Repair and Maintenance Welding

There are probably more welders employed Fabrication welding and considerably low volume of welders are capable in Repair and Maintenance welding. The main reason is for the same is repair and maintenance welding is difficult compared to fabrication welding. This is the reason that most welding utility services category has very few experienced welders and they charge very high bills for their service.

Repair welding and surfacing are both considered in the field of maintenance welding and are covered together since they are both done by the same welders. Often it is extremely difficult to separate what is considered repair welding from maintenance welding, and surfacing can be included in both situations. The same basic factors apply to both weld repair and surfacing.

Parts break and wear out continually. It may be impossible to obtain another part exactly like the one that broke or wore out. This is particularly true of older industrial machinery, construction machinery, agricultural machinery, machine tool parts, and even automobiles. Repaired parts may be more serviceable than the original part, since they can be reinforced and the weaknesses of the original part can be corrected. It is often more economical to weld repair since the delay in obtaining the replacement part could be excessive and the cost of the new part would normally exceed the cost of repairing the damaged part.

Weld repair is commonly used to improve, update, and rework parts so that they equal or exceed the usefulness of the original part. This is normally attained, with the possible exception of weld-repaired cast iron parts that are subjected to heating and cooling. Weld repairs on cast iron parts subjected to repetitive heating and cooling may or may not provide adequate service life. The problem is that cast iron parts subjected to high-temperature heating and cooling, such as machinery brakes, furnace sections, etc., fail originally from this type of service and due to metallurgical changes the weld may fail again without providing adequate service life. Except for emergency situations, it is not wise to repair cast iron parts of this type.

The metal that the part to be repaired is made of has a great influence on the service life of the repaired parts. Parts made of low-carbon and low-alloy steels can be repaired without adversely affecting the service life of the part. On the other hand, high-carbon steels may be weld repaired but must be properly heat treated if they are to provide adequate service life.

It is absolutely essential that we know the type, specification, or composition of the metal that we are planning to weld. As mentioned above, it may be unwise to weld repair certain metals. But we should not weld on any metal unless we know its composition.

 

The economics of weld repairing are usually very favorable and this applies to the smallest or the largest weld repair job. Some weld repair jobs may take only a few minutes and others may require weeks for proper preparation and welding. Even so, the money involved in a repair job may be less than the cost of a new part.

A part made of any metal that can be welded can be repair welded or surfaced. In fact, some of the metals that are not normally welded can be given special surfacing coatings by one process or another. All the arc welding processes are used for repair and maintenance work. In addition the brazing processes, the oxy-fuel gas welding processes, soldering, thermit welding, electro slag welding, electron beam welding, and laser beam welding are also used. The thermal spraying processes are all widely used for surfacing applications. In addition, the various thermal cutting processes are used for preparing parts for repair welding.

The selection of the appropriate preparation process and welding process depends on the same factors that are considered in selecting a welding or cutting process for the original manufacturing operation.