不锈钢复合板过渡层焊接时存在的问题

    北京怡丰源达不锈钢装饰工程有限公司是集销售与设计、加工、制作、安装为一体的北京不锈钢加工厂。本公司在北京不锈钢加工、不锈钢工程上始终坚持以人为本、质量兴业、用户至上的服务宗旨，以独到的设计风格、精良的施工质量、规范的工程监控体系、
     不锈钢复合板焊接，应将基层和复层分开焊接，基层与复层交界处应焊接过渡层。基层焊接和复层焊接属于同种焊接，工艺比较成熟。过渡层焊接属于异种钢焊接，也是不锈钢复合板焊接的关键。基层与复层成分及性能差异较大，因此控制好过渡层的焊接是获得高质量接头的关键。
   不锈钢复合板过渡层焊接时主要存在的问题：
  （1）过渡层 当采用不锈作填充金属时，碳钢母材和填充材料成分相差悬殊。由于碳钢一侧液态金属温度较低、流动性较差，不能充分相互混合，所以靠近熔合线碳钢成分所占比例越大，被稀释得就越严重，这部分被稀释的焊缝金属称为过渡层，它在碳钢和不锈钢焊缝之间会形成马氏体。当马氏体区较宽时，会显著降低接头韧性，使用过程中出现脆性破坏。因而要求冲击韧度较高时，选用高镍填充金属。
  （2）焊缝金属的稀释 由于基层碳钢不含合金元素Cr、Ni，所以熔化时对焊缝金属中合金元素Cr、Ni有稀释作用，使焊缝中奥氏体形成元素Cr、Ni含量减少，焊缝金属中会产生马氏体淬硬组织，易产生裂纹，从而恶化接头质量。因此，焊接过渡层时，应使用含铬、镍量较多的焊接材料，使之即使受到基层的稀释，也不会产生马氏体淬硬组织。同时采用合适的焊接方法和焊接工艺，减小基层一侧熔深和焊缝的稀释。
  （3）焊接接头高应力状态 由于碳钢与不锈钢线胀系数、热导率不同，在焊接高温下会产生热应力。同时焊接接头在交变温度条件下工作时，容易形成热疲劳裂纹。因而焊后热处理消除焊接应力是不可能的，可选用线胀系数与碳钢接近且塑性好的高镍基焊条焊接，使热应力集中在不锈钢一侧熔合线处，通过不锈钢的塑性变形，减小热应力及热疲劳应力的不利影响。

  （4）扩散层 基层碳钢含碳量高、合金元素含量少，而不锈钢相反，在熔合线两侧形成浓度差。焊接复合钢板时，碳从碳钢向不锈钢焊缝扩散，结果在熔合线碳钢一侧形成脱碳层而软化，在不锈钢焊缝一层形成增碳层而硬化。扩散层随温度增高和高温停留时间加长而增大。由于熔合线两侧金属性能相差悬殊，接头受力可能引起应力集中，降低接头的高温强度和塑性，因而扩散层是不锈钢复合板焊接的薄弱环节。文章来源：（http://www.yfyd360.com）

 常见的问题：
1、不锈钢复合板焊接时，可不可以先焊复层，再焊接过渡层，最后采用基层焊材焊接基层？为什麽？

基层一般是不锈钢，复层是碳钢，先焊了复层也就是最外层，怎么焊里面呢，而且你说的还是小口径。

2、 不锈钢的焊接方法有那几种呢? 又是否一定要用不锈钢作为焊材呢?

不锈钢的焊接方法很多，主要有：

    手工电弧焊

    手工氩弧焊

    自动氩弧焊

    熔化极惰性气体保护焊

    埋弧焊

    等离子弧焊

    激光焊等
Beijing Yi Feng Yuan Da stainless steel decoration Engineering Co., Ltd. is a set sales and design, processing, production, installation as one of Beijing's stainless steel processing factory. The company in Beijing stainless steel processing, stainless steel works always adhere to people-oriented, the quality of Societe Generale, customer supreme principle of service, with unique design style, excellent construction quality, standardize project supervision system,
Stainless steel clad plate shall be welded with the base layer and clad layer separately, and the transition layer should be welded at the junction of the base layer and the clad layer. The base layer and clad layer are the same kind of welding, and the process is more mature. The transition layer welding is a welding of dissimilar steel, which is the key of the welding of stainless steel clad plate. At the basic level, the composition and performance of the compound layer is large, so the welding of the transition layer is the key to obtain the high quality joint.
Main problems in welding of stainless steel clad plate:
(1) when the transition layer is filled with stainless steel, the carbon steel base material and the filling material composition differ greatly. Due to the low carbon steel by the side of the liquid metal temperature, poor liquidity cannot fully mixed with each other so close to the larger proportion of the fusion line carbon composition, was diluted to the more serious, this part of the diluted weld metal known as the transition layer, it between the carbon steel and stainless steel weld will martensite formation. When the martensite region is relatively wide, it will significantly reduce the joint toughness, the use of brittle failure. When the impact toughness is high, the high nickel filled metal is used.
(2) of the weld metal dilution due to non base carbon steel alloying elements Cr, Ni, so melting on the weld metal alloy elements Cr and Ni with dilution effect, make weld Austenite Formation elements (Cr, Ni content decreases, the weld metal will produce martensite hardened tissue, easy to produce crack, which deteriorates the quality of joints. Therefore, welding transition layer should be use more containing chromium and nickel welding material, even by the grassroots of dilution, also won't produce martensite hardened tissue. At the same time, the suitable welding method and welding technology is adopted to reduce the depth of the base side and the dilution of the weld.
(3) the high stress state of welded joints is due to the difference of the expansion coefficient and thermal conductivity between the carbon steel and the stainless steel, and the thermal stress will be produced at high temperature. At the same time, the thermal fatigue crack is easily formed when the welding joint is working under the condition of alternating temperature. And post weld heat treatment to eliminate welding stress force is not possible, can choose linear expansion coefficient and carbon steel and close to the plastic of high nickel base welding rod, the thermal stress concentration in the stainless steel side near the fusion line, through stainless steel plastic deformation and reduce the heat should be harmful effects of stress and thermal fatigue stress.
(4) the carbon content of the carbon content in the base of the diffusion layer is high, the content of the alloy element is little, but the stainless steel is opposite, and the concentration difference is formed on the two sides of the fusion line. Composite plate welding, carbon from carbon steel to stainless steel weld diffusion. The results in one side of the line of fusion carbon steel formation decarburized layer and softening, in stainless steel weld layer formation of carburizing and hardening. The diffusion layer increases with the increase of the temperature and the residence time of the high temperature. Due to the poor performance of the two sides of the fusion line, the stress concentration of the joint can be caused by the stress concentration, and the high temperature strength and plasticity of the joint are reduced, so the diffusion layer is the weak link of the welding of the stainless steel clad plate. Article source: (http://www.yfyd360.com)
Common problems:
1, welding of stainless steel clad plate, can't weld cladding, welding transition layer. Finally, the basic welding welding base? Why?
Basic level is generally stainless steel, clad is carbon steel, the first welding layer is the most outer layer, how to weld it, and you say or small caliber.
What kinds of welding methods, 2 stainless steel? Whether must use stainless steel as a welding material?
There are many welding methods for stainless steel:
Manual arc welding
Manual argon arc welding
Automatic argon arc welding
Inert gas shielded arc welding
submerged arc welding
Plasma arc welding
Laser welding