Abstract: In order to prevent the oxide sheet and cooling water from entering the rolling mill bearing, the sealing structure of Φ450mm horizontal rolling mill bearing of roughing mill of high line rolling mill was improved. The improved roll bearing seal structure adopts two kinds of seal combination, namely radial clearance labyrinth seal and skeleton oil seal, which improves the sealing effect, reduces the rolling mill accidents, reduces the cost and has remarkable economic benefits.

Key words: high speed wire mill; Roll bearing; Be sealed; Structural improvement

1 Overview

The high line production line of the first line material plant of Xinyu Iron and Steel Co, Ltd. is a semi-continuous high-speed wire production line built after the reconstruction of second-hand equipment imported from Spain in 1991. In 1993 and 1994, the finishing mill group adopted the 45° torsional high speed wire rod finishing mill group developed by Beijing Iron and Steel Design and Research Institute for technical transformation the finishing rolling speed of the finished product is 50m/s, and the annual production capacity is more than 600,000 t. The bearing labyrinth seal structure design of Φ450mm and Φ350mm horizontal rough rolling mills is not reasonable, rolls are cooled by water during hot rolling, a large amount of cooling water and oxide powder enter the rolling mill bearings from the labyrinth seal, the roll bearing lubrication system is seriously polluted, the oil quality deteriorates, the performance deteriorates and the wear intensifies, which seriously affects the service life of rolling mill bearings.

2 Improvement Plan

In order to solve the problem of water entering the oxide sheet and other dirt in the bearing device of Φ450mm rolling mill, the sealing structure of roll bearing is analyzed to find out the reason and seek the countermeasures. Poor seal is one of the main reasons for roll bearing damage, if the external dirt intruded into the bearing seat, the first pollution is near the outside grease, so that the bearing parts surface wear, with the increase of dirt will gradually expand the wear surface, along the circumference of the formation of cracks and gradually expand, and finally make the ring crack, in serious cases will scrap the roll and bearing seat and other related parts.

The roller bearing adopts four row cylindrical roller bearings (FC5678220) with thrust bearings (deep groove ball bearing 6052). The radial load and the axial load are respectively borne by two kinds of bearings to play their characteristics. The small axial interval is conducive to the improvement of rolling accuracy. The inner and outer rings of the four-row cylindrical roller bearings can be separated and interchangeable, which makes the roller installation and disassembly convenient. When the roll is assembled (FIG. 1), the waterproof sleeve (6) rotates simultaneously with the roll (1), while the inner gland (5) is fixed to the bearing seat (4). The labyrinth sealing device is a labyrinth between the waterproof sleeve and the inner gland. There must be a certain gap between the waterproof sleeve groove and the protruding part of the inner gland to avoid collision between the two. Bearing grease lubrication, rolling mill for natural cooling water, through the maze clearance, wash away the grease in the bearing, and the oxide sheet into the bearing, resulting in the bearing oil shortage, and finally appear stuck burning phenomenon. Bearing seal structure is not reasonable, so that the sealing performance can not meet the production requirements.

According to the special working conditions, two kinds of seal combinations are used for roll bearing, namely radial clearance labyrinth seal and skeleton oil seal. During the improvement (FIG. 2), the original labyrinth structure is retained, that is, the inlay between the inner gland (5) and the waterproof sleeve (7) is very small, the inlay gap is 1.5mm, and the outer tongue size of the waterproof sleeve is extended for more effective waterproof, and the J-type oil seal (6) is installed between the inner hole of the inner gland and the outer circle of the waterproof sleeve. J-type oil seal can completely seal the gap between the gland and the waterproof sleeve, preventing or reducing the water and oxide sheet into the bearing. J-type oil seal has the advantages of wear-resistant, cheap and easy to install.

3 Use effect and economic benefit

The improved roll bearing device was put into use in early 2003, after being used on the roughing mill (a total of 14) in June and July, the number of "burning rolls" was greatly reduced, and some rolls were disassembled to check the use of roll bearings after rolling tonnage was off the line, and the surface was very clean, basically no impurities such as water beads and oxide scale, and bearings could continue to be used. In 2002 and 2003, the output from August to December was 230,000 tons and 260,000 tons respectively. The "roll burning" situation is shown in Table 1.

With the improved sealing structure, the installation is simple and fast, the sealing effect is good, the phenomenon of "burning roll" is greatly reduced, the consumption of bearings and rolls is reduced, the time of processing and replacing rolls is reduced, and the rolling production rate is increased. Only reduce and save bearing consumption, the annual economic benefits of more than 1.2 million yuan, due to reduce the "burn roll", reduce the replacement of roll time, improve the effective operation rate of equipment, can increase production by more than 30,000 t per year.