RU2533236C1 - Method to restore worn-out four-wing knife - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method implies deposit welding of the knife blade surface carried out sequentially from two sides in radial direction from the blade tips in fracture cones by the value equal to 1/3 of the knife blade length along the worn-out cutting edges by zigzag rollers. Electrode is imparted with transverse vibrations with the amplitude whose value is in direct proportion to the magnitude of wear.

EFFECT: invention allows improvement of restored four-wing knife quality due to deposit welding of additional metal compensating the wear onto nonworking surfaces of knives with maximal possible approaching to the fracture cones.

2 dwg

Description

The invention relates to repair production and can be used in the restoration of cross knives of industrial meat grinders with hot plastic deformation.

A known method of restoring cross knives described in the patent for the device No. 2103139. The method is carried out using a stamp for restoring cross knives, in which the restoration of worn cross knives is carried out by hot volumetric plastic deformation by moving under pressure the excess metal from the non-working rear surfaces of the knife blade to the worn cutting edges.

The disadvantage of this method is the low quality of restoration of the ends of the knife blades due to the presence of significant friction forces of the heated heated metal on the matrix walls, which impede the complete filling of the peripheral zones of the stamp engraving in the places of wear of the cutting edges of the knives, as well as the insufficient supply of compensating metal wear in the non-working peripheral part of the knife.

There is also a known method of restoring a cutting tool (patent No. 2113963), which consists in surfacing metal directly on the worn cutting edges of a cross knife, followed by heat treatment and flat grinding to a nominal size.

The disadvantage of this method is that the deposited working surface of the knife blade has a bimetallic structure different from the factory part with other physicomechanical properties that change the working conditions of the knife in friction with the grinder of the meat grinder, there are also tempering areas in the deposited layer and microcracks that contribute to local chipping .

The prototype is a method of restoring worn gears (copyright certificate No. 591303, IPC B23P 7/00. Publ. 02/05/1978, bull. No. 5), which consists in surfacing compensating metal wear on the non-working surface of the part with subsequent deformation and exposure to the main material of the part .

The disadvantage of the prototype is that ring surfacing does not provide uniform and sufficient for subsequent grinding allowance during shaping of the cutting edges along the entire length of the blade of the cross knife. The known method is designed to restore cylindrical parts with teeth and cannot be applied without significant modifications to restore flat parts of spatial forms with processes, which include a cross knife of an industrial meat grinder.

An object of the invention is to improve the quality of reconditioned cross knives by surfacing an additional compensating metal wear on non-working surfaces of the knives with the greatest possible approximation to areas of difficult deformation.

The technical problem is achieved by the method of restoring worn cross knives, which consists in surfacing on the surface of the knife blade material that compensates for its wear, and in subsequent deformation, while compensating wear material is deposited on the non-working surface of the knife blade, and during deformation they affect the main material of the cutting edge of the blade a knife. In the method according to the invention, surfacing is carried out sequentially from two sides in the radial direction from the side of the tips of the knife blades in areas of difficult deformation by an amount equal to 1/3 of their length along the worn cutting edges with zigzag rollers, giving the electrode transverse vibrations with an amplitude directly proportional to the amount of wear .

The difference between the proposed method and the prototype is that in order to improve the quality of the restored cross knives, surfacing is carried out sequentially from both sides in the radial direction from the ends of the knife blades in areas of difficult deformation by an amount equal to 1/3 of their length, along worn cutting edges with zigzag rollers giving the electrode transverse vibrations with an amplitude that is directly proportional to the amount of wear.

The combination of the claimed distinctive features allows us to solve the technical problem.

Figure 1 shows the deposition of the wear-compensating metal on the non-working surface of the cross knife, figure 2 is a section A-A in figure 1, illustrating the process of plastic deformation of the weld knife in the stamp.

The method is as follows.

