Development and application of cubic boron helium

2022-08-15
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Development and application of cutting tool material cubic boron helium (CBN) (Part 1)

the 21st century is a high-tech era. What should we pay attention to when products must have high performance and high quality? How to choose a suitable and good impact testing machine? Let me start with my idea: only when there is a market can an enterprise have vitality. To this end, we should improve the level of manufacturing technology as soon as possible, and promoting the use of CBN tools to improve manufacturing technology is a powerful measure, which not only requires strong funding and support from the relevant competent departments, and gradually promote the technical support and use of CBN tools in an organized and planned way, but also requires users to be brave in accepting new materials and technologies, and change the old production concepts and management methods in the past, that is, the average consumption cost index of knives (grinders) is very low, It is only allowed to account for about 1/100 of the product cost, rather than to improve production efficiency and ensure product quality, which will limit the application of high-quality and efficient knives (grinders) and the production capacity of advanced equipment. Practice has proved that the effectiveness of CBN tool (grinder) can not only improve the processing quality of products, but also improve economic benefits

cubic boron helium nitride (CBN) is a new type of superhard tool cutting material synthesized artificially after artificial diamond. Its hardness is second only to diamond and is widely used in cutting and pin grinding

application of cubic boron helium (CBN) in machining

1 Finish Turning Hardened Steel with PCBN blade

Finish Turning Hardened Steel with PCBN tool, the workpiece hardness is higher than 45hrc, and the effect is the best. The cutting speed is generally 80 ~ 120m/min. The higher the workpiece hardness is, the lower the cutting speed should be. For example, for workpiece with turning hardness of 70hrc, the cutting speed should be 60 ~ 80m/min. The cutting depth of finish turning is 0.1 ~ 0.3mm, the structural feed into mhh-5 wood-based panel scratch tester is 0.05 ~ 0.025mm/r, the surface roughness of the workpiece after finish turning is ra0.3 ~ 0.6 m, and the dimensional accuracy can reach 0.013mm. If the standard CNC lathe with good rigidity can be used for processing, and the PCBN tool has good rigidity and sharp edge, the surface roughness of the workpiece after finishing can reach ra0.3 m, and the dimensional accuracy can reach 0.01mm, which can reach the level of processing with CNC grinder

if the machine tool has good rigidity and the selected cutting speed is low, the PCBN composite blade can be used to finish the intermittent surface| Mechnet | welcome to visit Chinese mechanical expert

the finishing machining allowance is generally about 0.3mm, so as to improve the dimensional accuracy of the workpiece before quenching and reduce thermal deformation as much as possible, so as to ensure uniform cutting allowance during finishing and prolong the service life of PCBN tools

generally, no cutting fluid is used for finishing turning, because at a high cutting speed, a large amount of cutting heat is taken away by chips, and rarely stays on the workpiece surface, affecting the quality and accuracy of the machined surface

the 80 rhombic blade with high strength and toughness should be selected as the fine turning blade, and the radius of the blade tip is between 0.8 ~ 1.2mm. In order to protect the blade edge, fine oilstone should be used for chamfering before use

fine turning and hardening workpiece is a new process. 3 before implementation, process tests need to be done. Bars with the same material, hardness and size as the workpiece can be used to carry out finish machining or rough machining tests on similar machine tools. The key is to test the selection of cutting tools and cutting parameters and whether the process system has enough rigidity. This process has been adopted in China at present. For example, FAW Group uses PCBN tools to process the carburized and quenched (58 ~ 63hrc) 20CrMnTi transmission gear fork groove, and the process parameters are c=150m/min, f=0.1mm/r, p=0.2 ~ 0.3mm, realizing the replacement of grinding with turning

2. Machining hard cast iron and gray cast iron

(1) machining hard cast iron

When Turning Hardened Steel with PCBN tool, the quenching hardness of the workpiece is required to be higher than 45 ~ 55HRC. When machining hard cast iron, as long as the hardness reaches the medium hardness level (45hrc), good machining effect will be achieved. Such as the exhaust valve seat on the cylinder head of the automobile engine industry, which is made of high chromium alloy cast iron containing copper and molybdenum, and its hardness is generally about 44hrc. The holes on the valve seat are countersinked (reamed) and turned. Most of them are processed on special automatic lines, together with gun reamed conduit holes. The cutting parameters used are: c=71.6m/min, f=26.5mm/min, p=1.0mm, BC broaching oil is used. Since the PCBN tool is used for processing, compared with the previous processing of various cemented carbide blades, the average durability of the tool is 1200 pieces, the machined surface roughness is Ra0.4 m, and the valve seat surface runout is 0.05mm. Since the engine plant of Dongfeng Motor Company used PCBN cutters in 1988, its effect has remained stable, which has better solved the problem of tool localization of imported equipment

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