Welding process for stainless steel clad plate

1.Use of
This process is suitable for a variety of stainless steel composite, low-carbon steel or low alloy steel as the substrate thickness is greater than or equal to 4mm stainless steel clad plate welding.
2.1Welding material selection principles
2.1.1 Stratified material selection should ensure that the deposited metal alloy element content of not less than the lower limit of the stratified material standards.
2.1.2 Transition layer of the electrode should choose the 25% Cr-13% Ni-type or 25% Cr-20% Ni type to complement the primary dilution stratified complex layer containing molybdenum stainless steel composite panels, should be 25% -13% Ni-Mo electrode.
2.2 Commonly used in stainless steel clad plate welding material can be Table 2.2-1,2.2-2 selected.
Table 2.2-1 commonly used stainless steel composite plate transition layer and multiple layer welding material selection

Table 2.2-2 commonly used stainless steel clad plate grass-roots welding material selection

1.Preparation before welding
3.1 Cutting
Cutting and beveling of stainless steel composite plate as far as possible the method of machining, the cutting surface should be smooth, the use of cutting shears, double layer should be facing up. Can also be used for plasma cutting, cutting stratified upward, prohibited the cutting slag falls stratified.
3.2 Processing and inspection of the groove
1.Form and size of the groove by drawing the design requirements, such as the design is not clearly defined, and may refer to Figure 3.2-1 selection.
2.Groove selection principles: to ensure that the quality of welding filler metal fusion than the small, easy to operate.
3.The groove processing is generally made ​​of mechanical methods. Plasma cutting, gas cutting and other methods to open the system groove, you must remove the oxide layer of the composite surface
d. The groove processing after visual inspection, no cracks and layered, otherwise it should be repaired.
3.3Weld before the clean-up
Mechanical means within the groove each side of 20mm range and organic solvents for surface cleaning to remove surface oil, rust, metal shavings, the oxide film and other dirt, splash paint from the groove of the stratified 100mm range should be painted.
3.4 Weldment assembly
a.Assembly should be stratified for the baseline, the wrong side should not be greater than half of the thickness of the stratified, no larger than 2mm, take the wrong side of the volume for the complex thickness, the smaller the thickness of the stratified
b.Tack welding should be welded on the primary parent material, and using the same welding materials and welding the base metal.

Manual arc welding positioning weld Refer to Table 3.5-1

δ0Thickness of Base

(c) in the assembly process is strictly forbidden welders stratified fixtures, tools and clamps should be welded at the grassroots side.
(d) the stratified side of the attachment welding to meet the requirements of design drawings, design requirements stratified measured attachment weld metal at the grass-roots level should be stratified first part of the peel, the use of the transition layer electrode welding stainless steel bracket at the grassroots level shell body, the weld surface welding stratified electrode welding.
Welding
When the product technical conditions for the welding procedure qualification required by the construction unit in the pre-construction based on the structural characteristics of the product and technical requirements to develop welding procedure qualification, and have achieved the recognition of the quality supervision department.
4.1 welding method
The primary welding manual arc welding, submerged arc, and carbon dioxide gas shielded arc welding is recommended. Stratified and over-layer welding, gas tungsten arc welding and manual arc welding, can be applied to other welding methods to ensure the welding quality.
4.2 welding procedures
Welding welding are advised to grass-roots, and then welding the transition layer, and finally welded stratified (as shown in Figure 4.2-1). When conditions are restricted, the first welding clad welding of buffer layer and grass-roots level, in this case, if the thickness of the composite plate is less than 10mm, the welding of the grass-roots level can be directly used with the same buffer layer of welding materials, if the composite plate thickness greater than 10mm, this time may be appropriate to increase the welding thickness of the buffer layer (buffer layer thickness of the welding should be greater than or equal to 5mm), the final carbon or low alloy welding the grassroots level.

Welding at the grass-roots level
Welding the primary weld shall not be touched and melted composites, the first welding substrate, the root of the weld bead or surface composite interface should be from the 1-2mm. The weld reinforcement shall comply with the provisions of the relevant standard. As the substrate thickness, steel, and structural factors can be used, if necessary, appropriate warm-up.
Transition layer welding
When welding the transition layer to ensure good fusion under the premise of minimizing the melting of the substrate metal into lower fusion ratio. This should be a welding rod or wire of smaller diameter and smaller welding energy. The thickness of the transition layer should be not less than 2mm.
Complex layer of welding
Welding stratified, pay attention to protect the surface of stratified to prevent weld spatter damage the surface of stratified, not the surface of stratified random arc welding Karan, rings and falsework. Clad weld surface as far as possible remain flat with the surface of the stratified fairing. Butt weld reinforcement not more than 1.5mm
5, post weld heat treatment
5.1 post-weld heat treatment according to the design implementation.
5.2 containers manufactured with stainless steel clad plate, pipe or components, when the need for post-weld heat treatment is recommended before in the welding of buffer layer according to the grassroots level requires heat treatment heating temperature. Commonly used stainless steel clad plate weld heat treatment parameters are shown in Table 4.3.2-1.
Table 4.3.2-1 commonly used stainless steel clad plate weld heat treatment parameters

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

5.3 corrosion resistance requirements of the container of stainless steel clad plate welded pipes, clad weld surface passivation pickling.
6, welding quality inspection
Components of stainless steel clad plate welding quality test items generally includes visual inspection, nondestructive testing, mechanical test, pressure test, intergranular corrosion tendency tests and metallographic examination, the test items of each product should be product design drawings and technical conditions regulations.
6.1 Appearance inspection
(a) weld shape, size should meet the design requirements.
(b) the surface of the weld and heat affected zone may not have pores, slag inclusions, cracks, craters and other defects.
(c) when no express provision in the product design drawings and technical conditions, the grass-roots side of the weld depth of undercut shall not be greater than 0.5mm, the length of the undercut shall not be greater than 10% of the total length of the weld, and shall not be greater than 100mm. Stratified side shall not be undercut defects.
6.2 product technical conditions for the welding procedure qualification, or requirement to provide performance and technical requirements of product welding test plate, but also for mechanical testing, nondestructive testing of welds, metallographic examination.
7, rework
When found that welded joints are not allowed in the defect, the defect should be clear clean, according to relevant repair process requirements for repair.