Comparative experiment of application effect of new component YFB modifier and light rare earth ferrosilicon alloy in chromium-based wear-resistant ball

Liu Yanping, Yang Qing, Zhu Fusheng, Zhong Weichang

(Longnan Longyttrium Heavy Rare Earth Technology Co., Ltd., Ganzhou, Jiangxi 341401) Abstract: This paper studied the influence of the new component YFB modifier on the metallographic structure, the number of inclusions and the mechanical properties of the grinding ball. The effects of ferrosilicon alloys in grinding balls are compared. After many comparative experiments, the modification effect of the new component YFB modifier is better than that of light rare earth ferrosilicon alloys. The cost is lower than that of rare earth ferrosilicon alloys. It can refine the matrix grains and carbides. It can degas and eliminate slag inclusions.
Keywords: new ingredient YFB modifier, grinding ball, refined carbide
1. Experimental background
Wear-resistant ball is a kind of pulverizing medium used in the ball mill, used to pulverize the material in the mill, a kind of white cast iron with chromium as the main alloying element, referred to as chromium alloy cast iron, casting mill with chromium alloy cast iron as the material The ball is called the chromium alloy cast iron grinding ball, and the other is the nodular cast iron grinding ball. The matrix structure obtained by heat treatment is mainly bainite. The nodular cast iron grinding ball is referred to as bainite. Ductile iron grinding ball. The test object in this paper is a chrome wear-resistant ball. Wear-resistant balls are widely used in metallurgical mines, cement building materials, thermal power generation, flue gas desulfurization, magnetic materials, chemicals, coal water slurry, pellets, slag, ultrafine powder, fly ash, calcium carbonate, quartz sand and other industries . According to statistics, the national grinding ball consumption in 2013 has exceeded 2 million tons, and the grinding balls consumed by metallurgical mines accounted for 70% of the total grinding ball consumption in various industries. Among them, the grinding ball consumption in the cement and building materials industry accounted for 45% of the main process consumption[1] . After long-term market research, our company found that most of the grinding ball manufacturers in the country will add light rare earth ferrosilicon alloy to purify the molten iron and modify it to improve the service life of the grinding balls. Studies have shown that rare earth has no significant effect on the number, morphology and austenite dendrite spacing of carbides in high chromium cast iron, but it can improve the composition and morphology of inclusions and reduce inclusions [2]. Although a single rare earth ferrosilicon alloy can play a part, there are still many problems, such as slag inclusions and pores that are not effectively controlled, and manufacturers that use automatic production lines often cause gate nodules to block the gate. . After many comparison experiments for our company, we believe that the new component YFB modifier developed by our company is better than light rare earth silicon, and the cost is lower than that of rare earth ferrosilicon alloy. It is convenient to use and will not increase gate nodules and block gates. The occurrence of the phenomenon, and can play the role of degassing and eliminating slag inclusions. After years of promotion, it has been used in batches in major grinding ball manufacturers across the country and has achieved very good economic benefits. Our company made full use of the unique advantages of yttrium-based heavy rare earths to develop YFB series yttrium-based heavy rare earth composite modifiers[3]. This experiment was further optimized on this basis, and further reduced production costs while ensuring the effect. , So that most manufacturers of wear parts can use them well and affordably.
2. Experimental method
The test ball composition is shown in Table 1
2.1 Test process
It is smelted in a 50kg intermediate frequency induction furnace. Pig iron and scrap steel are added to the furnace for melting. After they are melted, ferromanganese and ferrochrome are added. After melting, the temperature is raised to 1460℃ for slagging, and then slagging. The slagging is again heated to 1490℃ for aluminum Line deoxidation, slag off the furnace. Select the Φ80mm grinding ball as the test sample, adopt the iron mold sand coating process to produce, and cast at 1400-1420℃, use the graphite crucible as the casting ladle, cast 4 balls in one mold, and add 0.2% of modifier and rare earth silicon. . The modifier (rare-earth ferrosilicon) is added to the bottom of the bag, and the iron filings or slagging agent are appropriately covered, and then the molten iron is discharged. The molten iron cannot directly rush to the modifier (rare-earth ferrosilicon). After the deterioration treatment, the slag removal treatment is carried out immediately, and then the slag stopper is quickly poured into the iron mold, and can be cleaned out of the box after cooling. The medium chromium grinding balls are cleaned out for heat treatment, and the process is: oil quenching + tempering. Low chromium grinding balls are not heat treated. After the heat treatment, use an electric spark wire cutting machine to take 4 impact samples of 10×10×55mm in the center of each ball to prepare the metallographic structure and mechanical properties of the samples.

2.2 Sample preparation
2.2.1 Chemical composition of grinding ball
According to the more commonly used grinding balls on the market, the following two low and high chromium grinding ball components are selected for experiment, as shown in the following table: