Q. What is Clad plate and overlay welding?
Strip back cladding on clad plate a minimum of 5 mm (3/16") from the edges of weld preparation before welding on the backing plate. Strip back shall be verified by etching. Weld the backing plate with matching electrodes so that the weld on the clad side is flush with the backing plate surface. Deposited ferritic weld metal must not contact the austenitic or high chromium steel cladding. For welded seams in clad material, use weld filler metals selected from the following table. Check for the alloy elements of the cladding weld, indicated in the table, using a proven quantitative analytical technique.
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Cladding Materials
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Weld Filler Metals
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Alloy Elements to be Analyzed
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13-Cr, Type 410S or 405 Design Temperature <316°C (600ºF)
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Type 309L
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None
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13-Cr, Type 410S or 405 Design Temperature >316°C (600oF)
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ENiCrFe-2, ENiCrFe-3, ERNiCr-3
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None
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Austenitic Stainless Steels Types 304, 304L, 316, 316L, 321, 347
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1st layer - Type 309L
2nd layer - matching electrode
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C, Cr
Ni, Mo, Cb, as applicable
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Monel 400
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ENiCu-7, ERNiCu-7
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Ni, Fe, Cu
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The Chemical analysis must meet the minimum requirements of the SFA Specification for the welding electrode being used, at a depth of the specified cladding thickness for the finished deposit surface. Make an analysis of each procedure and each circumferential seam. Make an analysis of one seam from each shell course and one seam from each head. If any weld is deficient, check all welds. Submit corrective action proposal to the OWNER for review.
When alloy overlay protection is specified, make the depth of the required composition to overlay 2.4 mm (3/32") minimum. Weld overlay shall consist of at least two layers. For austenitic stainless steel overlay, use Type 309L filler metal for the first layer. Use matching electrode for the subsequent layer(s).
Certain welding procedures may be capable of attaining the required thickness and chemical composition with one layer. Obtain prior approval for use of a one layer technique.
Check the chemical composition of the specified overlay of production welds using a proven quantitative analytical technique. Analyze for the major alloying elements, including carbon to establish that the overlay meets the specified composition at a depth of the specified overlay thickness from the finished deposit surface. Make one analysis of each procedure and one analysis of each shell course and each head.
When the P-3 thorough P-5 chromium-molybdenum steels are overlaid with austenitic stainless steel for hydrogen service, the Seller shall perform tests to show that the weld overlay procedure produces an overlay that is resistant to hydrogen disbonding. The results of the tests shall be submitted with the weld overlay WPS and PQR.