In high-speed wire rolling processes, the abnormal fragmentation of tungsten carbide roll rings is the primary cause of unplanned shutdowns, with thermal fatigue cracks accounting for over 65% of the cases. Faced with the instantaneous high temperature of 500-600°C on the roll surface and the drastic temperature difference between it and the cooling water at 35°C or below, as well as challenges such as chloride ion corrosion of water quality and imbalance in assembly stress, how can we maximize the lifespan of the roll rings? Based on on-site measured data, this article systematically dissects the key technical standards for the long-term operation of tungsten carbide roll rings from four dimensions: cooling system control, water quality management, precise assembly and grinding procedures.
What problems have been encountered during use?
Firstly, the most important cooling issue when using tungsten carbide composite rolls is the high water temperature in summer, typically around 39℃. Technicians have continuously explored the impact of water temperature and flow rate on the temperature of the rolls and established a temperature field model. Secondly, the problem of high chloride ion concentration in the cooling water has been addressed. Staff have increased filters and other measures to reduce the chloride ion content, improving the quality of the cooling water. Thirdly, the issue of unskilled employees’ turning skills has been tackled. In response to this, managers have added a profile gauge, which not only improves the employees’ turning skills and enhances the machining accuracy of the tungsten carbide roll ring’s profile, but also allows for checking the actual wear of the roll ring. Fourthly, operators use a flaw detector to inspect the tungsten carbide roll ring before use, which helps them identify micro cracks and refine the grinding technology.
Thermal Fatigue and Fracture: The Leading Cause of Roll Ring Failure
The use of tungsten carbide roll rings faces several key issues, mainly concentrated on thermal fatigue cracks, cooling control, installation accuracy, water quality management, and operational norms.
Thermal fatigue cracks and fragmentation are the most common failure forms of tungsten carbide roll rings. During rolling, the roll surface temperature can reach 500–600℃, while the cooling water temperature is typically below 35℃. The drastic temperature difference causes alternating thermal stress on the roll surface, which, with repeated action, leads to micro cracks. When the crack depth exceeds 0.2–0.4mm, the strength of the roll ring significantly decreases, and radial cracking is highly likely to occur, especially in cases of steel stacking accidents, where local high temperatures can cause multiple roll rings to explode in a chain reaction, resulting in severe equipment damage.
The control of the cooling system is of utmost importance. Maintain cooling water at 0.5–0.7MPa and 250–300L/min, with nozzles angled at 15°–30°, to ensure direct impingement on the rolling groove and prevent steam film formation that undermines cooling. Excessively high cooling water temperature or insufficient flow rate will intensify the thermal stress, shortening the lifespan of the roll ring.
The quality of the cooling water directly affects the corrosion resistance of the roll ring. Water with a pH value lower than 7.2 will accelerate the corrosion of the cobalt bonding phase, causing tungsten carbide particles to fall off; when the suspended solids in the water exceed 15mg/L, the impurities will act like abrasive materials, accelerating the crack expansion. Therefore, it is necessary to regularly test the water quality, maintaining a pH between 7.2–7.9, and controlling the chloride ion content.
Installation Standards and Lifecycle Management
Installation and assembly accuracy are crucial for preventing early failures. The contact surfaces between the roll ring, the sleeve, and the roll shaft must be clean and free of rust. They should be thoroughly cleaned with anhydrous alcohol before assembly. The hydraulic pressure should be precisely controlled at 40–45MPa. Excessive pressure will cause the roll ring to be under high tensile stress, while insufficient pressure will cause the sleeve to slip. Both can potentially induce cracks. When the temperature difference in winter exceeds 15℃, the roll ring should be preheated to avoid abnormal interference fit.
Rolling quantity management must be strictly implemented. The single-slot rolling quantity for 6-inch roll rings must not exceed 3000 tons. For 8-inch roll rings, the limit is 5000 tons. Once the tonnage exceeds these limits, the maintenance team must regrind the roll rings. They must use a feed depth of at least 0.01mm. This removes all micro cracks. The team should also set up a record system for each roll ring. This system tracks rolling data per slot. It also records grinding cycles and flaw detector readings. These practices support full lifecycle oversight.
Process Factors and Material Composition Affecting Roll Ring Performance
Poor guide alignment, raw material defects, and improper roll gap settings can cause impact or stacking. These issues add stress to the roll ring. The production team must regularly check guide alignment. They must strictly control incoming material dimensions and profile accuracy. They must also block foreign objects from the equipment. Tungsten carbide roller rings contain carbide particles bonded with cobalt. Manufacturers often add nickel or other elements to improve thermal stability and corrosion resistance. Different binder contents and WC grain sizes produce different roll ring grades.
Where are the advantages of tungsten carbide composite rollers?
Using tungsten carbide composite rollers instead of ball-milled cast iron rollers can not only increase the rolling tonnage, but also reduce the number of rolling grooves, roller changes, and downtime, effectively improving the production utilization rate and output of the rolling mill.
Production teams using tungsten carbide composite rollers can significantly boost product dimensional accuracy. With precise negative deviation rolling, they are able to lower rejection rates and raise the yield rate substantially.
Using tungsten carbide composite rollers can significantly improve the surface quality of the rolled materials, resulting in a high surface finish of the rolled steel with good appearance, effectively enhancing the market competitiveness of the products.
What are the applications of tungsten carbide composite rollers on finished rod products?
Since this year, Fushun New Steel and Ningxia Jianlong have adopted tungsten carbide composite roller technology.
Fushun New Steel now produces Φ12mm and Φ14mm rebar with these rollers.
The yield rate rose by 0.15 percentage points for Φ12mm and 0.14 percentage points for Φ14mm.
Daily operating time increased by 25 minutes.
Since July, Liaoning Jiyue has trialed the rollers for Φ16mm rebar.
The yield rate increased by 0.18 percentage points.
Q: Why do carbide rolls crack?
A: Primarily due to thermal fatigue. Surface temps hit 500-600°C while cooling water is <35°C, creating alternating stress.
Q: How to prevent roll ring cracking?
A: Strictly control water flow and pressure, use flaw detectors to inspect micro-cracks, and ensure feed amount during grinding is ≥0.01mm.
Q: What are the advantages of composite rollers?
A: Higher rolling tonnage, precise negative tolerance control, and improved surface finish of rolled steel.
If you have any Tungsten carbide rings,please feel free to contact us
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