熔合焊接是在用于制备接头或任何其他动作之前，基材通常被加热熔化的地方。在熔焊过程中，主要特征之一是缺少填充材料。通常会添加填充材料来增加接合强度或用于其他目的。在熔焊工艺的情况下，不存在这样的填料，并且焊接操作被称为自熔焊接。熔焊状态焊接的一些形式是氧 – 气燃气焊接，电弧焊接和电阻焊接。氧气燃料焊接通常是将金属板与零件的切割和分离混合在一起。这里所用的混合物是氧气和乙炔，与通常的熔化焊接状态不同，填料可以用作例外（Li等人，2008）。这里使用的填充物通常是模仿焊接过程的填充物。火焰是由填料产生的，这使得它是一个非常经济和多功能的使用过程。它是利用低产量或用于维修工作。另一方面，弧焊形式的熔焊被认为是利用电弧的熔焊。电弧过程增加了焊接接头的强度。这是一个有利的汽车机械工程的联合技术。填充金属在这里再次使用，但只是因为它增加了正在制造的接头的强度。用电弧产生电弧，熔化的焊缝将凝固。电阻焊接不像电弧焊接那样普遍，并且是依靠热和压力技术来实现焊接的电阻焊接。这里使用电阻来控制界面处的电流，因此在这里不需要使用填充物。
Fusion welding is where the base material is usually heated to melt before it is used for preparation of joint or any other action. In the case of the fusion welding process, one of the main characteristics is the absence of the filler material. Usually a filler material would be added to increase the strength of the joint or for other purposes. In the case of the fusion welding process such a filler is absent and the weld operation is termed as an autogenous weld. Some of the forms of fusion state welding are oxy-fuel gas welding, arc welding and resistance welding. Oxy fuel welding is usually done as a separate mix of cutting and separation of metal plates to parts. Here the mix used is oxygen and acetylene and unlike the usual state of fusion welding a filler can be used as an exception (Li et al., 2008). The filler which is used here is usually one that is seen to imitate the weld process. The flame is produced by the filler and this makes it a very economical and versatile process to use. It is made use of low quantity production or for the use of repair jobs. On the other hand, the fusion welding in the form of arc welding is seen to be one that makes use of the electric arc. The electric arc process adds to the strength of the weld joint. This was a favourable joint technique in auto mechanic works. Filler metal is once again used here but only as it adds to the strength of the joint that is being made. With an electrode of creating an arc, the molten weld will solidify. The Resistance welding is not as commonly used as the arc welding and is one that relies on heat and pressure techniques to achieve the weld. Here an electrical resistance is made use of in order to control current flow at interface and hence it is not required to make use of a filler here.