The internal chip deep hole drilling is divided into a single blade internal chip evacuation and a multi-blade internal chip swarf deep hole drill. At present, carbide chips are mainly used for drilling deep hole drilling tools in China. There are many types and grades of cemented carbides. In addition to ordinary cemented carbides (YG, YT, YW), many new types of cemented carbides have been developed, such as fine grained and ultrafine grained cemented carbides (YG6X, YD15). ), surface-coated cemented carbide (YB120), hard alloy with rare earth elements (YW1R), etc. The grades of blade materials commonly used in domestic deep-hole drilling chips are mainly YG8, YT15, YT798 and YW1. Requirements for insert materials for internal chip removal deep hole drilling Internal chip removal Deep hole drilling is performed under closed or semi-closed conditions, cutting heat is not easy to spread, chip removal is difficult, and the rigidity of the process system is poor. When chips are generated during drilling due to continuous chips or jamming, they often cause chipping or twisting of the drill pipe. When the cooling fluid enters the cutting area during drilling, it will cause poor cooling and lubrication. Tool temperature rises sharply and accelerates tool wear. As the depth of the drill hole increases, the tool overhang increases, and the rigidity of the process system during drilling decreases. All of these, put forward some special requirements for the reasonable selection of insert materials for internal chip removal deep hole drilling tools: High strength, hardness, wear resistance and red hardness internal chip removal Deep hole drilling drilling, cutting force, cutting temperature High, abrasive wear, diffusion wear and even oxidation wear of the drilling blade are serious. Especially when there are some hard compounds in the workpiece, the wear is more serious. Therefore, the hardness of the tool material is required to be higher than the hardness of the processed material, and can be at a high temperature. Keep high hardness, good wear resistance and durability. Strong impact resistance Internal chip removal Deep hole drilling Drilling tool is easy to chip and twist, so the blade material should have strong impact resistance. The reasonable selection of internal chipping deep-hole drilling insert materials is similar to conventional cutting processing. The selection of drill bit materials for different material drilling is also different. The general selection principles are as follows: Drilling of ordinary carbon steel and alloy structural steel for ordinary carbon steel and alloy structural steel drilling, easy to control the chips, is a relatively easy to cut material. The choice of blade material grades is generally: YT15 for the guide block, YT789 for the outer edge of the drill bit, YT789 or YG8 for the middle and center teeth.
Figure 1 wrong tooth deep hole drill
Drilling of high-strength steels and ultra-high-strength steels High-strength steels and ultra-high-strength steels are difficult to machine with deep-hole drilling. They have difficulties in chip breaking, high cutting force, high cutting temperature, rapid tool wear, and low production efficiency. In general, carbide inserts with good impact resistance and wear resistance should be selected. In general, YD15 can be used for the guide block, drill outer cutter teeth, middle cutter teeth and center cutter teeth. High-temperature nickel-based alloys High-temperature nickel-based alloys have large cutting distortions, large work hardening tendencies, large cutting forces, high cutting temperatures, and rapid tool wear. The quality and accuracy of the machined surface are not easily guaranteed. The key when selecting the bit insert material should consider the wear resistance and the durability of the cutter. In general, YD15 is used as the guide block. YD15, YG10H or 643 is used for the outer edge, middle and center of the bit. Stainless steel, stainless steel precipitation stainless steel grades are 0Cr17Ni4Cu4Nb, 2Cr13, 3Cr13, 4Cr13, 1Cr18Ni9Ti, etc., its large cutting distortion, cutting force, high cutting temperature, tool wear, work hardening to make the processing hole accuracy and roughness worse. When selecting the blade brand, the bending strength and wear resistance are mainly considered. Usually, YG8 is used as the guiding block, and YG8, YW1 or 813 can be used for the outer cutting edge tooth, middle cutting tooth and center cutting tooth of the drill bit. Titanium alloys (such as grades TC4, TC6, TC11) are characterized by a small deformation factor, high cutting temperature, a hard and brittle metamorphic layer on the machined surface, and a severe sticking knife. In addition, titanium alloys react chemically with YT cemented carbides at high temperatures, resulting in adhesive wear and chemical wear. Therefore, when deep hole drilling is performed on titanium alloys, YG type hard alloy is mainly used as a blade material. In general, YG8 or YD15 can be used for the guide block, the outer edge of the drill, the middle tooth, and the center tooth. Drilling test effect analysis High-temperature nickel-base alloy drilling test The single-blade internal chip removal deep-hole drill bit was used to drill N901 high-temperature nickel-base alloy. The material of the tooth was selected as YD15, YG10H or 643 hard alloy. Tests show that in the range of reasonable cutting amount, bright C-shaped crumbs and spiral crumbs can be obtained. The tool has high durability, stable aperture size and small variation. The machining accuracy is IT9-IT10 and the roughness is Ra. 3.2 ~ 6.3μm, straightness error within 0.02mm. The precipitation stainless steel drilling test uses a multi-blade, tooth-clearing, deep-drilling chip with a deep-hole drill. The structure is shown in Fig. 1. The YG8, YW1, or 813 are used for the material of the cutting teeth. The deep hole drilling test is performed on the 0Cr17Ni4Cu4Nb precipitated stainless steel. The results show that only The geometric angle and cutting amount of the tool can be selected reasonably, and the ideal drilling effect can be obtained. For example, when the feed rate is 0.08-0.12mm/r and the cutting speed is 45-60m/min, the bright C-shaped chips can be obtained. And spiral curling, high tool durability, aperture size stability, a small amount of change, machining accuracy of IT9 ~ IT10 level, roughness Ra = 3.2 ~ 6.3μm, straightness error within 0.02mm.
Fig. 2 Drilling deep hole drilling
Titanium alloy drilling test drilling TC4 titanium alloy, use YG type cemented carbide (YG8 or YD15), drill bit structure shown in Figure 2, the key is to optimize the geometric angle of the tool, in a reasonable geometric angle, you can determine a reasonable Cutting range, when the feed rate is 0.12~0.16mm/r, the cutting speed is 30~40m/min, the drilling effect is the best, the drill has better durability, the hole size consistency is good, and the workpiece processing quality is stable. Accuracy can reach IT9 ~ IT11 grade, processing surface roughness Ra = 3.2 ~ 6.3μm. Because the processing process is stable, the radial force of the drill bit does not change much, the guide is reliable, the spiral groove phenomenon that occurs most frequently in deep hole drilling is eliminated, the deflection of the hole axis is reduced, and the processing quality of the deep hole is ensured. Concluding Remarks Choosing the material for deep-drilling with internal chip removal is one of the main technical measures for ensuring the deep-hole drilling progresses smoothly and improving the tool's durability. It is an important factor influencing the machining accuracy and improving the productivity. The material of deep-hole drilling inserts mainly depends on the properties of the material being processed. Different materials to be processed should use the corresponding hard alloys. For deep-drilling of difficult-to-machine materials, select blade materials such as YG8, YD15 with good strength, impact resistance, and wear resistance.
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