RU2564654C1 - Method of producing of high density friction powder phosphorus-containing material based on iron - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: charge is prepared based on iron powder with carbon addition in amount of 1.0-1.2 wt % and phosphorous below 1 wt % in form of ferrophosphorus. Static cold pressing of the porous blanks, heating in shielding environment at temperature 1150-1250°C, hot forming at reduced compaction work 120-180 MJ/m³ are performed. Strain annealing is performed at 710-730°C for 2-4 h with assurance of fine pearlite structure, score 3-4, with solid or intermittent net of phosphoric eutectic, having maximum area of inclusions 2000-6000 mcm² and thickness of streaks 2.0-10.0 mcm.

EFFECT: increased friction coefficient and wear-resistance of the produced material.

1 tbl, 1 ex

Description

The invention relates to the field of powder metallurgy, in particular to materials based on iron powder, and can be used in the manufacture of medium and heavily loaded structural parts of frictional purpose, experiencing dynamic and abrasive loads.

A known method of producing a friction phosphorus-containing powder material based on iron, which consists in sequentially performing the following operations: preparing a powder mixture containing from 0.7 to 1.3 mass. % phosphorus, in the form of ferrophosphorus, cold pressing at a specific pressure of 35-40 kN / cm ² , sintering of billets in a protective medium at 1060 ± 10 ° C for 1 hour under a specific pressure of 150-20 MPa, which provides a phosphide network eutectics with vein thicknesses from 0.475 to 1.9 microns. The disadvantages of this method are the relatively low strength values due to the presence of residual porosity in the material [Effect of phosphorus on the frictional properties of a material based on alloyed iron / I.М. Fedorchenko, G.M. Derkacheva, I.I. Panaioti / Powder Metallurgy. - 1969. - No. 11. - S. 99-101].

The closest in technical essence to the proposed is a method for producing high-density phosphorus-containing powder material, which consists in sequentially performing the following operations: preparation of a mixture based on iron powder with the addition of phosphorus up to 1 mass. % in the form of ferrophosphorus and 0.1-0.8 mass. % carbon, static cold pressing of porous preforms, pre-deformation heating in a protective environment at temperatures and durations that ensure the formation of a liquid phase, hot stamping (GS) at reduced densities of 120-180 MJ / m ³ and homogenizing annealing at 710-730 ° C within 20-30 hours, followed by heat treatment [RF Patent 2494836, MAK B22F 3/17, C22C 1/04, publ. 10/10/2013, the prototype]. The disadvantages of this method are the relatively low values of the coefficient of friction and wear resistance due to the lack of a solid or torn phosphide eutectic network along the boundaries of particles and grains. The localization of phosphorus in the depths of the particles and grains of the matrix leads to a decrease in braking efficiency, and the structure of bainite-martensite, formed as a result of heat treatment, decomposes with increasing temperature in the friction zone during braking, which leads to a decrease in wear resistance.

The objective of the invention is to increase the frictional properties of the phosphorus-containing powder material based on iron, which makes it possible to use it in the manufacture of medium and heavily loaded structural parts of braking devices experiencing abrasive loads.

The technical result is to increase the frictional properties and wear resistance.

The specified technical result is achieved by the fact that in the method for producing a high-density friction powder phosphorus-containing material based on iron, including the preparation of a mixture based on iron powder with the addition of phosphorus up to 1 mass. % in the form of ferrophosphorus, static cold pressing of porous preforms, heating in a protective environment at a temperature of 1150-1250 ° C for a time determined from the calculation of 45-60 s / 1 mm of the smallest transverse size of the preform, hot stamping at values of reduced seal work 120- 180 MJ / m ³ , post-deformation annealing at 710-730 ° C, according to the invention, 1.0-1.2 wt. % carbon, post-deformation annealing is carried out for 2-4 hours, ensuring the formation of fine-grained perlite structure, score 3-4, the presence in the structure of the material of a solid or broken network of phosphide eutectic with the largest area of inclusions 2000-6000 μm ² and a vein thickness of 2.0- 10.0 μm. Heat treatment is not carried out.

