Carbide material HRC45 HRC58-68 turning technology and tool selection

With the continued development of the manufacturing industry, machine tool makers around the world are looking for new technologies to reduce the cost of producing machined parts and finished products. As a result, new machining technologies that are currently of interest to various manufacturers will be turned into carbide lathes. In the near future, carbide turning technology is expected to become more mature and widely used.

Carbide Turning Technology

Carbide turning is defined as: A machining process for turning hard workpieces with HRC45 and above. In general, the hardness of the work material can reach the range of HRC 58-68, and the material of the cutting tool is basically CBN (cubic boron nitride).

Carbide turning technology offers new machining options that do not require ultra-precision grinding. Of course, some of the precision requirements of the workpiece are easily deformed, and the special requirements of the workpiece, the grinding process, is a more appropriate choice. Carbide lathes are not a perfect replacement for ultra-high precision grinding, but they can replace a significant portion of precision grinding, reducing the expensive production costs of the grinding manufacturing process. Currently, the surface roughness of cemented carbide cut products is generally Ra0.2 to Ra0.4, the roundness reaches 0.0005 mm, and the dimensional accuracy can be controlled within 0.003 mm. After turning, the carbide turning process was found to be 4-6 times more efficient than the typical grinding process.

Rotating the hard part of the HRC62 without using rotating fluid cooling produces a large amount of heat. In typical cemented carbide turning, the temperature in the inflection point region can reach 926 ° C. In fact, local hot heating helps complete the turning process. The high heat of the turning point of the tool pre-anneals and softens the turning layer of the workpiece, making it easier to rotate the workpiece. During this turning process, most of the heat is generated by chip peeling. The depth of the turn should be as small as possible during the final turn to obtain a beautiful surface finish quality. Usually within 0.25 mm.

Today’s carbide lathes are widely used in the manufacture of automotive parts. Shanghai Automotive Gear Factory has been very successful in applying this technology to mass production. They use lathes instead of grinding after carburizing and quenching gears to perform the final precision machining of the final product. You can meet the design tolerances and surface finish requirements of your parts. The surface roughness of the workpiece to be machined reaches Ra0.2 to Ra0.4, the roundness reaches 0.0005 mm, and the allowable band of 0.003 mm reaches 1.67.

The Stability Of Continuous Processing

An important sign for processing hard materials is ensuring the stability of continuous processing. This is related to the overall dynamic stiffness of the machine tool, the turning tools, and the heat treated state of the workpiece.

The main part of the bed is filled with polymer (artificial marble) and has a large damping factor (generally eight times that of a cast iron bed). At the same time, the combination of linear rolling guides has a significant impact on the turning process of carbide materials, significantly reducing the vibration caused by turning and prolonging the time to rapidly return to static stiffness. Test results show that machine tool improvements effectively reduce tool chipping due to machine tool vibration and extend tool life. The accuracy of the machined workpiece is greatly improved, the variation in the tolerance range is reduced, and the surface quality of the workpiece is improved.

Another important factor in machine tools is the performance and accuracy of the integration of various axes of movement. Includes machine tool accuracy, geometric accuracy, electronic control capabilities, error correction, and general adjustment and thermal deformation effects. This is because the final machining result of the workpiece is completely determined by the performance and accuracy of the machine.

It is usually used in rough machining of cars and has a rotation depth of over 0.25 mm. CBN knives are used for finishing automobiles and have a rotation depth of less than 0.25 mm.

It is also necessary to control the heat treatment state of the workpiece to achieve the desired effect of turning carbide materials. In general, the requirement for changes in quench hardness is less than 2 points between HRCs. If the workpiece is a carburized part, the consistency of carburized layer depth is also controlled. Generally, the depth should be controlled within 0.8-1.2 mm.

The Advantages Of Turning Hard Materials

Compared to the grinding process, turning carbide materials has the following advantages:

• 1. A single lathe can perform both “soft turning” and ultra-hard turning. One machine tool is equivalent to two machine tools, saving space in the factory and reducing capital investment to purchase machine tools.
• 2. The chip efficiency of carbide turning is 4 to 6 times that of grinding.
• 3. In carbide turning, workpieces with complicated shapes can be processed with the single point lathe function of the turning tool. The grinding machine can grind complex workpieces only with a molded grindstone.
• 4. One program setting allows you to complete multiple turning operations, save time in handling and re-installing workpieces, and reduce workpiece damage.
• 5. Carbide turning can easily reach the surface roughness of Ra0.2-Ra0.4.
• 6. Carbide lathes can be adapted to various specifications of workpieces, especially in the mold industry. Satisfies the processing of various batches and complex workpieces.
• 7. Carbide turning tips are easier to handle than grinding tips and meet environmental protection requirements.
• 8. Low tool inventory cost.

Carbide turning is a viable technology that achieves excellent economic efficiency and excellent work quality, especially for highly dynamic and rigid machines. Carbide turning is not much different from general turning. Most manufacturers have introduced this new technology and can apply it to actual production.
Looking to the future, continuous improvement of turning technology and machine tool performance will gradually perfect the new technology of carbide turning and make it more widely used.