Study Of The Drillability Of NM360 High-strength Steels

Currently, tools for drilling high-strength steel are drills made of common high-speed steel and drills made of high alumina high-speed steel. However, it is found that low drilling efficiency and high worn of tools are big problems for Xiamen engineering machinery to drill NM360 high-strength steel with drills of high-speed drills.In this thesis, the process drilling of NM360 high-strength steel was studied. Firstly, based on analyses of mechanics of NM360 high-strength steel, three kinds of drills (YG8 hard carbide auger, coaled high-speed steel auger and common high-speed steel auger, the last one is presently used in the factory) were selected. Secondly, drilling experiments were conducted. Drilling power and axial force were measured and worn states of drills were micro observed. By comparing differences of tools abrasion resistance, drill force and power and analyzing factors of tool's worn were d and optimized drilling parameters for the factor were recommended.The main experiment results in this thesis are summarized as follows:1. Drilling experiments with Coated high-speed steel augers, YG8 hard carbide augers and common high-speed augers under the same drilling conditions show that the abrasion resistance of coated high-speed steel augers are highest and the abrasion resistance of common high-speed augers are lowest.2. Under the same drilling parameters, axial force of coated high-speed auger is the lowest among three kings of augers and axial force of common high-speed auger is largest. However, considered with machining cost, hard carbide augers are recommended.3. By micro observations of worn states of drills, worn on augers' flanks and chisel edges are found to be main factors for tools worn. By both actions of heaviest load on the outer of auger and extmsion on the chisel edge, high-speed auger tends to tip for its low hardness and hard carbide tends to fracture for its brittleness.4. In drilling with hard carbide augers, within the marching limitations, drilling parameters of n=1120mm/r, f=0.03mm/r are found to the optimizing parameters to this kinds of augers for its lowest axial force.5. During optimizing the chisel edge anger of hard carbide augers, it is found that the chisel edge anger of β(?) insignificantly affects axial force when it is lower than 77°. But when the chisel edge anger of β(?) exceeds 77°, with the increase of the chisel edge anger the axial force increases evidently.Generally, results in this thesis provide for a reference to factors to solve the technical problem.