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A brief study of tungsten carbide roll rings
Tungsten carbide is a well-known metal compound and is often referred to as hard metal
due to its very high hardness in relation to other metals. Tungsten carbide has a hardness
value of 1600 HV where as mild steel is in the region of 160 HV factors that is ten times
lower than tungsten carbide. Even though tungsten carbide is known as hard metal, it is
actually a composite material with hard particles of tungsten carbide embedded in a softer
matrix of metallic cobalt. The chemical formula of tungsten carbide is WC.
Tungsten carbide have a wide range of applications across many industrial sectors especially
in the metal machining, metal forming tools, oil industry, mining and cutting tips for saw
blades etc. Tungsten carbide roll rings are made up of tungsten carbide and cobalt well
known for its high hardness, and wear resistance. Tungsten carbide roll rings takes the
advantages of this metal compound of high wear resistance, long lifespan and high
efficiency in the form of high-speed rolling steel wire. Tungsten carbide roll rings are
used on the stretch reducing mills for seamless steel pipes with the durability of ten times
as common roll. The surface quality and the accuracy to size of the pipe are greatly
improved.
The buyers of tungsten carbide roll rings must pay due attention to following factors
when buying and using these roll rings and these factors are discussed in brief for the
benefit of buyers/users herein below:
1. Selection of grade: Before choosing the grades for roll rings, the buyer must have
a thorough knowledge about the properties of tungsten carbide. Choosing the correct
grade of roll rings used in the stands of rolling mills along with a perfect combination
of grades is required for the different stands of rolling mills. Some of the grades of
roll rings include YGH30, YG15 and types such as PR, CA, CO, RT, RO, and FO etc.
2. Installation of tungsten carbide rolls: Steel case mounting and assembly of roll
rings should be carried on strictly as per the precision required by the design
process. Excellent fitting is needed for roll rings, roll mandrels for stands and conical
sleeves that should not be too tight or slack. Before running the mill, it should be
observed that the roll ring meets the needles accurately. The rolls should not be
knocked with a hammer or other hard materials when running the mill.

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3. Cooling and cooling water quality: The purpose of cooling is to reduce the impact
on roll rings from thermal corrosion, fatigue and stress during milling. Cooling can
prevent the rolls from cracking and in slowing down the diffusion of cracks thereby
extending the life of grooves. This procedure also helps in getting the best
performance of roll rings. The water temperature should be below 25ºC and the
pressure of water should be 5-6 bars with a water volume of 24-30m3
/hr/stand.
4. Regrinding of grooves: Over a period, micro cracks would occur. However, when
these Micro cracks extend to 0.2 mm, the roll rings should be reground. Micro crack
must be reground thoroughly in regrinding. The following amount of regrinding is
recommended after normal rolling as mentioned below:
 Roll rings for stands for stands 9-10 finishing rolling mill 0.4 – 0.6mm.
 Roll rings for stands 1-8 of finishing rolling mill – 0.7-1.2mm.
 Roll rings for stands of pre finishing rolling mill- 1.2 – 2.0mm.