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Reg. 80
MATERIALS OF CONSTRUCTION

STEEL CASTING

Procedure for Welding


In order to maintain a high standard of workmanship in the practice of arc-welding to steel castings, the following general principles should be followed, but the precise technique will of necessity vary according to the circumstances.

Surface condition.- The surfaces of the steel, it is intended to weld should be cleaned and freed from all foreign matter, otherwise poor penetration and unsound weld metal may result.

The preparation for the welding of cracks should be of the U or V types. When the latter is used, the included angle should be not less than 70°C. Where cracks extend through the section of the casting, the choice between single and double preparation, U or V will be governed by (i) the thickness of the casting; (ii) the location of the defect. In double preparation, U or V the root of the U or V should be sufficiently open to ensure complete penetration.

Electrodes.- The electrodes shall comply with Regulations 94 to 98 for Grade A castings. Electrodes for Grade B and C castings should be agreed between the manufacturer and the Inspecting Officer.

The electrode manufacturer’s recommendations for the use of the electrode should be strictly followed.

Pre-heating.- Variations in composition, mass design, and the extent of welding required make it impossible to lay down specific rules to establish conditions under which pre-heating should be applied.

When after consideration of each casting in the light of the above variables it is deemed necessary to pre-heat, such pre-heating should be carried out at a temperature of 150-300°C (302-572°F).

Stress-relieving treatment.- When the welding is carried out after the casting has received its normal heat treatment, a further heat treatment may be considered necessary. This treatment need be applied only in cases where welding has been such as to induce either internal stresses which would be detrimental to the casting, or locally hardened areas which would cause difficulty in machining. Where this further heat treatment is applied, the casting, where possible, should not be allowed to go cold after welding, but should be charged into a warm furnace and reheated to a suitable tempering temperature which in general should be not less than 550°C (1022°F).

When considering the advisability of applying this further treatment, its effect on the physical properties of the castings should be borne in mind. If the treatment, or the welding itself is such that the physical properties will be adversely affected, the full heat treatment required to produce satisfactory qualities should be substituted.

 
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