RU2336364C1 - Austenite steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy and can be implemented in machine and instrument building for fabrication of parts and overlaying welding on surface of parts operating under heavy contact loading. Austenite steel contains carbon, silicon, manganese, chromium, nitrogen, molybdenum, vanadium, titanium, copper, nickel tungsten, boron and iron at a following ratio of elements, wt %: carbon 0.42-1.70, silicon 0.45-4.51, manganese 7.8-20.2, chromium 12.5-20.9, nitrogen 0.17-0.51, molybdenum 0.05-0.22, vanadium 0.03-0.12, tungsten 0.05-0.10, titanium 0.01-0.15, copper 0.20-0.55, nickel 0.23-1.20, boron 0.0010-0.0250, iron - the rest.

EFFECT: there is achieved upgraded abrasive resistance at maintaining significant resistance to adhesive wear and relatively low coefficient of sliding friction.

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Description

The invention relates to the field of metallurgy and can be used in mechanical engineering and instrumentation for the manufacture and surfacing of the surface of parts (sliding bearings, bushings, guides, etc.) operating under severe conditions of contact loading (high loads, intense heating, poor lubrication conditions, the presence of abrasive particles, the presence of a corrosive environment).

Currently, the following analogues of the claimed steel are known.

Austenitic stainless steel, anti-seizing, containing (wt.%):

carbon 0.03-0.10 chromium 14-16 nickel 14-17 manganese 0.5-3.0 silicon 0.4-5.5 nitrogen ≤0.30 phosphorus ≤0.05 sulfur ≤0.05 iron rest

U.S. Patent No. 4,146,412, cl. 148/38 (C22C 38/02, C22C 38/58), claimed 05/30/1978, No. 910484, publ. 03/27/1979.

This austenitic stainless steel contains a small amount of penetration elements - carbon (0.03-0.10 wt.%) And nitrogen (≤0.30 wt.%) And therefore has a low resistance to abrasive wear. Abrasive wear is a very common and intense type of wear that significantly limits the life of many parts and assemblies of machines. It is known that the level of abrasive wear resistance of steels of various classes, including austenitic, strongly depends on the content of interstitial elements in them - carbon and nitrogen, which determine the initial strength of steels and alloys, as well as their ability to strain harden during wear. The low concentration of carbon in the solid solution (austenite) and the small amount of high-strength special carbides in the structure of the analyzed austenitic steel are the reasons for the low surface strength and, accordingly, the intensive wear of this steel under abrasive conditions.

Also known high manganese austenitic chromium stainless steel containing (wt.%):

carbon ≤0.12 silicon 0.1-1.0 manganese 8.0-14.0 chromium 12.0-17.0 nitrogen 0.01-0.30 molybdenum 0.10-0.30 nickel 0.50-3.50 iron rest

Japan Patent No. 53-31811, CL 10 J-172 (MKI C22C 38/58), publ. 09/05/1978. Authors of Co-owner Nobuo, Oaka Kayuki, Arakawa Motohiko, Yamaguchi Yoshinori, Ishida Saki.

Steel is alloyed with a small number of interstitial elements ≤0.12 wt.% Carbon and 0.01-0.30 wt.% Nitrogen, as a result of which its abrasion resistance is low. This limits the scope of the considered steel as a wear-resistant structural material to a relatively small circle of parts, the operation of which excludes the ingress of solid abrasive particles into the friction zone.

Also known is austenitic stainless steel with high scoring resistance, containing (wt.%):

carbon ≤0.15 silicon 2.5-5.5 manganese 6-12 nickel 5-15 chromium 13-25 boron (1-100) × 10 ^-4 and / or calcium (1-100) · 10 ^-4

more than one item in a row:

titanium <2.0 niobium <2.0 cobalt <4.0 tungsten <1.5 iron rest

Japan Patent No. 54-150316, CL 10 J-172 (C22C 38/58), claimed 05/18/1978, No. 55-59573, publ. 11/25/1979.

