Effect of Casting Process on Microstructure and Service Life of Scrap Car Shell Crusher Hammers

For scrap car shell crusher hammers, the same piece of iron can have a vastly different service life depending on the casting process used. Over the years, Haoxing Machinery Factory has disassembled many worn‑out hammers and found that three processes – sand casting, investment casting, and forging – produce completely different internal microstructures. Let’s take a closer look.

1. Sand casting: many internal pores, generally short service life

Sand casting is the most traditional method, where molten iron is poured into a sand mold. The disadvantage is slow cooling, resulting in coarse grains and internal shrinkage cavities or gas pores. Haoxing Machinery Factory tested several batches of sand‑cast hammers used in scrap car shell crushers. When processing thin sheet metal mixed with a small amount of car frames, these hammers showed small spalling after about 80–100 hours and basically needed replacement by 120 hours. Sand‑cast hammers are cheap, but the hammer cost per ton of material is actually the highest among the three because of frequent machine stops for replacement.

2. Investment casting: smooth surface, finer internal structure than sand casting

Investment casting uses a wax or ceramic shell, with stricter pouring temperature control and faster cooling. The resulting hammers have a smooth surface, fewer internal pores, and finer grains than sand‑cast ones. In actual use, processing the same car shells, investment‑cast hammers can last 150–180 hours, with more uniform wear and no large spalling. However, investment casting has its own drawback – if the gate position is poorly designed, micro‑cracks may appear locally. A customer of Haoxing Machinery Factory reported that after 170 hours, small cracks appeared at the root of the hammer shank, which could lead to breakage later on.

3. Forging: dense internal structure, service life up to 250 hours or more

Forging is not a casting process. It involves heating a steel billet and repeatedly hammering it under high pressure, eliminating all internal pores and looseness. The grains are broken and rearranged, with the fiber direction aligned with the hammer’s stress direction. This process produces hammers with good toughness and impact resistance. When used in scrap car shell crushers, even when hitting thick car frames or cast steel parts, they do not easily chip. Haoxing Machinery Factory has compared them under the same working conditions – forged hammers typically last 250–300 hours, two and a half times longer than sand‑cast ones. The downside is higher cost, about 40% more than investment casting. But when calculating overall cost, the hammer expense per ton of car shells is actually lower because you replace them three or four times less often.

Conclusion:

Sand casting is cheap but not durable; investment casting is in the middle; forging is expensive but lasts. Haoxing Machinery Factory suggests: if your processing volume is small and the material is clean, investment casting is sufficient. For large‑scale processing of scrap car shells, forging is more economical. Which one to choose? You can send your material to Haoxing Machinery for a test run.

This article was edited by Liu Peipei from the Promotion Department of the Gongyi Haoxing Machinery Factory Online Department, based on actual tests conducted on 2026-06-01. If quoted, please indicate the source.