Affordable

Affordable Machining Hardness Variety For Iron And Steel Castings
As for machining process, the hardness is an crucial issue. Too higher hardness will harm the cutters, and even trigger the failure of machining. Even so, as for the cast iron and cast steel, what is the affordable hardness range?

According to my knowledge in the iron foundry in China, the following hardness range is suitable.

1. The reasonable hardness range to cast iron

Typically, the hardness of cast iron is indicated by BH (Brinell Hardness) or HB (Hardness of Brinell). The hardness significantly less than HB 220 will be appropriate for regular machining procedure. In other words, they are suitable for typical steel alloy cutters. Most of iron foundries could machine the iron castings in this hardness range.

We suggest you to manage the hardness under HB 210. Simply because HB 220 is still a small challenging for the drilling and tapping.

Nevertheless, by the special steel alloy cutters or ceramic cutters, the cast iron with hardness below HB 300 can be machined.

2. The reasonable hardness range to cast steel

Since the cast steel is a lot more brittle than cast iron, so it can be machined much more effortlessly.

The cast steel with hardness under HB 330 can be machined by the regular steel alloy cutters. If we transfer it into Rockwell Hardness, it is about RH 35. The cast steel with hardness under HB 500 (RH 50) can be machined by the specific steel alloy cutters.

In brief:
As for Cast Iron
Below BHN 220: Regular
BHN 220 to BHN 300: Specific

As for Cast Steel
Beneath BHN 330, HRC 35: Typical
BHN 330, HRC 35 to BHN 500, HRC 50: Unique

BHN signifies Brinell Hardness Number. HRC means Rockwell Hardness.

The metal casting designers and foundries need to think about the hardness range cautiously, and arrange the production and machining method accordingly.

As for the cast steel gears, we generally make the rough casting with regular hardness, then machine and hob it, then do the heat therapy to increase its surface hardness, and finally grind it to remove the surface oxide surface.

Higher hardness will lead to the much more severe brittleness, so the affordable hardness range and heat therapy method is extremely critical for the outstanding components.

This post was from Dandong Foundry. For the entire write-up, please check Dandong Foundry Weblog.

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