Precautions for Using Cemented Carbide Roller Rings

Cemented carbide roller rings are a kind of high-hardness and wear-resistant tool material, composed of tungsten carbide and binder metal. To fully take their advantages on the high wear resistance, long service life, and efficiency in the high-speed wire rod rolling, the manufacturers have to address the precautions below in purchasing and using cemented carbide roller rings: Before choosing the grade of cemented carbide roller rings for each mill stand, get to know the properties of each grade very well to make sure you match the right grade for all stands.

1) Installing Cemented Carbide Roller Rings

The mounting and installation of cemented carbide roller rings must strictly design process precision requirements. The fit between the roller ring, mill shaft, and tapered sleeve shall be appropriate— not too tight, not too loose. If too loose, verify process specification compliance before installation. Clean thoroughly the assembly surfaces of the roller rings, tapered sleeves, and shafts. Do not assemble by striking hammering or hard objects on roller rings.

2) Cooling During Rolling and Water Quality Requirements

During operation, roller rings are attacked by thermal corrosion, thermal fatigue, and thermal stress. They may quickly develop network-like thermal fatigue cracks. Increasingly severe cases of spalling block and even roller fragmentation can result from it. Therefore, to reduce the effects of thermal corrosion, thermal fatigue, and thermal stress on the roller rings during rolling as well as prevent them from breaking rollers (crack propagation) this needs to be slowed down for better service life of the grooves. Thus proper cooling is required for cemented carbide roller rings to achieve maximum performance from them. The general cooling specifications are: cooling water temperature below 25°C; water pressure 5–6 MPa; flow rate 24-30 m³/h per stand. The water spray should be radial at an angle of about 15-30° relative to the direction in which the roller ring rotates: more than twice the width of the groove and it must strike exactly into the groove. This means scattered or mist-like water spray is not acceptable.

Water quality requirements:

YGH series: Neutral or weakly alkaline water with pH ≥7.2

YGR series: Slightly acidic water with pH ≥7.2 or ≤7.2

Solid particle content: <15 mg/L

Determine Suitable Rolling Volume

Since micro-cracks in the grooves are unavoidable, it is important that once cracks attain a depth between 0.2 to 0.4 mm during rolling, the roller should immediately be taken off for regrinding. Over-rolling will accelerate the propagation of cracks and increase the risk of breakage. Suggested rolling volumes:

Pre-finishing stands: ≥6000 tons

Finishing stands 1–2: ≥4000 tons

Finishing stands 3–4: ≥4000 tons

Finishing stands 5–6: ≥2500 tons

Finishing stands 7–8: ≥2500 tons

Finishing stands 9–10: ≥1500 tons

Sizing stands: ≥1200 tons

Regrind grooves whenever micro-cracks have extended to a depth of 0.2 mm. Make sure that the regrinding process completely removes all existing cracks because any residual cracks will quickly propagate during the next rolling process and lead to breakage.

Recommended regrinding depths:

Finishing stands 9–10: 0.4–0.6 mm

Finishing stands 1–8: 0.7–1.2 mm

Pre-finishing stands: 1.2–2.0 mm