What is the effective feeding distance of the riser? How many types are there?

In the foundry industry, risers are used in factories, and there is also a commonly used term, which is the feeding distance. So, what is the feeding distance? What does it have to do with risers?

The sum of the riser zone and the end zone is called the riser feeding distance. Beyond this distance, axial shrinkage porosity occurs in the middle zone of the casting.

The feeding distance of plates and rods

Generally, a section with a width-to-thickness ratio of more than 5:1 is referred to as a plate-shaped part. A section with a width-to-thickness ratio of less than 5:1 is called a rod-shaped part. The following figure shows the effective feeding distances of risers for carbon steel (C=0.20-0.30%), with a thickness of no more than 175mm for plate-shaped parts and no more than 200mm for rod-shaped parts.

From the above, it can be seen that: (1) The effective feeding distance of the riser for plate-shaped parts is greater than that for rod-shaped parts. (2) The length of the end zone of the rod-shaped component is much greater than that of the riser zone. (3) The use of an external chill iron can effectively increase the effective feeding distance of the riser.

In addition, the effective feeding distance of the riser is also affected by the following factors:

(1) The solidification zone of thick castings widens, and the effective feeding distance of risers is relatively small.

(2) For cast steel with a wide crystallization temperature range, the effective feeding distance of the riser is relatively small. For cast steel with a narrower crystallization temperature range, the effective feeding distance of the riser is relatively large. For instance, the crystallization temperature range of carbon steel with a carbon content of 0.15% is narrower than that of carbon steel with a carbon content of 0.30%, and the effective feeding distance of the riser is 30% larger than the latter.

(3) The use of heating risers can increase the effective feeding distance of the risers.

2. The effective feeding distance of the riser of the wheel profile part

Wheel-shaped parts pay attention to the continuity of the riser. The continuity of the riser is the ratio of the sum of the root lengths of the riser (along the circumferential direction of the wheel) to the circumferential length of the wheel, which is called the continuity of the riser. The magnitude of the continuity depends on the thickness of the rim and the degree of requirement for its internal quality. For instance, the continuity of milled gears and cylinder blocks can be appropriately increased, while for unimportant and thick-walled wheel profile parts, it can be appropriately reduced.

(1) For general small parts (φ600mm) of wheel-shaped components without milling teeth, the continuity of the riser is taken as 25% to 35%.

(2) For medium-height and large and small gears and gear rings (the milling depth does not exceed 4/10 of the flange thickness), the continuation of the riser is 36 to 40%.

(3) For double-spoke and three-spoke gears with higher flanges, the continuity of the riser should be taken as 38% to 42%.

(4) For high-pressure cylinder parts that are under pressure and have flaw detection requirements, the riser continuity should be taken as full.