Application of Electroslag Welding for large order
Kremsmueller has manufactured and delivered equipment for a customer in the petrochemical industry using the ESW (Electroslag Welding) process.
Electroslag strip cladding (ESW): What is it and how does it work?
ESW is a special submerged arc welding process. “The process is used to increase the durability or service life of a component,” explains Daniel I., Head of the Welding and Testing Technology Department. ESW enables a protective layer to be applied to a carrier material quickly and efficiently. The base material is usually cheaper than the high-alloy protective coating. The alternative would be to manufacture the component entirely from the high-alloy material. “However, this variant would cost many times more,” says the welding expert.
In electroslag strip cladding, a strip material, usually made of stainless steel or nickel alloy, and a special powder mixture are melted using an electric arc and applied to the workpiece. The slag acts as a heat source and shielding gas.
Procedure for the apparatus
The major challenge, in addition to selecting the right strip/flux combination, was to determine the correct welding parameters and component shrinkage due to the high heat input. Different welding samples were also created for the three devices in order to determine the optimum parameters. Flanges, for example, were deliberately made larger in order to compensate for the shrinkage caused by welding.
From tests to qualification
“The path to qualification of the ESW process involved several steps to ensure safe and correct application,” explains the welding expert. The welders underwent special training that included both theoretical and practical content. After the training, they had to take a certification test in the presence of TÜV to confirm their knowledge and skills.
To qualify the welding process, test pieces were welded and then subjected to a comprehensive destructive test. The fulfillment of the mechanical/technological values and corrosion resistance were confirmed by the TÜV.
After welding, various non-destructive testing procedures such as visual inspection, surface crack testing, ultrasonic testing and PMI testing (Positive Material Identification) are required. “These tests ensure that the weld seams meet the required quality standards,” explains Daniel I.
Advantages and application examples of ESW
ESW offers cost advantages, a high deposition rate and low mixing with the base material, which makes it attractive for numerous industrial applications. With strip cladding, layers of 3 to 5 mm can be applied with only 15 to 20 % mixing. This means that the desired chemical composition of the surface can often be achieved after just one or two layers.
One example of the use of ESW, as with our equipment, is in the petrochemical industry, where it is used to improve the corrosion protection of pressure vessels.
ESW is also used in the oil and gas industry, for example to protect valves and pumps against wear.
Limitations of ESW
Despite its many advantages, ESW also has some limitations, such as material compatibility, the thickness of the cladding and geometric limits. These factors should be taken into account when planning and implementing ESW projects in order to achieve the best possible results.
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