Efficient turning of difficult-to-machine materials with advanced tools

Aeroengine components use a large number of new ultra-high-strength high-temperature alloys, powder alloy steels, single crystal alloys, and lightweight high-strength composite materials, which makes the cutting process more difficult and puts higher requirements on processing technology. When encountering some difficult-to-machine materials, the cutting test should be carried out as far as possible, and the appropriate tool materials and coatings should be selected to better adapt to the workpiece material and cutting conditions.

Engineering Technology Room Engineer Xu Min

Tool selection for processing nickel-based superalloys

Nickel-based superalloys are used to manufacture high-temperature bearing components and hot-end components for aerospace engines operating at temperatures below 650 ° C. However, due to problems such as hard spots, poor thermal conductivity, and high work hardening, they often restrict On-site processing. There are few researches on the selection of machining parameters and tool selection and tool wear for processing various nickel-based superalloys for various coated tools, making on-site processing very difficult. The main processing material of our company is GH2132, the length of incoming parts is φ10×2 000mm, the hardness is 320HBW; the batch size is 500 pieces/month; the surface roughness value of the parts after processing is required to be Ra=1.6μm, and the product aspect ratio is 18, which is typical. Slim shaft parts.

The company uses the CNC vertical slitting automatic lathe CKN1120IV produced by Sichuan Pushinjiang Machine Tool Co., Ltd. In view of the processing characteristics of nickel-based superalloys and the special processing methods of processing equipment, the hard coating blades are selected through the cutting test results and analysis. MT09T304-PM5-WSM30 is used for processing nickel-based superalloys; for the blade of nickel-base superalloy GH2132, the main declination is generally selected from 40° to 50°, and the secondary declination is generally selected from 0.5° to 3°. It is -10 ° ~ -20 °, it is not easy to appear built-up edge, can guarantee the surface quality of the part; cutting speed is preferably 95 ~ 120m / min, the feed amount is preferably 0.1 ~ 0.15mm / r, can ensure the surface roughness value Ra = 1.6 μm or more.

Tool selection for processing powder metallurgical tool steel

Powder metallurgy tool steel (AHP10V) has the advantages of uniform structure, fine grain, high yield strength and good fatigue resistance, but it has many high contents (such as chromium, cobalt, molybdenum, niobium, nickel, iron, niobium, etc.). The alloy element of the melting point and the high content of g phase make the powder metallurgical tool steel have a great strengthening effect. In a certain temperature range, the hardness increases with the increase of temperature, due to the chemical composition and uniqueness of the material itself. The porous structure has a certain fluctuation in hardness value in a small area. Even if the measured macro hardness is 20~35 HRC, the hardness of the particles of the components will be as high as 60HRC. These hard particles will cause serious and sharp edge wear, so the powder metallurgy superalloy is a typical difficult material.

Through the test comparison, the material of the material S05F was selected. The carbide 4205F blade material is a new technology designed to solve the cutting of various wear-resistant alloys. The material has finer grain and a thin coating of 4μm CVD TiCN-Al2O3-TiN. This blade is especially suitable for the finishing of powder metallurgical tool steel. It has good wear resistance and is suitable for small depth of cut. 4205F D-type cutting amount: v=30~60m/min, ap=0.25mm, f=0.1mm/r. Adopt a gradual increase in speed. Test results: The surface quality is very bad. The surface of the tool has a chipping phenomenon. After inspection, it is found that the blade is not fixed during installation, causing the blade to vibrate during the cutting process. Improved results: After repositioning adjustment, the cutting amount is: v=35m/min, ap=0.25mm, f=0.1mm/r. The effect is relatively good. The cutting is smooth, the length of each chip is about 5~6cm, and the chips are easy to control. The machined surface runout value is approximately 0.01 mm. After processing, the surface end jump value is about 0.01mm, and the effect is better. As shown in the figure, the tool wear condition is the tool wear condition after processing 5 pieces of products. When 10 pieces of products are processed, the edge and boundary wear are extremely serious, and the flank face also produces groove wear. Due to the poor thermal conductivity of the material, the material has a tendency to bond, and the sticky knife is easy to produce built-up edge. There is a large amount of metal carbide in the alloy. The cutting process is equivalent to grinding the tool. In addition, there are hard spots in the domestic materials. This pair of knives is highly impactful and destructive and therefore causes the above-mentioned wear.

Cutting method and tool wear

The advancement of modern cutting technology is the result of the combination of the development of advanced tool structures and the innovation of cutting technology, mining the potential of cutting machining from a deeper level and promoting the progress of cutting technology. Reasonable selection of blade geometry, cutting amount elements, attention to the influence of cutting angle, attention to changes in cutting force and chip, timely adjustment of tool processing parameters to ensure smooth cutting. Continuous technological innovation, improve production efficiency, meet the processing precision of drawings and process specifications, and improve the competitiveness of enterprises.