Air Cooled Bainite Steel Grinding Media

The air-cooled Bainite Steel Grinding Media described below have proved a wearing value of 70-80 g/t in mills where a good brand of High Chromium Casting Steel Media was showing a wearing value of 100 g/t.

The grinding efficiency of the air-cooled Bainite Steel Media is well above average because roundness is maintained by having virtually the same high hardness from the surface through to the centre of even the largest steel ball and rod.

The hardness on the Rockwell scale is 55-61 (HRC) and the impact strength is 10-14J/cm2, (High Chromium Casting Steel Balls from Germany, Canada, America and Belgium for comparison have an impact strength of 3-5J/cm2).

Ball-on-ball (3.5) impact tests of 120mm diameter balls have shown that the air-cooled Bainite Steel Grinding Balls can stand 28,432 dropping collisions without any spalling, macrocracks, breakages, or loss of roundness compared with only 10,000 drops with the High Chromium Cast Steel Balls.

Air-cooled Bainite/Martensite Steels are high harness high toughness steels. These two diametrically opposed properties are brought together through the addition of two relatively cheap but effective alloys and continuous air-cooling from the austenization stage, similar to the low carbon 0.5 Mo-B bainitic steels developed by Irvine and Pickering in the ninteen fifties.

A metallurgical research team of Tsinghua University under the leadership of Professor Hong-Shen Fang has developed this new fine grain Bainite/Martensite Duplex Structure Steel which offers a number of technical as well as economical advantages.

1. Air-cooling of steels provides for self-hardening of the steels eliminating costly quenching and elaborate tempering processes. The period of air-cooling can also be used for hot working of steels if required.
   
2. Possible defects from the quenching process like shape changes, cracking, oxidation and decarburisation are removed.
   
3. The transformation behaviour of the steel and the cooling conditions can be controlled within certain limits by adjustments to chemistry and heat treatment parameters. Thus the properties of the steel can be accurately predicted and controlled.
   
4. The steel properties can be tailored according to the wishes of the customer.
   
5. The process is less labour intensive, more energy efficient, and makes use of cheaper alloys. As a result, remarkable savings can be realised and passed on to the customer.

The steel and its manufacturing process have been patented internationally including the USA.

The steel has been extensively tested. Following the testing program the government of China formed, about four (4) years ago, the Beijing Bainite Steel Corporation.

The company's manufacturing activity is now on stream and expanding; it employs in excess of 25,000 people, a figure expected to double in the next 3-5 years.

The cost savings from the used of these grinding media are considerable in terms of prolonged service time, reduced power consumption, and quality of grinding output.

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