CBN tool for the experience of turning in the rolling industry

**First, the selection of machine clamp tools commonly used in roll turning:** Heavy-duty rolls are typically processed using heavy-duty roll lathes, and square inserts such as 40x40 are frequently used. Common shank angles include 45-degree cutting tools and round insert tools. Smaller rolls may also use 25x25 or 32x32 holders. The main cutting edge angle is selected based on the "long diameter ratio" of the roll. For slender rolls, a 90° or 75° tool is usually preferred, while thicker rolls are often machined with 45° or round inserts. **Second, selecting CBN insert sizes according to cutting parameters and processing conditions:** When using BN-K1 grade cubic boron nitride (CBN) inserts for cast iron rolls, common size models include RNMN200800, RNUN200800, RNMN150700, RNUN160800, RNUN150716, and RNMN150716. For forged steel cold rolls, BN-S20 grade CBN inserts are typically used, with common blade types such as SNMN120712, SNMN120412, SNMN120408, and RNMN120400. The turning tool and CBN insert are shown in the figure below:

**Third, guidance on blade (insert) selection and cutting parameters for roll turning:** The selection principle includes: 1. Roll material, 2. Roll hardness, 3. Cutting allowance, and 4. Heat treatment method. Based on the material of the roll, the blade can be divided into three categories: 1. Rolls with lower hardness: Examples include ductile iron rolls and high-alloy cast iron rolls, often used in hot rolling, backup rolls, and intermediate rolls. These rolls have lower hardness compared to work rolls and can be machined with standard alloy tools. Common grades include YG6 or YG6X. 2. High-hardness cast iron rolls: Such as chilled cast iron rolls, high-nickel-chrome rolls, high-chrome iron rolls, boron-containing high-speed steel rolls, semi-steel rolls, and nickel-chrome-molybdenum centrifugal composite rolls. These rolls are hard and often have casting defects like porosity and sand inclusion. They require blades with high impact resistance, heat resistance, and wear resistance. In the past, ceramic inserts were used, but they tended to break easily. Now, BN-K1 grade CBN inserts are widely used due to their high impact toughness, making them ideal for rough machining. For example, a high-nickel-chrome cast iron roll with HSD82 hardness can be machined using BN-K1 grade HLCBN. The unilateral cutting depth can reach up to 12mm, and the feed rate is around 1.5mm/r.

3. High-hardness forged steel cold rolls: Examples include GCr15 bearing steel rolls, Cr3, Cr5, 86CrMoV7, and 9Cr2Mo rolls. These are forged and undergo heat treatment before being used as cold-rolling work rolls. BN-S20 grade CBN inserts are commonly used for these applications. BN-S20 is a high-performance CBN insert developed under a national key project. It uses fine CBN powder and non-metallic binders, offering better toughness than the BN-K1 grade. It is specifically designed for long chip formation during cold rolling of forged steel. Its wear resistance is about three times that of standard CBN inserts. Cutting parameters for BN-S20 grade CBN inserts when machining cold-rolled forged steel work rolls: (1) For a Swedish forged steel roll with HRC67 hardness, the cutting depth is 4–7mm, and the cutting speed is 90m/min. The blade life is 2.5 times that of a foreign brand CBN insert. (2) When machining 9Cr2Mo cold-rolling work rolls, BN-S20 achieves excellent results, with a blade life more than four times that of domestic CBN inserts. It prevents cracking during machining, ensuring safety and cost-effectiveness. **Fourth, roll material and common hardness ranges:** BN-K1 and BN-S20 grade CBN tools can process rolls with varying hardness levels. If the roll hardness is below HSD70, conventional carbide tools like YG6 or YG6X can be used. For rolls with hardness above HSD75 or even HSD110, BN-K1 and BN-S20 grades are recommended, depending on the material. Hualing Superhard Tool Development Department emphasizes that roll hardness alone is not the only factor in choosing the right tool. Instead, it's crucial to select the appropriate CBN grade based on the roll material for optimal performance.

Optoelectronic Chips

Optoelectronic Chips

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