SU834162A1 - Method of making cutting tools - Google Patents

Description

(54) METHOD OF MANUFACTURING A CUTTING TOOL

The invention relates to metalworking and can be used in mechanical engineering, mainly in tool manufacturing. Known methods for the manufacture of end cutting tools such as taps, countersinks, reamers, cutters, including welding of the cutting part of the tool material with the shank of structural steel, annealing, subsequent hardening, tempering dispersion hardening and machining of the cutting tool 1.. Welded shchi at the junction of tool material and structural steel after cooling the blanks to room temperature, gains a hardness of HRC 62-64 units. The high hardness of the weld zone is caused by quenching the martensite of the surface layers of the tool cutting part from the tool material during cooling. The microstructure of hardened steel is unsatisfactory. For the final heat treatment, quenching of the tempering of dispersion hardening, since the repeated quenching of hardened steel not only does not provide the required strength of the joint, but also leads to cracking. In order to prevent cracking during the quenching process, the welded billets are subjected to annealing, the duration of which is 14-36 hours. As a result, a ferritic layer 200-250 microns thick is formed in the weld due to the diffusion of carbon of the structural steel into the tungsten-containing tool material. Welded joints after annealing, having a significant ferritic layer, have a reduced strength. This low crush strength is due to the low strength of ferrite and the fact that the ferritic layer is a stress concentrator, resulting in a brittle fracture of the hardened tool. A known method for producing a welded cutting tool, including welding, relaxation tempering, heat for tempering; Quenching, quenching by placing the weld in the zone of preliminary and final heating and tempering. This method allows to increase the strength and cutting properties.

tool by eliminating the annealing of the workpieces after welding and reduce the complexity of heat treatment 2.

The purpose of the invention is to reduce the duration of the process while maintaining the properties.

The goal is achieved by the fact that the B method of obtaining cutting tools, including welding, heating for quenching, cooling to a temperature of relative stability of austenite, isothermal aging, cooling and tempering, cooling is performed at a speed of 10-50 ° C / s and welding is performed after isothermal exposure.

Performing operations in such a sequence prevents the formation of a ferrite interlayer in the welded joint and provides high hardness (62-68 u HRC) of the cutting part after triple tempering of the precipitation hardening. This is due to the fact that during accelerated cooling of high-alloyed austenite at a rate of Vox. 10-50 ° C / s to a temperature higher than M, but lower. (Mn + 400) ° C, the selection of alloying elements W, Co / lo.V does not occur. In addition, the transformation of austenite to martensite at the stage of isothermal holding at MM - (Mts-L 400 ° C) does not begin. Martensitic transformation occurs in the process of cooling the blanks after welding.

Example. The M16 taps are machined in the following sequence: a piece of dimensional workpieces, mechanical machining of the profile cutting part (milling grooves, centering, turning machining of the intake cone) of steel R9K5 and shank of steel 40X (with an allowance of 0.5 mm per side), grinding ends

welding, austenization of the cutting part in a barium bath at 1230 ° C for 3 minutes, cooling at a rate of 30 ° C / s and isothermal exposure in a salt bath at 400 ° C, face cleaning, diffusion welding on the UDS-2 unit at a temperature of Cretaceous zone 1100 ° С, cooling in oil, triple tempering of the cutting part at 560 ° С with an exposure of 1 h, hardening and tempering of the shank, grinding the shank and sharpening the cutting part of the tool.

Metallographic studies revealed that the manufacture of the tool in such a sequence practically prevents the formation of a ferritic layer.

At the same time, the tool manufacturing time is shortened due to the absence of relaxation tempering or annealing.

Claims (2)

1. Barsov A. I. Technological tool production. M., “Mashinostroenie, 1975, p. 214-215, 235-237. 2. USSR author's certificate number 539085, cl. C 21 D 9/22, 1975.