SU1735428A1 - Tool steel - Google Patents

Abstract

Usage: the invention relates to metallurgy, in particular to tool steel of high hardenability, intended for parts operating under conditions of wear and dynamic loads. Steel additionally contains boron, aluminum, calcium in the following ratio of components, wt.%: Carbon 0.88-0.93; manganese 0.38-0.42; silicon 1.2-1.24; chromium 0.95-1.05; molybdenum 0.28-0.31; vanadium 0.18-0.22; boron 0.0028-0.0033; calcium 0.08-0.12; aluminum 0.04-0.06; iron else. 2 tabl,

Description

The invention relates to the metallurgical industry, in particular to tool steels, operating under conditions of wear, dynamic loads and requiring increased hardenability. Known steels chrome 9XC, containing, wt.%: Carbon 0,85-0,95; silicon 1.20-1.60; manganese 0.30-0.60; chromium 0.95-1.25; iron the rest, and steel, which contains, wt%: carbon 0.90-1.50; silicon 0.80-1.50; manganese 0.60; chromium 0.30-1.50; aluminum 0.05; iron else.

The disadvantages of steels are lower hardenability, impact strength, wear resistance, and insufficiently high performance properties.

Closest to the proposed technical essence and the achieved effect is steel containing, wt.%: Carbon 0.80-1.60

Silicon0.15-1.50

Manganese 0.40

Chrome 0.80-1.80

Molybdenum 1.50

Vanadium 0.50

IronErest

The disadvantage of steel is insufficient impact toughness, hardenability and low wear resistance.

The purpose of the invention is to increase the strength properties, hardenability, toughness and wear resistance of steel.

This goal is achieved by the fact that in steel containing carbon, silicon, manganese, chromium, molybdenum, vanadium, iron, boron, calcium and aluminum are additionally introduced in the following ratio, wt%: Carbon0.88-0.93

Silicon1.20-1.24

Manganese 0.38-0.42

Chrome0.95-1.05

Molybdenum 0.28-0.31

Vanadium 0.18-0.22

Bor0.0028-0.0033

Aluminum 0.04-0.06

Calcium0.08-0.12

IronErest

The specified carbon content provides hardness after quenching and subsequent tempering. Reducing the carbon content lowers the tempering temperature to obtain a hardness of 60-58 HRC3. Increasing carbon content over 1.00

cl

with

h

GJ SL 4 S 00

wt.% decreases plasticity (impact strength decreases).

Silicon in the specified amounts is a doping element and increases hardenability and wear resistance.

Manganese is not a doping element, but acts as a deoxidizer.

Chromium, within the limits specified, has a positive effect on wear resistance, but reduces toughness.

Molybdenum, within the specified limits, increases the hardenability of steel and its heat resistance at tempering temperatures of 400-600 ° C to 56-46 HPCE and expands the range of using steel as a heat-resistant material, which is important in the manufacture of cold-formed die tools . An increase in the molybdenum content of 0.30% by weight is impractical because of the increase in the cost of steel.

The content of vanadium within the specified limits prevents the growth of steel grains in the process of heating for quenching. Wear resistance is enhanced by the formation of fine Vanadium VC type carbides. An increase in the vanadium content of more than 0.25 wt.% Leads to the enlargement of carbides and the rise in price of steel.

The introduction of aluminum and boron leads to the grinding of grain and an increase in toughness. Aluminum within the specified limits increases wear resistance and reduces hardenability. An increase in its content of more than 0.06 wt.% Is undesirable due to a strong decrease in hardenability. A boron content below 0.003% by weight does not provide an increase in toughness and hardenability. An increase in the boron content from 0.003 to 0.007 wt.% In the presence of molybdenum and calcium contributes to an increase in the hardenability of tool steels containing 0.80-1.00 wt.% C, above 0.007 wt.%, Low melting eutectic is formed, which leads to red brittleness.

Calcium has a positive effect on the structural state, increases the impact strength, hardenability (together with boron and molybdenum), improves the processing of steel during cutting.

The compositions of the bottoms proposed and known steels are given in table 1.

The steel is melted in an LP 32-67 induction furnace in a 50 kg crucible. Steel 9XC and ferroalloys were used as the charge. Steel is likewise likewise aluminum in the ladle. Steel was heated to 1630 ± 10 ° C. After steel deoxidation in a crucible, ferrovanadium and molybdenum were introduced into it in special

ampoules that are immersed at the bottom of the furnace. They began to pour the fractional method into ingots weighing 12 kg, which were then subjected to diffusion annealing at 1100 ° C in a protective atmosphere. Annealed ingots were forged onto rods with a section of 15x15 and 20x20 mm in the temperature range from 1140 to 800 ° C with cooling in wells. After that, they were subjected to isothermal annealing: heating to 750 ° C, holding at this temperature until the carbon and alloying elements were uniformly distributed in austenite, cooling at a rate of 35 ° C / h to 550 ° C in the furnace, and holding it to the end austenite, and then air cooling. Hardness after annealing 229 HB. Then, samples were made that were heat treated in the following mode: quenching from a temperature of 870 ° C to oil (heating in a protective atmosphere). Let off at 300 ° C for 1 h followed by air cooling.

Hardness was determined on samples of 10x10x10 mm, impact strength on samples of 10x10x55 mm without a notch on the MK-30 trowel, flexural strength on samples of 10x10x80 mm without a notch on the UMEA-10TM unit. Hardenability was evaluated by the method of end hardening and wear resistance was determined in laboratory conditions on the installation of the MI-1M, operating under the roller-axle scheme, by weight loss on the VLA-200 analytical balance with an accuracy of four digits.

The results of tests of mechanical properties, hardenability and wear resistance are given in table 2.

As can be seen from table 2, the proposed steel has an increased toughness, hardenability and wear resistance, which increases the tool life by 2-2.3 times.

The proposed steel is recommended for woodworking, cutting with heat resistance of 350-400 ° C and die tools operating in automatic mode, as well as large-sized tooling. According to the conditions of operation, the steel should have a high hardness of 60-58 HPVE, with increased impact strength and wear resistance, as well as high hardenability.

Claims (1)

Invention Formula Tool steel containing carbon, silicon, manganese, chromium, molybdenum, vanadium, iron, characterized in that, in order to increase hardenability, toughness and wear resistance, it additionally contains boron, calcium, aluminum in the following ratio components, wt.%: Carbon0.88-0.93 Manganese 0.38-0.42 Silicon1.20-1.24 Chrome0.95-1.05 0.28-0.31 0.18-0.22 0.0028-0.0033 0.08-0.12 0.04-0.06 Else Table 1 table 2