SU1735393A1 - Method of heat treatment of the lap - Google Patents

Abstract

The invention relates to heat treatment and can be used in the manufacture and restoration of lapping, finishing calibration and marking plates. Essence: a gray cast iron slab is subjected to abrasive mechanical processing, then the initial tempering is performed by heating to 250 ° C and immersing it in molten solder with aging at 150 ° C to ensure the crystallization of the solder, then shock immersion into liquid nitrogen is performed, the second tempering is performed by heating to 150 ° C, then holding and heating to a temperature of 250 ° amp; deg; With providing melting solder. 1 hp f-ly.

Description

The invention relates to the field of abrasive processing of materials and is suitable for use in the manufacture, operation and restoration of ground-ups, finishing and calibration plates from metals and alloys, which are hardened by heat treatment.

A known method of heat treatment of an instrument in order to increase its wear resistance includes cold treatment by shock immersion in liquefied nitrogen at a temperature of -196 ° C and a single tempo of 200-250 ° C. A well-known method of removing residual stresses after abrasive-mechanical processing, processing cold at deep negative temperatures, in the material of the instrument and other products of gray iron, is to conduct a low tempering in the range of 150-250 ° C with an exposure time of up to three hours. The technique is widely applied coating based on tin and lead,

Providing effective corrosion protection.

There is a method of pouring tin parts with nystolead solder and cooling to the crystallization temperature to prevent plastic deformation of parts.

There is a method of heat treatment, including hardening, tempering, cold working and final tempering.

The construction of the priter is associated with the geometrical features of the workpiece, elements that reduce the weight of the product such as stiffeners, grooves, and minimal manufacturing costs. The accuracy requirements for the initial geometrical shape of the finished working surface are calculated in microns and their fractions.

Practical studies show that the existing method does not always allow to keep the raw materials in the process of combined heat treatment.

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the new geometric shape of the finished surface of the tool - priter. The unevenness of the redistribution of thermal gradients and their attendant stresses in places where the product material volume drops when the latter reaches the yield point of possible irreversible plastic deformations of the functional surface of the product. To restore the normal temperature of an instrument treated in liquefied nitrogen, depending on its size, it usually requires an exposure of an hour or more, during which periodically it is necessary to remove frost and moisture to prevent corrosion,

The purpose of the invention is to improve the quality of the working surface of the lap after the combined heat treatment.

The goal is achieved by the fact that in a known method, including abrasive-mechanical processing, tempering, cooling by shock immersion in liquid nitrogen, re-tempering after heating to tempering temperature, lapping is placed in the molten solder having melting and crystallization temperatures in the tempering temperature range of the part the cooling is carried out to a temperature that ensures the crystallization of solder with a holding time at this temperature; the heating under rest tempering is first carried out to a temperature below the temperature crystallization of solder with aging, and then up to tempering temperature with a vertical arrangement of the working surface of the pripir, providing uncoupling and spontaneous draining of the solder.

Experimental studies to assess the feasibility of a protective-fixing tin-nysto-lead solder to ensure the quality characteristics of the working surface of the lap in the process of combined heat treatment were performed by monitoring the processing results by the following factors: quantitative assessment of the deformation by changing the interferogram of the flat surface; by comparing the corrosion level to reduce the reflectance of the functional surface.

As the initial billet in the manufacture of ground with a flat working surface, calibration plates 160x160 mm in size from gray cast iron of СЧ 18-36 brand with the hardness of the working surface material НВ 168-172 according to GOST 10905-75 were used. The blanks were sanded and brought to the pre

prepared by cast iron with 400 × 400 mm lapping with silicon-carbide-based green finishing paste 63С GOST 3647-71 with the size of the main fraction of abrasive М20,

M7, MZ consistently in three stages. An increase in the reflection coefficient of the functional surface to a level of 60% was achieved by polishing with a paste based on finely dispersed alumina with a grain size of 1/0. Processing was stopped when the error in the shape of the working surfaces was 0.9 microns in the central zone with a diameter of 116 mm. The accuracy of the shape of the flat surface was estimated

5 glass below PI-120. The average value of the reflection coefficient was determined by the photoelectric gloss meter FB-2 relative to the reference aluminum sample with a reflection coefficient of 0.7.

The solder of the POS-61 was laid in metal baths and kept in an oven at 250 ° C until completely melted. The choice of POS-61 solder in this particular case is due to the fact that the onset temperatures and

The 5 ends of its crystallization, respectively 190 and 183 ° С, lie within the stabilizing tempering of 150-250 ° С of the lapping material. This allows cold treatment and tempering after it in a fixed state of the tool. Laps with the working surface coated with KO-075 GOST 11066-64 heat-resistant lacquer were heated to 250 ° C and immersed in liquid solder. Baths with details were transferred to

5, the furnace at a temperature of 150 ° C for 1 h, continued tempering to relieve stresses after machining and providing solder crystallization. After turning off the stove and cooling to 20 ° C

0 solder-lapped lapping were immersed in liquefied nitrogen until the reaction stopped. Processed by cold and restored to normal temperature, the products underwent a two-stage tempering at

5 150 I250 ° C with a vertical arrangement of the working surface of the lap, providing a spontaneous draining of the solder and unfixing the product.

After cooling to a normal temperature, cotton wool moistened with acetone was applied to the working surface of the instrument and covered with sheet glass on top to reduce evaporation of acetone. Lacquer residues

5 cleaned with cotton and acetone.

The study of patterns of interferograms in the controlled zone showed an increase in the arcuate bands and, accordingly, an error in the shape of 0.3 μm. The average reflection coefficient on the surface was not

below 50%, no traces of corrosion were observed.

On samples processed by a known method, the error was grouped at 2.1 μm. Changes in the widths of the bands, local bends, and rounding off with spots of extremes of the ordinate profile were observed. After being treated with cold, the surfaces of these samples were periodically removed with moisture from the process of restoring the normal temperature. In areas of the product where moisture was not removed, the reflection coefficient was no more than 30% due to the general darkening of the surface and corrosion. The shape of the surface of the priter was impossible to establish due to the non-adherence of the plate to it in places of corrosion.

Using the proposed method of heat treatment of the primer provides, in comparison with the existing ones, the possibility of fixing and corrosion protection of the working surface of the primer within the temperature and time ranges of tempering, which improves its quality after combined heat treatment.

Claims (2)

1. The method of heat treatment of the lap, including abrasive-mechanical processing, tempering, cooling shock immersion in liquid nitrogen, re-tempering, characterized in that, in order to improve the quality of the surface by maintaining the original geometry and preventing corrosion, after heating to the tempering temperature, the lap is placed in the molten solder, having melting and crystallization temperatures in the tempering temperature range of this part, is carried out podstuzhivaniya to a temperature that ensures the crystallization of solder with a dwell at this temperature, the heating under the second tempering is first conducted to a temperature below the crystallization temperature solder with a holding time, and then - to the tempering temperature. 2. A method according to claim 1, characterized in that the resale is performed with vertical location of the working surface priter.