EA022421B1 - Die steel - Google Patents

Abstract

The invention relates to iron and steel industry, particularly to compositions of steels and alloys used for production of tools for impact hot forming. The die steel for hot forming contains components in the following ratio, wt.%: carbon 0.44-0.52; silicium 0.18-0.40; manganese 0.45-0.75; chromium 0.80-1.20; nickel 1.30-1.70; molybdenum 0.35-0.65; vanadium 0.18-0.25; aluminium 0.02-0.10; titanium 0.04-0.10; boron 0.001-0.003; niobium 0.05-0.13; calcium 0.005-0.06; iron - the rest. The technical result is increased impact toughness of steel and ultimate tensile strength without decreasing hardness of forming accessories.

Description

The invention relates to the field of ferrous metallurgy, in particular to compositions of steels and alloys used for the manufacture of impact tools of hot deformation. The claimed stamped steel can be used in mechanical engineering and the metal industry for the manufacture of forging tools, subjected to hardening to increase the surface hardening.

Known die steels of the type 5XHM, 4XMNFS, 5X2MNF [1], as well as [2], which are used for the manufacture of forming equipment, containing components in the following ratio, wt.%:

carbon 0.50 - 0.60 silicon 0.10-0.40 manganese 0.50-0.80 chromium 0.50-0.80 nickel 1.40-1.80 molybdenum 0.15-0.30 iron rest

The disadvantage of these steels is manifested in low hardness, heat resistance of the hardened surface layer and low impact strength.

Closest to the proposed technical essence and the achieved effect is steel composition [3] with the following ratio of components, wt.%:

carbon 0.46-0.58 silicon 0.18-0.40 manganese 0.45 - 0.75 chromium 0.80-1.20 nickel 1.30-1.70 molybdenum 0.35-0.65 vanadium 0.18-0.25 aluminum 0.01-0.04 titanium 0.02-0.04 boron 0.001-0.003 zirconium 0.02-0.04 iron rest,

The specified source can be considered as a prototype of the claimed invention. The disadvantage of this steel is not enough high toughness and tensile strength at the required hardness, which leads to a significant decrease in the resistance of the forming tooling.

The objective of the invention is to increase the toughness of steel and tensile strength without reducing the hardness of the forming tooling.

The technical result is achieved by the fact that the components of die steel are in the following ratio, wt.%:

carbon 0.44-0.52 silicon 0.18-0.40 manganese 0.45 - 0.75 chromium 0.80-1.20 nickel 1.30-1.70 molybdenum 0.35-0.65 vanadium 0.18-0.25 aluminum 0.02-0.10 titanium 0.04-0.10 boron 0.001 - 0.003 niobium 0.05-0.13 calcium 0.005 - 0.06 iron rest

The decrease in carbon content is associated with the need to increase the toughness of steel

- 1 022421 to ensure the operability of tooling under shock loads, and when the carbon content is less than 0.44%, the safety margin is insufficient, and when the carbon content is more than 0.52%, the toughness sharply decreases.

The specified content of chromium and vanadium creates favorable conditions for the hardening of the metal matrix, which provides maximum short-term strength of steel at elevated temperatures. Moreover, the chromium content of less than 0.8% leads to a significant decrease in the heat resistance of steel, and more than 1.20 begins to reduce strength at temperatures above 500 ° C. Vanadium within the specified limits strengthens the metal matrix by grinding grain.

The introduction of molybdenum, titanium and boron into steel can significantly increase the hardenability of steel, which is especially important for large equipment. Also, titanium greatly reduces grain, makes it less angular, which increases the plastic properties of steel.

Additional alloying with niobium reduces the grain size in steel and increases strength at high temperatures. Calcium provides a decrease in the concentration of internal stresses due to the globulation of non-metallic inclusions and their spherical shape.

The chemical composition of the experimental heats is given in table. one.

