The Welding Instructions of Clad Plate

Range of Application

This technique can be applied to any clad metals in which the clad metal is stainless steel and the base metal is carbon steel or other lean alloy steel and also the whole thickness is bigger or equal to 4mm.

2.1 The principle of the selection of welding materials

2.1.1 The selection of composite materials should ensure that the content of alloying elements of the deposited metal is not lower than the lower limit specified in the standard of the composite material.

2.1.2 The electrode of the transition layer should be 25%Cr-13%Ni or 25%Cr-20%Ni to supplement the dilution of the base layer. The 25%-13%Ni-Mo type electrode should be used for the composite plate with molybdenum in the complex layer.

2.2 Commonly used stainless steel clad plate welding materials can be selected according to tables 2.2-1 and 2.2-2.

Table 2.2-1 commonly used stainless steel clad plate transition layer and multi layer welding material selection.

Table 2.2-2 Most commonly used welding materials for base metal of stainless clad plate

Pre-welding preparation

3.1 Blanking
Stainless steel composite steel plate cutting and groove processing as far as possible the use of mechanical processing method, the cutting surface should be smooth, when shearing machine cutting, the compound should be upward. Plasma cutting can also be used. When cutting, the upper layer is raised and the cut slag is not allowed to fall on the compound layer.

3.2 Groove processing and inspection
The groove form and size shall be specified according to the drawing design. If the design is not specified, reference can be made to drawing 3.2-1.
The principle of groove selection is to ensure that the welding quality is small, the fusionratio is small, and the operation is convenient.
The machining of the bevel is usually made of mechanical method. If plasma cutting and gas cutting are used to open the groove, the oxide layer on the surface of the composite must be removed.
The groove of D. should be checked for appearance without cracks and delamination, otherwiseit should be repaired.

3.3 Pre-welding cleaning
In the 20mm range of the slope and its sides, the surface cleaning is carried out by mechanical method and organic solvent, and the surface oil, rust, metal chips, oxide film and otherdirt are cleared, and the splash coating should be coated in the range of the 100mm range of the compound layer.

3.4 The assembly of welding parts
The A. assembly should be based on the complex layer, and its error should not be more than 1/2 of the thickness of the complex layer, and not more than 2mm. For the thickness of the complex layer, the amount of the wrong side is taken at a smaller thickness.
B.positioning welding should be welded to the base metal and the same welding material is applied to the base metal. Reference table 3.5-1 for welding of hand arc welding.

Table 3.4-1 Welding seam size in hand arc welding（mm）

Delta 0 is the thickness of the base

C. during the assembly process, it is strictly prohibited to weld the fixture on the complexlayer, and the work fixture should be welded on the side of the base.
The welding of one side of the D. layer is in accordance with the requirements of the designdrawings. When the design requires that the compound layer is welded on the base metal, the compound layer should be stripped first and the stainless steel bracket is welded on the base shell with the transition layer welding electrode. The weld surface is welded with the same welding electrode.

Welding

When the technical conditions of the product are required to evaluate the welding process,  the construction units must make the welding process evaluation according to the structural features and technical requirements of the products before the start of the construction,  and obtain the approval of the quality supervision department.

4.1 Welding Method
Manual welding, submerged arc welding and carbon dioxide gas shielded arc welding are recommended for welding at the grassroots level. The welding of the overlay and the overlayer is made of tungsten argon arc welding and manual arc welding, and other welding methods that can ensure the welding quality.

4.2 Welding Procedure
Welding should first weld the base, then weld the transition layer, and finally weld the layer (as shown in figure 4.2-1). When the conditions are restricted, the complex layer can be welded first, then the transition layer and the base can be welded. In this case, if the thickness of the composite plate is less than 10mm, the welding of the base can be directly selected as the same welding material with the transition layer. If the thickness of the composite plate is greater than 10mm, the welding thickness of the transition layer (the thickness of the transition layer) can be properly increased. The degree should be greater than or equal to 5mm), and finally carbon steel or low alloy welding base.

Welding of the base metal
The soldering line of the welding base must not touch or melt the composite material.When the substrate is first welded, the root or surface of the weld bead should be 1-2mm away from the composite interface. The residual height of the weld shall be in accordance with the relevant standards. Depending on the thickness of the substrate, steel type and structure,appropriate preheat treatment is necessary.
Welding of the transition layer
When welding the transition layer, we should minimize the fusion amount of base metal and reduce the fusion ratio under the premise of ensuring good fusion. For this reason, smaller diameter electrodes or welding wires and smaller welding line energy should be used. The thickness of the transition layer should not be less than 2mm.
Welding of the clad layer
In the welding clad layer, we should pay attention to protecting the surface of the compound layer, prevent the welding spatter from damage the complex layer surface, and do not take arc at random on the surface of the complex layer, welding Karan, ring and temporary support. The surface of the multiple layer weld should be smooth and smooth as far as possible. The joint height of butt weld is not more than 1.5mm.

5、Heat treatment after welding
5.1 the heat treatment after welding is carried out according to the design requirements.
5.25.2 containers, pipes, or components made with a stainless steel composite board are recommended to be carried out before the welding transition layer and heat treatment at the base of the base when the post weld heat treatment is required. The post weld heat treatment parameters of commonly used stainless steel composite panels are shown in table 4.3.2-1.

Table 4.3.2-1 Heat treatment parameters of common stainless steel clad plate after welding

Note：T indicates the total thickness of the stainless steel clad plate（mm）.

5.3 corrosion resistant stainless steel clad plate welded pipe should be washed and passivated on the surface of the weld.

6、Welding quality inspection
The welding quality inspection items of the stainless steel composite board generally include appearance inspection, nondestructive testing, mechanical performance test, pressure test, intercrystal corrosion tendency test and metallographic inspection. The inspection items for each product should be held according to the specification of product design drawings and technical conditions.

6.1 Apperance Inspection
a.The weld shape of A. is good and the size should meet the design requirements.
B.holes and slag inclusions, cracks and arcs should not be found on the weld and heat affected zone surfaces.
C.When the product design drawings and technical conditions are not clearly defined, the bite depth of the base side welds shall not be more than 0.5mm, and the length of the bite is not greater than 10% of the length of the weld, and no more than 100mm. There is no bite defect on one side of the compound.
6.2 when the technical condition of the product is required to evaluate the welding process,or to provide the performance of the welding test plate and the specification of the technical conditions, the mechanical performance test, the nondestructive flaw detection of the weld and the metallographic inspection should also be carried out.

7、Rework
When there are defects that are not allowed to be welded joints, defects should be removed and repaired according to the rework process requirements.