The cutting of superalloys includes traditional cutting methods such as turning, milling, drilling, tapping, broaching, and grinding, as well as physical and chemical methods, such as electrolytic cutting, electric sparks, and laser beam processing. method.
42.1 Turning of superalloys
42.1.1 Tool material
Carbide tools are generally used for turning superalloys. High speed steel is only used in interrupted cutting. Commonly used carbide grades for rough turning tools include YG8, YG10H, YG6X, YW3, etc., and carbide grades for fine turning tools include YW2, YG8, YD15, YS2, etc.
42.1.2 Tool geometry parameters
The selection principle of tool geometry angle [1] is as follows.
1. Rake angle 0
The size of the rake angle mainly depends on the type of alloy, the accuracy requirements of the workpiece and the type of blank. During rough turning, the rake angle should be larger, generally 0=10°~15°; during finish turning, in order to ensure machining accuracy and tool durability, the rake angle should be smaller, generally 0=0°~5 °. The machinability of cast superalloys is even worse, and 0=0° is usually taken. When turning superalloys with carbide turning tools with roughly similar performance, rake angles with basically the same size can be used. Experimental research shows that each superalloy has its own reasonable rake angle. Due to the good plasticity and high strength of superalloys, the chips are difficult to curl, and the chips are easy to wrap around the workpiece and the tool, so it is easy to hit the knife, affecting the product quality, and it is not safe. During the production, the broken (rolled) chip table can be made on the turning tool or the broken (rolled) chip can be broken (rolled) with an indexable blade. Short cylindrical spiral chips and swirl chips are good chip shapes.
2. Back angle 0
In order to reduce the friction between the tool flank and the machined surface, a larger relief angle should be selected. Appropriately increasing the relief angle can significantly reduce flank wear and improve tool durability. When turning deformed superalloys, the relief angle of the turning tool for rough turning can be 10°~14°; the relief angle of the turning tool for finishing turning can be 14°~18°;
3. Leading angle κr
The cutting angle κr has a great influence on the cutting of superalloys. Under the condition that the machine tool power and the rigidity of the process system allow, the smaller cutting angle should be adopted as much as possible. Usually the main declination angle κr=45°~70°. When the rigidity of the process system is insufficient, the main deflection angle should be increased appropriately.
4. Blade inclination s
During rough turning and intermittent cutting, the edge inclination angle should be negative, usually s=-10°. During finish turning, in order to control the flow of chips to the surface to be machined, it is desirable to take s=0°~3°.
In addition, the chamfering width br, the chamfering rake angle 01, the secondary deflection angle κ and the tool nose arc radius r also need to be carefully selected.
Table 42-1 Cutting speed and cutting condition parameter values for turning four superalloys
Workpiece material Tool material Cutting speed υ
(m/min) Conditions of use
GH2036 YG8 50 0=0=10°,κr = 45°,
r = 0.5mm, br = 0.2mm
f = 0.2mm/r, ap = 2mm
GH2136 YG8 32.2 0=0°, 0= 0=°, κr= 70°, κr =20°, r =0.2mm,
f =0.1mm/r, ap=0.5mm
YS2 >40
GH2135 YD15
(YGRM)
30 0= 0-15°, 0= 0=8°, S= 0°,
κr= 70°, κr = 20°, r = 0.1mm
ap = 0.5mm
K214 YG8 40 0= 0°, 0= 0=8°, S= 0°,
κr= 70°, κr = 20°, r= 0.1mm
ap = 0.5mm
YG6X 35
YW2 30
GH2135 YM051 75 0=14°, 0=6°, κr= 90°,
f = 0.07 ~ 0.11mm/r,
ap = 0.02 ~ 0.3mm
GH2132 YM051 56 0=14°, 0= 0=8°,
κr= 45°, f = 0.15mm/r,
ap = 1mm
Inconel 718YD15
(YGRM) 31-35 0= 22°, 0= 8°, κr= 90°,
S= 5°, f = 0.15mm/r
ap= 0.5mm, rn= 0.2mm
Inconel 718YM051 40.19 0=10°, 0= 8°, κr= 45°,
rn= 1mm, f = 0.35mm/r
ap = 0.2mm
YG6X 40.19
42.1.3 Selection of cutting amount and cutting fluid
The reasonable cutting amount range of superalloy is very narrow, but it has a great influence on cutting efficiency and tool life. The selection principles of cutting amount and cutting fluid are as follows [1].
1. Cutting speed υ
The cutting speed of cutting superalloys is mainly restricted by the durability of the tool. At different cutting speeds, the tool wear is different. The cutting temperature corresponding to the best cutting speed is called the best cutting temperature. When cutting superalloys with cemented carbide, the cutting temperature is generally 750~1000°C. The optimum cutting temperature range for turning superalloys is narrow. Below or above this temperature range, tool wear will increase.
Table 42-1 lists the reference values of cutting speed and cutting conditions for turning four superalloys.
2. Feed rate
As the feed increases, the cutting temperature rises, but the increase is not large, so the impact of the feed on the tool durability is smaller than that of the cutting speed. The feed rate should be as large as possible. If it is too small, the cutting edge will cut in the hardened layer, which will reduce the durability of the tool. Generally, the feed f is selected in the range of 0.1~0.5mm/r, and the larger value is used for rough turning, and the smaller value is used for fine turning.