Table 1. The chemical composition of the experimental swimming trunks

Melting The content of elements,% FROM δί Mp SG Mo V Νί A1 Τί IN N6 Sa one 0.44 0.40 0.75 0.94 0.65 0.18 1.70 0.10 0.04 0.001 0.05 0.005 2 0.52 0.20 0.45 1.05 0.54 0.20 1.30 0.04 0.10 0.004 0.13 0.06 3 0.52 0.38 0.45 1.20 0.50 0.25 1.32 0.10 0.10 0.004 0.13 0.06 4 0.50 0.28 0.52 0.98 0.46 0.22 1,64 0.05 0.06 0.002 0.10 0.02 5 0.48 0.18 0.60 0.80 0.35 0.18 1,50 0,07 0.08 0.0025 0,07 0.02 proto- type of* 0.56 0.39 0.75 1.00 0.58 0.19 1.30 0.01 0.04 0.002 - -

The sulfur and phosphorus content in all swimming trunks is not more than 0.02 and 0.025 wt.%, Respectively, the rest is iron;

* - zirconium content - 0.02 wt.%

The properties of steels were determined on samples cut from a forged billet from the surface and central part. The samples were subjected to the following heat treatment: quenching at 950 ° С in oil, tempering at 560 ° С for 2 h. Next, diffusion hardening of the surface of the sample was carried out by applying carbonitriding coating followed by heating in an oven at a temperature of 540 ° С.

Heat resistance was assessed by the hardness of steel after 4 h exposure at 640 ° C. The tensile strength was determined on standard shortened samples. Endurance was evaluated by the endurance limit (δ _-1 ) during bending tests with torsion of smooth diffusion-strengthened samples on an MUI-6000 machine with a base of Ν = 10 ⁴ cycles. Impact strength was determined by standard methods, the microhardness of the hardened layer on the device at a load of 0.981 N. The test results are shown in table. 2.

Table 2. Properties of experimental steels

Melting Heat resistance 640 ° C, NKSe 4 h Impact strength, MJ / m ² Tensile strength, σ _Β , MPa Limit stamina σ.ι, MPa Mikrotver- Dost hardened layer, GPA one 43 0.63 1580/1570 1180/1080 10,4 2 44 0.61 1630/1620 1270/1140 10.8 3 45 0.60 1650/1640 1240/1120 10.8 4 44 0.62 1610/1600 1210/1090 10,4 5 43 0.63 1590/1580 1190/1080 10.6 proto- type of 44 0.57 1520/1510 1170/1080 10.3

In the numerator - for the surface, in the denominator - for the center of the workpiece

An analysis of the test results indicates a higher complex of properties of the developed steel, namely, an increase in the viscosity and strength of tooling under shock loads. From the proposed and well-known steel [3], die inserts 200x300x500 mm in size were made for stamping a fork part from 40X steel.

- 2 022421

The test results are given in table. 3.

Table 3. The resistance of the hardened inserts when pressing steel 40X

Steel The number of manufactured parts, thousand, pcs. Declared 6.5 / 10.1 prototype 5.4 / 8.4

In the numerator, the resistance of unstrengthened inserts, in the denominator - reinforced.

An analysis of the results shows that both before and after hardening of the working surface, the tool life of the proposed steel is 20% higher than that of the known [3].

Information sources:

1. Sorokin V.G., Volosnikov A.V., Vyatkin S.A. Marochnik steels and alloys. -M .: Engineering. 1989, 640 p.

2. Poznyak A.A. and other stamped steels. M .: Metallurgy. 1980.244 s.

3. ΒΥ 6728 C1, 2004.

Claims (1)

Hot stamping steel containing carbon, silicon, manganese, chromium, nickel, molybdenum, vanadium, aluminum, titanium, boron and iron, characterized in that it additionally contains niobium and calcium in the following ratio, wt.%: Carbon - 0 , 44-0.52, silicon - 0.18-0.40, manganese - 0.45-0.75, chromium - 0.80-1.20, nickel - 1.30-1.70, molybdenum - 0 , 35-0.65, vanadium - 0.18-0.25, aluminum - 0.02-0.10, titanium - 0.04-0.10, boron - 0.001-0.003, niobium - 0.05-0 , 13, calcium - 0.005-0.06, iron - the rest.