Welded pipe to do what is good to do not leave marks, alloy steel in the welding before the attention to what?

DataTime:[2016-4-4]

Stainless steel welded pipe still need polishing, if they are not complicated structure can be used grinder type, handheld artifacts, efficiency will be higher. If you can't use grinder type, can only use handheld grinding machine.
Can use the net, stainless steel welding spot method of use:
Apply a suitable amount of stainless steel welding spot net to the stainless steel surface to be processed, 1 ~ 2 mm thickness, maintain 5-30 minutes or longer (by dirt, sheet material and processing request), had better use the scrub brush a few times of treatment process, surface scale, rust, completely clean, better (lime, or caustic) rinse with clear water, avoid rust. Use or not use experience for the first time, must be small first trial satisfied after heavy use.
Alloy steel has good resistance to high temperature oxidation and organizational stability, high temperature strength. But its poor weldability, hardening tendency, in the process of welding seam and heat affected zone may appear some problems as follows:
(1) after welding in the welding seam and heat affected zone of hard and brittle hardening organization, if the internal stress is larger, can appear cold crack, toughness, plasticity decreases.
(2) has a tendency to arc crater crack.
(3) some alloy elements, has the welding hot cracking tendency, especially in the steel containing vanadium, boron.
In order to avoid and eliminate the above defects, alloy steel requires preheating before welding, heat treatment after welding.
Preheating before welding, the main purpose is to improve the material weldability. In the process of heating and maintain a certain temperature can reduce the temperature difference between the welding joint area lessened the hardening tendency of heat affected zone. In the welding process for hydrogen escape, reduce the hydrogen content in the weld, prevent cold cracks, improve the plasticity and toughness of welded joint.
After heat treatment method is generally high temperature tempering, and its main purpose is:
(1) to eliminate or reduce the internal stress produced in welding process, to prevent the welding seam and heat affected zone cracks.
(2) improve the mechanical properties of weld seam and heat affected zone, namely to improve the plasticity and toughness, improve the hard brittle tendency.
(3) improve the microstructure of weld seam and heat affected zone.

General carbon steel welding performance is good, can need not preheating when welding and heat treatment. But for the carbon content is high, the stiffness of weldment, due to the large residual stress after welding, also need to preheat and heat treatment, such as carbon steel tube wall thickness in 30 mm.

Source: Yaang Pipe Industry Co., Limited (www.yaang.com)

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