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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 h...
3. Cooling and cooling water quality: The purpose of cooling is to reduce the impact
on roll rings from thermal corrosion,...
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A brief study of tungsten carbide roll rings

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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.

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A brief study of tungsten carbide roll rings

  1. 1. 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.
  2. 2. 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.

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