3. Depth of cut
When cutting superalloys, the work hardening is serious. In order to avoid turning the turning tool in the chilled layer, the cutting depth aP should not be too small. For rough turning, the cutting depth aP=3~7mm; for finishing turning, the cutting depth aP=0.2~0.5mm.
4. Cutting fluid
When cutting superalloys, the effect of using cutting fluid is very significant. Compared with dry cutting, the cutting speed can be increased by 25%. However, cutting fluid is rarely used in cutting, because if there is intermittent cooling, it will cause cracks in the cemented carbide blade. In addition, the splash of cutting fluid will also affect the operation of workers.
For rough turning, 10-30% emulsion or 10% vulcanized emulsion can be used. When finishing the car, you can use oxidized kerosene or 75% kerosene + 25% oleic acid (or vegetable oil) or 60% kerosene + 20% turpentine + 20% oleic acid.
42.1.4 Turning of Inconel 718Alloy Turbine Disk [2]
Inconel 718alloy is a and phase-strengthened superalloy with excellent high-temperature mechanical properties. Its main use is to make aero-engine turbine disks. The structure and shape of the turbine disk is complex, and there are many difficult-to-machine surfaces, such as thin web profiles, narrow grooves, sealing teeth, ring-shaped cavity on the end face, large transfer arcs and other difficult-to-machine surfaces. Therefore, the machining labor of the turbine disk is very large, accounting for 51% of the total labor of the machining of the turbine disk. The turbine disc is made of direct-aging high-temperature alloy Inconel 718disc blank, and the tool is easy to wear. Therefore, the tool material is required to maintain sufficient hardness and good wear resistance and heat resistance at high temperatures. The tool material is YG8 and YD15 cemented carbide. Or use K313, K730 and K68 machine-added blades imported from the United States, and the effect is ideal [3]. The total machining allowance of the blank is large, generally 5~6mm (one side), and there are 10mm allowances in some places. During rough machining, a machine tool with high power and good rigidity should be selected, such as a vertical lathe, a faceplate lathe or a powerful CNC lathe. The diameter of the disk is large, the web wall is thin, the rigidity is poor, and it is easy to deform. During the processing, a heat treatment process for stress relief should be arranged. Special lathe fixtures should be designed for the finishing process; the fixtures should be designed with auxiliary support benchmarks to increase rigidity; the end faces should be pressed, and the pressing points should be at least six points. The structure and shape of the disk is complicated, and there are many inner and outer mating surfaces. A narrow ring-shaped cavity is formed between the mounting edge on the end face and the web profile, and there is a large transition arc in the cavity, and the opening of the processing part is poor. The profile and transition arc are processed by forming tools. The mutual position accuracy between the mating surface of the disc and the web profile is required to be high, and it is guaranteed by one-time clamping processing or the same datum positioning and alignment method.
1. Turbine turning process
2. Rough turning of turbine disc
Use a horizontal lathe for processing, clamp with a four-jaw chuck, turn the surface, and leave a margin of 4~5mm on one side. The tool material is YG8 cemented carbide, the tool geometric parameters: the rake angle and the rear angle are both 8°, the selected cutting amount is υ=8~10m/min, f=0.2~0.3mm/r, aP=2~3mm.
3. Fine turning of turbine disc
Thin wheel rims, web profiles, radial grooves, annular mounting edges, annular cavity surfaces, hubs and hub holes. The uniform allowance on one side is 1mm, and the surface roughness is Ra1.6m. Use ordinary lathe for processing and design special tools. The tool material is YW2 (R knife), YG8, YD15 cemented carbide, and the front and rear angles of the tool geometric angle are 8°~12°. Select the cutting amount υ=10~16m/min; f=0.1~0.2mm/r, aP=0.3~1.5mm.
4. Finish turning turbine disc datum surface
The outer circular surface of the rim of the turbine disc and the end faces on both sides are the common process benchmarks for the two sides of the finish turning disc. A high-precision lathe is used for processing, and it is processed to the size specified in the design drawing in one clamping. This process method can obtain good verticality (outer circular surface and end face) and parallelism (end faces on both sides). Select the special fixture designed by ordinary lathe to clamp the disc, press the end face, align the surface, and remove the allowance from the end faces on both sides according to the process pattern to ensure that the machining allowance on the finished surface is even. The tool material is YG8 and YD15; the cutting amount υ=8~10m/min; f=0.1~0.15mm/r, aP=0.3~0.7mm.
5. Turbine disc finishing machining
Choose an ordinary lathe, design a special lathe fixture to clamp the disc, and process each surface according to the sequence number in the figure. The tool material is YG8 and YD15. The selected cutting amount υ=9~12m/min; f=0.1~0.3mm/r, aP=0.3~0.7mm.
The above is the turning process of Inconel 718 direct aging turbine disk blank.
Tianjin Anton Metal Manufacture Co., Ltd. is a company specializing in the production of various nickel-based alloys, Hastelloy alloys and high-temperature alloy materials. The company was established in 2001 with a registered capital of 16.8 million, specializing in the production and sales of alloy materials. Anton Metal’s products are widely used in aerospace, chemical industry, electric power, automobile, nuclear energy and other fields, and can also provide customized alloy material solutions according to customer needs. If you need to know the price consultation of alloy materials or provide customized alloy material solutions, please feel free to contact the sales staff.
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Post time: Aug-26-2023
