SU1108127A1 - Tool steel - Google Patents

Abstract

TOOL STEEL, containing carbon, chromium, molybdenum, vanadium, iron, characterized in that, in order to improve cutting properties and improve processability during the metallurgical processing, it additionally contains titanium, boron and zirconium in the following ratio of components,% by weight: Carbon 0 , 97-1.31 Chromium 3.7 -4.6 Molybdenum 3.0 to 4.0 Vanadium 1.0 -1.5 Titanium 0.7 -1.3 Zirconium 0.001-0.100 BorO, 0002-0, oC IronEstalial g (L with

Description

The invention relates to metal, in particular, to instrumental heat resistant steels used to make cutting tools. Known high-speed steel R6M5 Cl. A disadvantage of the known steel is the relatively high content of scarce alloying elements. Closest to the proposed steel to the technical essence and to the effect of being extinct is tool steel C2 composition, wt. Carbon1.0-1.12 Molybdenum4.7-5.8 Chromium3.6-4.4 Vanadium1.2-1.7 Cerium0.05-0.15 IronErestal The disadvantages of this steel are the relatively low level of cutting properties and low technological properties. plasticity, which does not allow for the manufacture of large-sized tools from it by the method of forging and rolling (ingots made of this steel weighing no more than 700 kg). The purpose of the invention is to increase the cutting properties and improve the processability at the metallurgical industry. This goal is achieved by the fact that tool steel containing carbon, chromium, molybdenum, vanadium, iron, additionally contains titanium, boron, zirconium, in the following ratio of components, wt.%: Carbon 0.97-1.31. Chromium 3.70-4.60 Molybdenum 3.0 -4.0 Vanadium 1.0 -1., 50 Titanium 0.70-1.30 Zirconium 0.001-0.100 Bor0,0002-0.006 IronOther Introduction to the composition of steel titanium leads to the formation of simple Tic type carbides with a hardness of up to 3200 HV, present in the alloy structure in the form of an independent phase component. Titanium carbides are small (5-8 microns) and evenly distributed in the matrix, which provides the proposed steel with high cutting properties. Titanium contributes to the grinding of grains in steel in a cast state and reduces its sensitivity to overheating, due to the fact that refractory titanium carbides retard the combining (growth) of grains. The absence of a developed eutectic in the cast state contributes to an increase in hot plasticity during metallurgical processing, which allows rolling ingots weighing up to 3.5 tons. Fine titanium carbides prevent the growth of austenite grain at a quenching temperature up to 1200-1250 ° C. At these temperatures, due to the dissolution of complex chromium, vanadium, and molybdenum carbides, austenite is additionally doped, and during tempering, secondary hardening due to the release of finely dispersed carbide phases. Fine grain allows maintaining high bending strength (about 300 kg / mm) and impact strength (about 3 kgm / cm). The minimum content of titanium in steel is 0.7%. It is determined by the required level of steel resistance to overheating and the number of carbides that provide the cutting and mechanical characteristics of the material. With an increase in the titanium content in the steel, the amount of TIC increases, and when its content is more than 1.3%, its carbides are located not only inside the grain, but also along the boundaries, forming a continuous mesh. In this case, not only an increase in the carbide phase occurs, but also the aggregation of the carbides themselves, which adversely affects the cutting and mechanical properties of the steel, and the mechanical treatment (grinding, cutting, milling, etc.) is difficult. For this reason, the titanium content is limited (1.3%). The selected interval of 0.7-1.3% provides in steel the optimal combination of all properties and good machinability with its pressure during metallurgical conversion. Introduction to the composition of zirconium steel in an amount of 0.001% and higher contributes to the improvement of plastic properties, since it favorably affects the distribution of sulfide inclusions and. gives them a more round shape. With the introduction of its less than 0.001%, the plastic properties of the steel are not improved. The positive effect of zirconium is up to 0.1%. With a further increase in its content, the level of plastic properties of steel does not increase, therefore, its upper limit is limited to 0.1%. The introduction of boron in steel contributes to an increase in its hardenability, the necessary level of which in the proposed steel is achieved with a minimum content of this element of 0.0002%. Boron, being in solution, is concentrated along the grain boundaries, due to which the austenite increases its tendency to hypothermia, decreases

critical quenching speed and increased hardenability of steel.

The proposed steel after heat treatment in the optimal mode (quenching from temperatures of 1200 ° C and three-time tempering at 550-560 ° C) has the following mechanical properties:

Hardness, HRC 62-64 Durability at

bending, kgf / mm 280-300 Impact viscosity, kgf.m / cm 3 Grain 11-10

Red hardness, HRC (620С, 4 h) 57-58 The chemical composition of the studied melts of the described and known steels is presented in table. one.

The cutting tests were carried out on a 1A62 turning-cutting machine with a stepless adjustment of the speed when turning 1X18H9T steel without using - lubricating cooling fluid with cutting modes V 15M / MIN, S 0.11 mm / rev; t 1 mm.

Geometry sharpening incisors: -v-l (f otr 8 °; H- 45% - If, A o.

As a criterion of wear, wear on the rear face was taken equal to 0.5 mm.

Tested on 3 cutters of each composition.

Averaged data on the resistance (T) of the proposed steel (smelting 1-3; and known (4) the following, min:

1205

2230

3215

4IBS

The results of comparative tests showed that the lower level of the cutting properties of the proposed steel by 20%

0 higher than the famous. .

Testing of technological plasticity was carried out by rolling on a wedge of cast samples melted in an induction furnace. Sizes of images 5 mm.

Samples were rolled with a change in relative reduction in length from 0 to 70-80% at the DUO-200 mill. Rolling speed 0.23 m / s. Before

0 by rolling the sample was heated in a silicon electric furnace to a temperature of 850, 1050, 1200, and 1150 ° C.

The temperature of the metal in the furnace was recorded using a chromel alumel — a 5th thermocouple embedded in the sample.

At each temperature, 3 samples were rolled.

The test results are presented in Table. 2

0

The annual economic effect from the introduction of the proposed steel is 27 thousand rubles.

Table 1

0.97 0.15 0.15 3.70 3.00 1.00 0.70 Described steel 0.001 0.0002 - Other

Note: There is no damage in all patterns.

Continued table. 2

Claims (1)

TOOL STEEL containing carbon, chromium, molybdenum, vanadium, iron, characterized in that, in order to increase cutting properties and improve manufacturability in the metallurgical process, it additionally contains titanium, boron and zirconium in the following ratio of components, May.%: Carbon 0.97-1.31 Chromium 3.7 -4.6 Molybdenum 3.0-4.0 Vanadium 1.0 -1.5 Titanium 0.7 -1.3 Zirconium 0.001-0.100 Boron 0.0002-0.0060 Iron Rest