dissimilar metal welding

Dissimilar metal welding  

Dissimilar metal welding 

Dissimilar metal welding is termed as a joining process with two different materials together. 

dissimilar welding is a process in which two metals with different chemical compositions or properties are joined together.
In fact, two metals with the same name can be welded together, but if they have different chemical compositions and properties, classified as dissimilar metals. In this process, lots of factors need to be discussed because each joint of dissimilar metal is a special case and both metallurgical and design factors, must be viewed in terms of how the welding joint will be done under specific conditions.
                 The dissimilar metal welding process is widely used in many industrial applications for both technical and economic reasons. The adoption of this method provides the possibilities for the flexible design of the product using each material efficiently.

Metallurgical factor 

In dissimilar metal welding, the metallurgy of both base metal and weld metals, are an important factor and must be taken into account because the weld metal is a composite of the filler metal deposited and the fused base metals, the third metal may be actually involved also as a filler metal.
For a good dissimilar metal welded joint, the following factors should be considered:

• Thermal Expansion
• Metallurgical stability
• Corrosion 

Adoptable Welding processes for Dissimilar metal welding  

Basically, a sound dissimilar weld getting by:

 Fusion welding process 

Fusion welding is an important process used in the manufacture of modern boilers where the ingredients are joined by the formation of a molten pool of mats between them and quality welds are easily produced with high levels of continuity.

There are many choices are along with fusion welding .common fusion welding processes are as follows:

• Shielded metal arc welding
• Gas tungsten arc welding
• Gas metal arc welding
• Submerged arc welding
• resistance welding process
• electron beam welding 

Other welding processes

For high density using plasma arc, electron beam and laser beam welding are also used for joining dissimilar joints. Several other welding methods are also available with less difficulty for producing dissimilar metal welds like:

Ultrasonic welding process, Friction welding process, Resistance and diffusion welding as well as brazing and soldering process.

Brazing is of great importance for joining diffusion metals because in good behavior,

VARIOUS DISSIMILAR METALS WELDING COMBINATIONS

     
 For the full description, you can download it from here, the password for the document is "theweldings"

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Electrodes and filler wires for Dissimilar metal welding 

As per AWS some common welding electrodes and filler wires details are as follows:

Sr No	Material	P No	Base Metal	Filler Wire	Electrode
5	Alloy Steel	11-4	SA 335 P11	ER-80S-B2	E-8018-B2
		22-5	SA 335 P22	ER-90S-B3	E-9018-B3
6	Incoloy	45/5	SB 407 800 /            SA 335 P22	ER-NiCu-3	E-NiCrFe-2
7	Carbon Steel / Alloy Steel	1/8	SA 106 Gr B /              A 312 TP 304L	ER-309L	E-309L-16
8	Monel 400	42	Monel 400 SB 165	ER-NiCu-7	E-NiCu-7
9	LTCS / SS	1/8	SA 516 Gr 70 /        SA 240 TP 304	ER-309	E-309-16
11	Incoloy 800H	45/45	SB 407 800H	ER-NiCr-3	ENiCr-3
				ER-NiCr-3	E-NiCrFe-2
12	Alloy Steel P11 / Stainless Steel 304H	4/8	A 335 P11 /            A312 TP 304H	ER-NiCr-3	E-NiCrFe-2
13	Carbon Steel / Stainless Steel 304H	1/8	A 106 Gr B /         A312 TP 304H		E-309
14	Monel 400 /  Carbon Steel	42/1	SB 165 / A 106 Gr B	ER-NiCu-7
15	Incoloy / CS	45/1	B 407 800, 800H /    A 106 Gr B	ER-NiCr-3	E-NiCrFe-2
16	Alloy Steel P22 / CS	5/1	A 335 P22 /        A106 Gr B	ER-90SB3	E-9018-B3

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