Our Finland customer used the manganese steel shredder hammer to crush metal recycle material. However, the manganese hammer just can run around 150 hours. By analysis of the used hammer, the hardness of the used surface is only HB186-222. Only a few grains were found to slip on the use surface, and most of them were consistent with the matrix structure. So our engineer suggests 30CrNiMo alloy steel cast those shredder hammers.
30CrNiMo Chemical Composition
Nickel improves the hardenability and toughness of structural steel. When nickel and chromium are used together, the hardenability is very strong, far more than when the two elements are added alone. However, Cr Ni steel is sensitive to temper brittleness, which can be overcome by adding platinum. Adding a certain amount of rare earth in alloy cast steel can refine the structure of steel, purify the grain boundary, improve the inclusions, so as to improve the impact toughness and casting properties of the steel. Compared with other steels, Cr Ni Pt re steel is a kind of wear-resistant material with high hardenability, high strength, and high toughness. The specific chemical composition is shown in Table 1.
|Table 1. 30CrNiMoRe Alloy Steel Chemical Composition|
Smelting: the oxidation process is used in 5T EAF. Oxidation temperature ≥ 1550 decarburization amount ≥ 0.30%. The decarburization rate is not less than 0.01% / min. Before tapping, 1.0kg/t aluminum is inserted, and the alloy is added along with steel flow. Molding: resin sand for core sand, 8 pieces per box. The casting process performance of this steel is similar to that of medium carbon steel. In order to improve the casting density of the working part of the shredder hammer, a riser is placed on the head.
The heat treatment process is 900-920 ℃ water quenching, and tempering at 200 ℃.
After finish this product, we sent two sets to our customer. Based on customer feedback, this alloy steel shredder hammer’s span life can be 2-2.5 times than normal manganese steel hammer.