A worn cross knife 1 is surfaced, for this purpose, on the non-working rear surface 2 of the blade 3 of the knife 1, a layer 4 of wear-compensating metal of length l equal to 1/3 of the length L of the blade 3 is sequentially applied on both sides of the blade 3. In this case, surfacing is carried out only from the side of the tips of 5 blades 3 along worn cutting planes 6 with zigzag rollers 7, imparting transverse vibrations with an oscillation mechanism to the electrode with an amplitude A directly proportional to the amount of wear I. Then the knife blank 1 with a layer 4 the metal that reduces wear is subjected to heating up to 1250 ° C and plastic deformation in the stamp, acting on the base material 4 of the cutting planes 6 ends 5 of the blades 3 of the knife 1 with a layer 4 of compensating for wear of metal 1. The arrows indicate the directions of movement of the heated metal in the direction of the worn cutting planes 6 of the blade 3. Compensation for wear and cutting planes 6 next to the not weld sections 8 of the blade 3 is achieved by some reduction in the thickness of the non-working rear surface 2 of the blade 3 by t without sacrificing the supply knife accuracy 1.

The length of the deposited rollers, equal to 1/3 of the length of the knife blades, is quite sufficient to compensate for the wear of the cutting planes of the knife in the area of the hard to deform the tips of the blades and at the same time create allowances for the subsequent double-sided flat grinding to the nominal size. In the absence of a deposited layer at the tips of the knives, the quality of the restoration sharply deteriorates due to the impossibility of obtaining a uniform and sufficient allowance in the peripheral parts of the cutting plane.

An example of a specific implementation. The method was carried out on laboratory surfacing, heating and press equipment in the conditions of the department "Processes and Food Production Equipment" of the Saratov State Agrarian University named after N.I. Vavilova.

Surfacing of the knife sections was carried out on the U-653 installation using the A-1406 machine using NP-65G surfacing wire. Surfacing modes: voltage 26-28 V, current strength 170 A, feed speed of the electrode wire 70 m / h, the amplitude of transverse vibrations of the mouthpiece of the oscillating mechanism is set from 3 to 5 mm depending on the amount of wear, which is 2-3 mm according to the results of defect, longitudinal feed of the surfacing head 2.5 mm / revolution of the lead screw.

The pre-deformation heating of the deposited knife blank to a temperature of 1250 ° C was carried out in an SN-3 chamber furnace, the subsequent hot volumetric stamping was carried out on a D-2434 hydraulic press. The stamping speed is 0.15 m / s.

The technological process of restoring worn knives by the proposed method includes cleaning, fault detection, surfacing, heating, stamping, heat treatment (normalization + high tempering, hardening + low tempering), grinding, control.

The pressure in the stamp of the blanks of knives deposited on a non-working surface with a wear-compensating metal was made according to the invention and the prototype, as well as without the use of welding (according to the analogue). The results of a comparative study of forgings and the restored knives of the MP-200K industrial meat grinders obtained from them showed that the parts restored by the proposed method increased to 100% the metal fillability of the peripheral sections of the stamp engraving, there appeared uniform allowances at the ends of the knife blades, sufficient for subsequent processing by cutting. In addition, additional thermomechanical hardening of the surfaces took place, foundry and fatigue defects were eliminated. Due to the rejection of continuous surfacing along the contour of worn surfaces, the consumption of surfacing materials decreased by 3 times compared to the prototype.

Claims (1)

The method of restoring a worn cross knife, including surfacing on the surface of the knife blade of a material that compensates for its wear, and subsequent deformation, while compensating for the wear of the material is deposited on the non-working surface of the knife blade, and when deformed, they affect the main material of the cutting edge of the knife blade, characterized in that surfacing on the surface of the knife blade is carried out sequentially from both sides in the radial direction from the side of the tips of the blade in areas of difficult deformation by an amount equal to 1/3 of the length of the blade, along worn cutting edges with zigzag rollers, while the electrode is given transverse vibrations with an amplitude, the magnitude of which is directly proportional to the amount of wear.

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