SU1650765A1 - Method of treatment of steel products - Google Patents

Description

The invention relates to the chemical-heat treatment of steel products, in particular to cementation

2

the surfaces have become a solid carburizer, and can be used in mechanical engineering. The goal is to increase wear resistance under dry friction conditions. The method consists in heating the surface of the part in contact with graphite by passing a current of industrial frequency, carburizing to carbon concentration, providing the liquid phase, and cooling at a speed of at least 5000 ^ / s, followed by diffusion annealing at 800 - 1000 ° C for 5 - 10 hours. As a result of the use of the proposed method, we obtain more of nasal-resistant coatings with a lower coefficient of friction. Table 2.

The invention relates to chemical heat treatment, in particular to the cementation of the surface of the steel and its subsequent heat treatment in order to increase the wear resistance of products operating under conditions of dry friction.

The purpose of the invention is to increase the wear resistance under conditions of dry friction.

The method is as follows.

The surface of the part in contact with graphite, by passing a current of industrial frequency, is heated, carburized to carbon concentration, providing the liquid phase, and cooled at a speed of at least 500 ° C / s to form a layer of white iron. Then

subjected to diffusion limb at 800 - 1000 ° C for 5 - 10 h.

An example: The rubbing surface of a roller made of steel 45, used to feed bars for machining in a centerless lathe, is' brought into contact with a graphite powder. Electric current of industrial frequency with voltage of 12 V and power of 300-400 A is supplied to the roller and graphite powder (through a graphite plate). When passing an electric current, the surface of the roller heats up to 1280 - 1320®С and graphite carbonizes the steel to cast iron, which melts and diffuses into the depth of the steel roller. After carburization, the product is cooled at a speed of at least 5000 ° C / s with a speed of 1650765 A1

1650765

I'm getting white cast iron. The lifetime of the liquid iron depends on the strength of the current supplied to the electrodes.

The cooling rate can be adjusted by the current on the electrodes, as can be seen from table 1.

The hardness of the carbonized layer of the NCM 68 - 70. Due to the high hardness of the surface layer of the rollers, the rods have scratches and their depth of grinding on centerless lathes increases.

After heating the roller to 800–1000 ° C, holding at this temperature for 5–10 h and slow cooling, graphite appears in the structure of white iron. The use of rollers with a graphitized surface of white cast iron ensures their lubrication and during dry friction there are no scratches and scratches on the rods in this case.

Tests for wear resistance are carried out on the same samples, under equal conditions (counterbody: alloy VK-8). Firmness is studied on rollers, the surface of which is covered with white iron. The outer diameter of the rollers 35 mm, inner 16 mm, thickness 11 mm. The pressure is chosen to be 30 kgf / cm ^ ·, the sliding speed is 0.35 m / s.

The data of the comparative tests are given in Table.

From the data given in Table 2, it can be seen that the increase in wear resistance is achieved by the fact that the carbon-black and rapidly cooled surface of the component acquires the structure of white cast iron, from which, as a result, dif-

10 fusional annealing stands out graphite, which plays the role of lubricant. Preservation of the high hardness, the received wearproof self-greased structure provides high performance

15 ness under dry friction conditions.

Claims (1)

Claim A method of treating steel products, including cementation, carried out by heating the product in contact with graphite powder by passing an electric current directly through a conductive medium that saturates the current, characterized in that, in order to increase wear resistance under dry friction conditions, heating is carried out to 1280 1320 C, cementation carry out to the concentration of carbon, providing a liquid phase, then cooled at a speed of at least 5000 ° C / s and annealed at 800 - 1000 ° C for 5 - 10 hours Strength current, BUT Table 1 The nature of the resulting cast iron structure Cooling rate, ° C / s . . -. ------ Hardness NES 200 Half-cast iron, most of the carbon (~ 0.8%) is in the form of cementite Pe ^ S, perlite and ledeburit 3000 45-50 300 White cast iron, all carbon in which is in the form of cementite Pe ^ C, has pearlite and ledeburite in the structure 5000 65-70 400 White iron in which 6000 68-70 all carbon is also in the form of cement- * titus. B structure contains perlite and ledeburit 1650765 6 table 2 Technological modes of the process Character forming structures £ - friction coefficient Wear resistance g / km Known method - 0,297 0.251 Heating temperature Perlite, le 0.261 0,230 va 1280 ° C, temperature deburit, tse- annealing bath mentat and g 800 ° С, time from fit Gigout 5 h Temperature is Also 0.246 0,221 heating and annealing, respectively 1280 and 800 ° С, time annealing 10 h Heating temperature Perlite, ice- 0,251 0,220 Your annealing is boring, cement- legally 1320 and tit and graphite 1000 ° С, time from Gigout 5 h · Temperature is The same 0,224 0.186 heating and annealing, respectively, 1320 and 1000 ° C, the annealing time of 10 h