UA112934C2 - METHOD OF PRODUCTION OF POWDER CORROSION STEEL - Google Patents

Abstract

The invention relates to powder metallurgy. A method of manufacturing powder high-speed steel includes pressing the billets and subsequent sintering at a temperature above solidus temperature, using a mixture of powders of two compositions as the starting material for sintering: low-carbon high-speed steel with a carbon content of not more than 0.1 wt. %, and high-carbon alloy with a concentration of alloying elements, similar to the standard high-speed steel with a carbon content corresponding to the eutectic concentration, in a ratio that provides the final carbon content of steel at the level of standard for the selected grade of steel, providing 25-35 vol. % of the liquid phase during sintering at the melting temperature of the high carbon component. EFFECT: invention enables to obtain high-performance powder metal cutting tool with uniform distribution of carbide inclusions.

Description

The invention belongs to powder metallurgy, and more specifically to the technology of production of sintered metalworking tools from high-speed steel.

There is a known method of producing products from high-speed steels, which includes loading the powder into the capsule, cold vacuuming of the capsule with the powder, sealing it, heating with exposure at a temperature of 1050-1150 "С and deformation (Authority of the USSR Mo 884859, IPC B 22

E 33/20, publ. 1981). However, the tool obtained using this method has an unbalanced final structure due to internal stresses after the deformation operation.

The closest method of the same purpose to the stated one is the method of producing products from high-speed steel powders, which includes pressing of blanks and subsequent sintering in a vacuum at a temperature above the solidus temperature, which ensures the formation of 4-9 vol. 95 of the liquid phase in the sintering process (Aust. of the USSR Mo 1537706, IPC C 22 C 33/02, O822 E Z/10, publ. 1990). The disadvantage of this method is the high cost of the tool due to significant energy costs.

The task of the invention is to increase the energy efficiency of the production technology of sintered metalworking tools from high-speed steel.

The technical result is obtaining a highly efficient powder metal cutting tool with a uniform distribution of carbide inclusions.

The specified technical result in the implementation of the invention is achieved by the fact that a mixture of two powders with a concentration of alloying elements is used as the starting material for sintering, which corresponds to the concentration in standard high-speed steels, but differs in carbon content. In the first component mixture, the concentration of carbon does not exceed 0.1 mass. 95, in the second - the carbon content corresponds to the eutectic concentration (3.5-4.2 mab. Vol).

The ratio of two types of powders is chosen in such a way as to ensure the final concentration of carbon in the sintered alloy at the level of the standard for the selected grade of steel.

The sintering of the mixture of powders at a temperature above the melting point of the eutectic (u«MeS-MzS) leads to the melting of the high-carbon component of the mixture, which ensures the formation of 25-35 vol. 95 liquid phase. In the process of aging during sintering due to diffusion processes, the concentration of carbon in the mixture is equalized, which makes it possible to obtain a ready-made sintered high-speed cutting alloy with a standard chemical composition.

The use of a mixture of powders ensures liquid-phase sintering of high-speed steels at relatively low temperatures for this class of steels due to a more easily melting component - a high-carbon alloy, and also eliminates the technological operation - annealing to equalize the composition of the sprayed powder due to the presence of at least 65 95 low-carbon components. The presence of a liquid phase during sintering increases the mutual diffusion of alloying elements, which significantly shortens the duration of the process and allows obtaining a non-porous workpiece. The above factors lead to a significant reduction in energy consumption during the production of powder high-speed steel according to the proposed technology. As a result of liquid-phase sintering, it is possible to obtain a dense structure with a uniform distribution of carbide inclusions, which does not require further annealing to relieve stress.

Example 1. To implement the claimed method, low-carbon steel O1RbM5 with a chemical composition (wt. 905): 0.09 C, 6.18 MU, 5.26 Mo, 4.33 Si, 1.90 M, is used as the initial mixture of powders. 0.17 5, 026 Mn, 023 Si, 0.013 5, 0.015 P, the rest of iron and a high-carbon alloy with a chemical composition (wt. 95): 3.82 C, 6.45 MU, 5.12 Mo, 4.16 Sg , 1.84 M, 0.19 51, 0.20 Mp, 0.10 Si, 0.021 5, 0.026 P, the rest is iron, in a ratio in which the average carbon concentration in the mixture is 1.10-1.12 wt. 95, which corresponds to 71 volumes. 95 of the low-carbon component and 29 vol. 95 high-carbon component. The defined mixture of powders is subjected to cold pressing in capsules made of standard high-speed steel under a pressure of 600 MPa to a density of 85...90 RPM.

Next, the sintering temperature for the selected high-speed steel composition is determined according to the state diagram, which should be 10-15"C higher than the melting temperature of the eutectic (uiMeSyaMaS). For the selected high-speed steel LOREM5-MP, the liquid phase sintering temperature is 1150 7C with a holding time of 1 hour. Next follows final heat treatment (quenching from a temperature of 1210 "C and tempering three times at a temperature of 550 "C for 1 hour).

Example 2. Similar to example 1, but low-carbon steel O1RBbBM5K»5 with a chemical composition (wt. 905): 0.07 C, 6.26 MU, 5.54 Mo, 5.11 Co, 4.11 is used as the initial mixture of powders St, 1.94M, 0.16 5, 0.22 Mp, 0.15 Si, 0.019 5, 0.029 P, the rest is iron, and a high-carbon alloy with a chemical composition (wt. 95): 3.74 C, 6.63 MU, 5.12 Mo, 4.96 So, 4.21 St, 2.09 M, 0.15 51, 0.24

Mn, 0.19 Cy, 0.015 5, 0.031 P, the rest is iron, in a ratio in which the average carbon concentration in the mixture is 1.05-1.07 wt. 95, which corresponds to 72 volumes. 95 low-carbon 60 component and 28 vol. 95 high-carbon component. For high-speed steel LOREM5K5o-MP, the temperature of liquid-phase sintering is 1120 C with a holding time of 1 hour, followed by tempering from a temperature of 1220 "C and three times tempering at a temperature of 550 "C for 1 hour.

The mechanical properties of powder high-speed steel produced by the proposed technology and the closest analogue are given in the table.

Table

Method of Maoka stepi Temperature and amount of liquid and Porosity, mechanical production of steel r duration of sintering phase, 90 to strength, MPa

The nearest 1ORBM5-MP (1234 С, one hour | 09010 2500 analog 1ORBM5K5-MPI1220С, 40 minutes | (6.1.0 и1 2800

Proposed (1ORBM5-MP I1140S, buttock | 029.10 2560 method 1ORBM5K5-MPIT120S, buttock | 028.10 2820

Production tests showed positive results, it is planned to introduce the developed technology into production.

Claims (1)

FORMULA OF THE INVENTION The method of production of powder high-speed steel, which includes pressing of blanks and subsequent sintering in a vacuum at a temperature above the solidus temperature, which is characterized by the fact that a mixture of powders of two compositions is used as the starting material for sintering: low-carbon high-speed steel with a carbon content of no more than 0.1 mass 9b, and a high-carbon alloy with a concentration of alloying elements similar to a standard high-speed steel with a carbon content that corresponds to the eutectic concentration, in a ratio that ensures the final carbon content in the steel is at the standard level for the selected steel grade, providing 25-35 vol. 95 of the liquid phase during sintering at the melting temperature of the high-carbon component.