Due to its excellent properties, carbide rolls are widely used in the steel industry and their hardness is very high. For the machining of cemented carbide rolls, CBN/PCD Inserts can effectively replace the grinding process to improve production efficiency. The following are the selection rules and precautions for CBN/PCD tool cutting of hard alloy rolls.

A.Selection rule of cemented carbide roll processing tools

1. Hardness:

(1) Cemented carbide rolls with hardness less than HRA90, MCBN grade or BNK30 grade CBN inserts can be used for large-volume turning. The grade CBN inserts is a block material which is sintered by CBN fine powder. There is no alloy substrate. Non-metallic as a binder, excellent in high-temperature red hardness, and large-volume turning of hard alloy rolls, the tool does not break or burn.  (2) When the hardness is greater than HRA90 carbide roll, it has exceeded the processing range of CBN inserts. Generally, CDW025 grade PCD inserts or resin bond diamond grinding wheel is used for grinding.  Generally, the higher the hardness, the more brittle the material is. When the cemented carbide is cut, the workpiece is scrapped at the edge of the cut. The workpiece is scrapped for high hardness. It can be chamfered in advance or accurately. Reserve the finishing allowance to avoid it.

2. Machining allowance and machining method

(1) When the outer surface of cemented carbide roll or the groove above R3 is used, for machining allowance, it is generally roughed by MCBN grade or BNK30 grade cutter, and then grinding with grinding wheel (resin bond diamond grinding wheel grinding) For external or circular, roll-type slotting and other forming grinding, generally use electroplating or metal bond diamond grinding wheel); for small machining allowance, it can be directly ground with a grinding wheel, or PCD tool for profiling (such as Customized diamond tools can be selected for the forming process such as chamfering and grooving).

(2) CDW025 diamond engraving cutter (also known as flying knife, rotary milling cutter) is used for the machining of the crater of the cemented carbide roll.

The roll is divided into new system and grinding. The above method is not only suitable for the reference of the new roll of the cemented carbide roll factory, but also can be used as the grinding wheel of the steel mill.

B. Precautions when cutting carbide rolls

1. Selection of cutting parameters

MCBN grade or BNK30 grade CBN tool for machining carbide roll: cutting speed Vc≤35m/min; feed depth ap≤0.8mm; feed rate Fr=0.25-1mm/r (depending on tool shape and machining roughness) , try to take a big value), dry cut. If PCD tooling is used, the knife depth (ap) value is recommended to be smaller.
 When using CDW025 brand PCD tool for profile turning and slotting, the feed Fr value is recommended to be 0.1-0.2mm/r; or 0.05-0.1mm/r, and the cutting fluid can be added.

2. Tool edge processing

When machining a cemented carbide roll, the tool may be passivated. The so-called passivation process is to solve the defect of the micro-notch of the cutting edge of the tool after cutting, so that the front value is reduced or eliminated, and the smoothness is achieved. Sharp and durable. However, the passivation treatment should not be too large, because the contact surface of the cutting edge of the cutter becomes larger after the passivation, and the cutting resistance also increases. The hard alloy roll belongs to a hard and brittle material, which is liable to cause collapse and damage the workpiece.
 At the same time, the cutting edge of the tool should not be too sharp. Too sharp will reduce the service life of the tool. Therefore, before purchasing the tool, try to communicate with our engineers to choose a more reasonable tool edge parameter.

C CBN Inserts for Carbide roll processing case