Causes and solutions of slag holes and cracks in casting defects

Casting slag hole (casting organic solvent slag inclusion or hydroxide slag inclusion)

Casting slag holes are open or closed holes on the casting. All or part of the holes are blocked by slag. The appearance design is arc-shaped and small spot like. The solution slag inclusion is not easy to detect. After the slag is removed, the smooth holes are generally distributed under the pouring position, around the inner sprue or in the blind area of the casting. The metal oxide slag inclusion is mostly distributed on the surface of the casting around the inner sprue in a network structure, sometimes in the form of thick flakes or arc clouds with wrinkles, Or strip-shaped interlayer is produced, and flocs are stored in the interior of the casting. When it is broken, it is usually broken from the interlayer. Among them, metal oxide is one of the root causes of cracks in the casting.

Causes of casting slag holes

The key of slag hole is caused by aluminum alloy smelting processing technology and pouring processing technology (including the wrong design scheme of pouring system software). Abrasive tools themselves are not easy to cause slag hole, and metal abrasive tools are one of the reasonable ways to prevent slag hole.

Ways to avoid slag holes in castings

1. The pouring software shall be properly set or forged vegetable fiber filter screen shall be applied.

2. Skew pouring method shall be selected.

3. Select the solution and strictly control the quality.

Casting crack (casting hot crack, casting cold crack)

The appearance of the casting crack is a parallel line or arc curve. The surface of the hot crack fracture is obviously oxidized by air and is dark gray or gray black, without metal texture. The surface of the cold crack fracture is cleaned and has metal texture. Generally, the external crack of the casting can be seen immediately, while the internal crack can only be seen by other means. Cracks are often associated with casting defects, slag inclusion and other defects, mostly in the inner side of the oblique angle of the casting, the joint of the thin and thick cross-sectional surface, and the hot spot area where the pouring riser is connected with the casting.

Causes of casting cracks

Metal die forging is very easy to cause cracks. Due to the lack of tolerance of the metal die itself and faster water cooling, it is very easy to cause the stress concentration and expansion of the casting, too early or too late mold opening, too small or too large pouring angle, too thin architectural coating layer, etc. it is easy to cause cracks in the casting, and it is also very easy to cause cracks when there are cracks in the abrasive die itself.

Ways to avoid casting cracks

1. Pay attention to the structure and process performance of the casting, make the positions with uneven wall thickness of the casting connect evenly, and select the appropriate arc specification.

2. Adjust the thickness of architectural coating and try to make each part of the casting achieve the specified water cooling rate to prevent great stress concentration.

3. Pay attention to the operating temperature of metal abrasives, adjust the gradient of abrasives, and properly pull out the core and crack, and remove the castings for slow cooling.