Post-deformation annealing for 2-4 hours provides an insignificant diffusion redistribution of phosphorus, however, complete dissolution of the eutectic network along the grain boundaries does not occur. In this case, a fine-grained perlite structure is formed, GOST 8233-56 score 3-4, with a solid or broken phosphide eutectic network with the largest inclusion area of 2000-6000 μm ² and vein thickness 2.0-10.0 μm, localized at the former boundaries of iron particles rounded powder, which is optimal for obtaining enhanced frictional properties. The presence of a eutectic network with the indicated parameters against the background of the structure of fine-grained perlite causes an increase in the friction coefficient and wear resistance of the obtained material.

Example.

Additives of ground ferrophosphorus FF16 TU 14-5-72-76 and pencil graphite GK-1 GOST-4404-78 are introduced into a charge based on reduced iron powder ПЖВ 2.160.26. Then carry out static cold pressing (SHP) at a pressure of 500 MPa. As a result, blanks of prismatic samples with a size of 10 × 10 × 55 mm and porosity of 20-22% are obtained. Hot stamping of porous preforms is carried out on a copra with a mass of women 50 kg. Before hot stamping, the billets are heated in a batch chamber furnace with silicone heaters. Samples are placed in a container made of heat-resistant steel 10X23H18 (GOST 5632-72), which is placed in the working space of the furnace and purged with protective gas - dissociated ammonia. The exposure of the workpieces in the furnace at a temperature of 1200 ° C is 10 minutes.

After heating, the workpiece is placed in the mold for GSH and carry out compaction. The duration of the transfer of the workpiece from the furnace to the matrix is 2-3 s, while the temperature decreases by no more than 20 ° C. After hot stamping, the samples are annealed at 720 ° C for the time indicated in the table. The values of the indicators of the mechanical and frictional properties of the obtained samples are given in the table.

The analysis of the results of determining the mechanical and frictional properties presented in the table shows that obtaining high-density friction powder phosphorus-containing material based on iron by the proposed method provides an increase in frictional characteristics and wear resistance compared to the prototype method. The increase in the annealing time of more than the declared intervals will contribute to the decay of phosphide eutectic, reducing the thickness of the veins and the area of its inclusions, which are absent in the prototype. If the annealing time is less than the declared interval, then the thickness of the veins of the phosphide eutectic and the area of its inclusions will be relatively large. Thus, changing the optimal parameters of the technological process of obtaining the material does not provide the formation of the required structure, which leads to a decrease in the average and maximum values of the coefficient of friction, an increase in the wear of the friction material and the counterbody, as well as loss of braking efficiency when water enters.

The loss factors Δj _n and recoverability Δj _in braking efficiency are calculated by the formulas [GOST 4.79-87. The system of indicators of product quality. Friction products for brake mechanisms. Nomenclature of indicators]:

where f _n = f _cp is the coefficient of friction before water _{enters the} region of the friction pair;

f _k - coefficient of friction after water ingress;

f ₀ - coefficient of friction after drying of the friction pair.

Claims (1)

A method of obtaining a high-density frictional powder phosphorus-containing material based on iron, including the preparation of a mixture based on iron powder with the addition of phosphorus up to 1 wt.% In the form of ferrophosphorus, static cold pressing of porous preforms, heating in a protective environment at a temperature of 1150-1250 ° C over time , determined from the calculation of 45-60 s / 1 mm of the smallest transverse size of the workpiece, hot stamping with values of reduced seal work of 120-180 MJ / m ³ , post-deformation annealing at 710-730 ° С, characterized in that 1.0-1.2 wt.% of carbon is introduced into the charge, post-deformation annealing is carried out for 2-4 hours to ensure the formation of a fine-grained perlite structure, score 3-4, with a solid or torn phosphide eutectic network having the largest inclusion area of 2000 -6000 μm ² and a vein thickness of 2.0-10.0 μm.