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Stainless Steel Castings, Grey Iron Castings, Ductile Iron Castings

Welding Repair of Castings

Principle

1. Usually refers to castings that do not meet the acceptance technical conditions or order agreement, have casting defects but can be repaired.

2. The area and number of castings allowed for welding repair are specified. The defect type is usually specified in the casting drawing, technical conditions and relevant standards and agreements. Castings that pass the inspection after welding repair should not be listed as scrap.

Types of casting defects that are allowed to be welded: holes on the surface or through the casting (slag holes, sand holes, pores, etc.); casting cracks, cold shuts, undercasting; shrinkage holes and looseness on the surface or inside of the casting; mechanical damage on the surface of the casting.
Types of casting defects that are not allowed to be welded: honeycomb pores, pinholes; large-area scattered looseness; castings that are not allowed to be welded as specified in the drawings or technical conditions, or parts of the casting that are not allowed to be welded.

3. Small defects on the surface of the casting that do not reduce the structural strength and do not affect the appearance quality do not need to be repaired.

Method

Oxygen-acetylene gas welding method

Features: simple equipment, easy operation, strong adaptability, can be welded without preheating or with preheating; the weld space position is arbitrary; the welding quality is poor.
Application: used for low-carbon steel castings and copper castings working under static conditions; welding repairs on non-machined surfaces are not preheated, and welding repairs on machined surfaces are hot welding.

Arc welding

Features: simple equipment, flexible and convenient use, used for welding in any spatial position; cold welding, semi-hot welding and hot welding are possible; low productivity and high labor intensity; welding quality depends on the technical level of the welder.
Application: suitable for carbon steel castings, low alloy steel castings, stainless steel castings, aluminum alloy castings and copper alloy castings; used for castings that work under static, impact and vibration loads and require strong and dense welds.

Argon arc welding

Features: using argon as a shielding gas for welding, the welding quality is high; the weld space position is top welding; the arc heat is concentrated, the heat-affected zone is small, and the weld deformation is small.
Application: Suitable for aluminum alloy castings, titanium alloy castings, magnesium alloy castings, stainless steel castings, heat-resistant steel castings, high-temperature alloy castings and zirconium alloy castings; can work under various types of loads, and require strong and dense welds.

Welding Repair of Castings - RMC
Welding Repair of Castings in RMC

Key points of welding repair

When the surfacing welds on the surface of the casting overlap each other, the overlapping width of each weld should be less than 1/3 of the weld width.
In the process of welding repair, in order to reduce welding stress, the weld can be knocked, except for the first and last layers.
For castings that are not preheated or multi-layer welding, in order to reduce overheating at the weld repair, try to use small diameter welding rods and small currents, intermittent welding repairs (stop for a while after welding a section or a layer), so that the weld is slightly cool (not hot to the touch), knock off the slag and continue welding repair.
When defects found after processing need to be welded, the processed surface should be covered with asbestos board (asbestos cloth).
After preheating castings and high carbon steel and alloy steel castings, they must be slowly cooled. It can be covered with asbestos board or placed in the furnace for slow cooling.
If the welding area is large and the defect is in the important part of the casting, annealing should be done immediately after welding.
If large and small defects exist at the same time, they can be welded alternately or welded from small to large.
For welding of stainless steel castings such as ASTM CF20, overheating should be avoided, and cold water can be used to accelerate cooling.
Welding of defects in high-manganese steel castings should be carried out after water quenching. In order to avoid overheating the molten metal during welding, try to use small diameter electrodes and small current. Structural steel electrodes can be used for defects in general parts, and stainless steel or high-manganese steel electrodes should be used for welding of important parts.


Post time: Jan-17-2025