This article provides guidelines for the use of hard alloy roller rings in high-speed wire rod rolling. It covers aspects such as roller ring selection for the finishing mill, installation accuracy requirements, cooling water parameters and water quality standards, appropriate production output range, and methods for repairing rolling grooves, aiming to assist users in correctly purchasing and using hard alloy roller rings, thereby extending their service life and avoiding the risk of roller ring rupture.
Cemented carbide roll rings, composed of tungsten carbide and binding metal, is one kind of tool material with high hardness and good wear-resistance. In order to make full use of the above advantages of cemented carbide roll rings, the manufacturer of high-speed wire rod shall pay more attention to the following items during the course of purchasing and using it:
1. Make the correct choice for the cemented carbide used by the finishing mill
Before determining the grade of cemented carbide for every stand, we shall have a thorough understand about their properties so as to make the correct choice (Please refer to the preceding paragraph).
2. Installation of cemented carbide roll rings
The sleeve insertion and assembly of cemented carbide roll rings shall be carried out in accordance with the requirements of precision. There shall be appropriate space between the roll rings and axle or between the roll rings and sleeve. The fit is neither tight nor loose. You should check whether the roll rings conforms to the technological requirement and clean the mounting surface of roll rings,sleeve and axle before the installation. It is prohibited to beat the roll rings with hammer or other hard things while assembling.
3. Requirement for the cooling of roll rings and cooling water during the course of rolling
Because of the negative effect of heat corrosion, thermal fatigue and thermal stress, the net-shaped thermal fatigue crack usually appears while the collar working. With the increase of cracks, small parts may come off and even the roll rings is broken. We adopt the cooling method to reduce the bad effect, prevent the cracks from stretching and prolong the durability of rolling groove, which plays an positive role on the cemented carbide roll rings. The parameters of cooling water are as follows: temperature no more than 35, pressure of 0.4-0.6 Mpa, volume of 24-30 m³ per stand per hour, radial direction for spraying water, the angle of 15-30°between the spraying direction and rolling direction of roll rings. The water is twice as wide as the rolling groove and directly sprayed into the groove without scattering.
Cooling-Water quality requirement:
For YGH series medium or weak alkali water of PH≥7.2.
For YGR series or PH < 7.2 weak acid water.
The content of solid particles in the water<15 milligram/L.
4. Determine the reasonable yield
It is inevitable to find the microcrack on the rolling groove. The microcrack will gradually extend, stretch and deepen. The groove shall be repaired immediately while the depth of crack reaching 0.2-0.4mm. Otherwise, the crack will deepen quickly, which leads to a risk of broken roller. The range of normal yield is regulated as follows:
Stands of pre-finishing mill (6000-7000) Tons.
1-2 Stands of finishing mill rolling mill (2000-3000) Tons.
3-4 Stands of finishing mill rolling mill (2000-3000) Tons.
5-6 Stands of finishing mill rolling mill (1500-2500) Tons.
7-8 Stands of finishing mill rolling mill (1500-2500) Tons.
9-10 Stands of finishing mill rolling mill (1000-2000) Tons.
Stands for reducing diameter (1000-1500) Tons
5. Repair of groove
It is normal to find the microcrack on the rolling groove. The groove shall be repaired immediately while the depth of crack reaching 0.2 mm. It is necessary to prevent the roller from being broken. While repairing, we must ensure to remove the crack thoroughly. Otherwise, it will bring a potential risk to next rolling. It is difficult and inconvenient to check if the surface is polishing. To ensure the complete removal of microcrack, we can increase the grinding quantity. Under the normal condition, the repair is controlled in the range of:
- Roll rings for stands 9-10 of finishing mill rolling mill (0.4-0.6)mm
- Roll rings for stands 1- 8 of finishing mill rolling mill (0.7-1.2)m
- Roll rings for stands of pre-finishing rolling mill (1.2-2.0)mm