How to make your mild steel tube more durable in applications?
Technically, welding defects are a type of discontinuity that compromises the usefulness of a weldment for mild steel tube, which could render it unable meet minimum applicable acceptance standards/specifications. Welding defects can be welding process-/procedure-related, or related to the chemical composition or metallurgy of the alloy(s) being welded. How to avoid welding defects is a big issue for most users in life today.
Based on welding safety first of all, it seems very necessary for users to pay more attention to the welding defects in the practical applications. It is not unusual to find that, although the wrought form of a metal or alloy is resistant to corrosion in a particular environment, the welded counterpart is not. Further welds can be made with the addition of filler metal or can be made autogenously (without filler metal).However, there are also many instances in which the weld exhibits corrosion resistance superior to that of the unwelded base metal.
Generally speaking, there are a few methods available to minimize corrosion in order to prevent possible welding defects of pipes in use. 1)For China steel tube manufacturer, careful selection of materials and welding consumables can reduce the macro- and micro-compositional differences across the weldment and thus reduce the galvanic effects; 2)Surface Preparation: a properly selected cleaning process can reduce defects that are often sites for corrosive attack in aggressive environments. Stainless steel brushes are generally preferred because they do not form corrosion products capable of holding moisture; 3)Welding Surface Finishing: the weld deposit should be inspected visually immediately after welding. For example, China hot dipped galvanized steel pipe has a galvanization process in a mill to produce a protective layer on the steel pipe body. For smooth weld deposits, wire brushing may be sufficient; 4) Surface Coating: when a variation in composition across the weld metal can cause localized attack, it may be desirable to use protective coatings. The coating needs to be covered both the welding and the parent metal and often requires special surface preparation.
However, hot dipped galvanized steel pipe exhibits special problems when welding, mostly due to the unevenness of the coating. Especially square steel pipes have edges and corners typically right where welding is being done frequently have very thick, heavy zinc deposits which may interfere with welding much more than where the zinc has been applied evenly. In addition, hot dipped products typically have rough finishes which do not top coat very well, and top coating, especially with powder topcoats, has to be done within 48 hours to avoid difficulty with white rust formations.
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