Trial-manufacture and application of as-cast low chrome alloy casting balls (1)
Chen Mulin. Development & Application of As-cast Low Cr Alloy Ball.
Development and application of as-cast low chrome alloy balls have been introduced. Proper chemical compositions and cast technology parameters have been via experiments determined to produce cast balls without heat treatment capable of being put into application in large and medium industrial ball crushers. With wear-proof and anti-crack, it is effective economically and clearly to replace other balls.
Keywords: as-cast low chrome alloy casting balls, metal mold casting, insulated feeder
At present, in the fields of metallurgy, mine, building materials, chemical industry, and electric power, the total annual consumption of grinding balls used in ball mills is about 1 million tons, of which the annual consumption of ball in iron mines is over 300,000 tons, which is an important cost index in mine production. In the past, the Daye Iron and steel (Group) Company, Wuhan Iron and Steel, used ordinary forged steel grinding ball, the annual consumption of nearly 4000 tons of steel ball, worth more than 17 million yuan. In order to reduce the ball consumption, in the MID-90s, the low chromium alloy cast ball was developed gradually. At that time, most kinds of casting balls had to be heat treated before they could be put into use. In this way, the production cycle was long, and special equipment and facilities were needed. Whether the cast ball of low chromium alloy can be used directly without heat treatment, especially whether it can be used normally in large and medium ball mills, is a subject that needs to be studied and practiced. For this reason, the mine has carried out a series of tests and trials, after more than two years of exploration, a better solution to this problem. After long-term grinding of iron ore, copper ore, and phosphate ore, the results show that the cast ball has excellent performance and obvious economic benefit.
1.Determination of trial – production scheme of cast ball
1.1Working condition of the casting balls
- Ore characteristics: Daye Iron Mine of Wisco is an extensive contact, metasomatic sicarn copper-bearing magnetite deposit. The ore type can be divided into primary ore and mixed ore. Its hardness F = 12 ~ 18, a small amount can reach F = 22, and the ore’s hardness is high.
- Grinding Technology: TWO-STAGE CLOSED-CIRCUIT GRINDING PROCESS, one stage grinding, the ball diameter of the machine is 125mm, the ball diameter of the second stage grinding machine is 60mm, the two-stage grinding machines are of the wet grid type with the diameter of 3200mm × 3100mm, and the rotating speed is 18r/min.
1.2 The performance index of casting ball is put forward
Compared with forged steel ball, low chromium alloy cast ball has an excellent difference in hardness and toughness. The forged steel ball has good toughness, few broken balls, but low hardness, low wear resistance, and high ball consumption; the low chromium alloy cast ball has high hardness, good wear resistance, and low ball consumption, but poor toughness and is easy to be broken. In particular, when the chemical composition and casting process design is incorrect, the cast low chromium alloy cast, ball quickly in the use of a large number of broken, causing ball consumption rise. In combination with casting and ball working conditions, the following mechanical properties and Energy Index requirements are proposed for low chromium alloy casting balls:
l HARDNESS: 45 ~ 56HRC
l impact toughness αk ≥7j/cm2(20mm × 20mm no notch, specimen)
l Standard cast ball (< 100 mm)3. 5 M drop ball test impact fatigue, life ≥8000 TIMES