Steel contains a small amount of carbon and, in addition, there is no nitrogen. Although the steel is alloyed with boron, which has a positive effect on the resistance of steels to abrasive wear, the boron content in the steel is low (1-100) · 10 ^-4 and, therefore, cannot fully compensate for the lack of alloying with carbon and nitrogen, which have a decisive influence on the abrasion resistance of steel surfaces. For this reason, the abrasive wear resistance of the considered steel is small. During friction and wear in the analyzed austenitic steel due to the lack of nitrogen in it, the planar glide mechanism of the dislocation does not receive appreciable development. The planar glide of the dislocation in austenite, as shown by studies of the authors of the proposed application, leads to a significant decrease in the friction coefficient of stainless austenitic steels. The absence of active planar slip of a dislocation in the steel under consideration is the reason for its increased friction coefficient and the intensity of adhesive wear under sliding friction.

The closest in composition to the claimed steel is selected as a prototype austenitic steel (wt.%):

carbon 0.05-0.15 silicon 3.0-5.0 manganese 17-23 chromium 14-18 nitrogen 0.18-0.30 molybdenum 0.05-0.20 vanadium 0.03-0.10 titanium 0.01-0.10 copper 0.25-0.50 nickel 0.25-3.00 iron rest

Patent of the Russian Federation No. 2207397 C2 (MKI C22C 38/58), publ. 06/27/2003 - Bulletin No. 18.

The prototype steel is alloyed with a small amount of carbon (0.05-0.15 wt.%) And nitrogen (0.18-0.30 wt.%), Whose role in the formation of high abrasion resistance steels is extremely large. Because of this, the main disadvantage of the prototype, as well as the above analogues, is its low resistance to abrasive wear. Under real operating conditions of machines, mechanisms, and devices, when solid abrasive particles penetrate from the environment into the contact zone of rubbing steel parts, they accelerate abrasive wear, which ultimately leads to a reduction in the service life of the assembly and the entire product. For this reason, structural materials intended for parts and sliding friction units are also required to have increased abrasive wear resistance. The development of austenitic steels having both high resistance to adhesive and abrasive wear, as well as a reduced coefficient of friction, is, therefore, an urgent and complex material science problem.

The basis of the invention was the task of producing austenitic steel having increased abrasive wear resistance while maintaining significant resistance to adhesive wear and a relatively low coefficient of friction under sliding conditions of steel-steel pairs.

The problem is solved due to the fact that the known steel containing carbon, silicon, manganese, chromium, nitrogen, molybdenum, vanadium, titanium, copper, nickel and iron, additionally contains tungsten and boron in the following ratios of components (wt.%):

carbon 0.42-1.70 silicon 0.45-4.51 manganese 7.8-20.2 chromium 12.5-20.9 nitrogen 0.17-0.51 molybdenum 0.05-0.22 vanadium 0.03-0.12 tungsten 0.05-0.10 titanium 0.01-0.15 copper 0.20-0.55 nickel 0.23-1.20 boron 0.001-0.025

Thus, in comparison with the prototype, the proposed steel has an additional content of tungsten and boron with a certain ratio of components. This confirms compliance with the criteria of the invention of "novelty."

In order to prove the compliance of the invention with the criterion of "inventive step", we consider the distinguishing features of the object and other well-known technical solutions of this section of the technology.

As a result of studies conducted by the authors of the present invention, it was first established that the presence of active planar slip of a dislocation in nitrogen-containing chromomanganese stainless austenitic steels leads to a significant decrease in their friction coefficient and intensity of adhesive wear under dry sliding friction of metal-metal pairs. Subsequent studies by the same authors showed that active planar slip of a dislocation, which causes a decrease in the resistance of the surface layer of plastic deformation in the friction direction, has a negative effect on the abrasive wear resistance of nitrogen-containing low-carbon chromium-manganese austenitic steels. It is known that the abrasive wear resistance of austenitic steels can be significantly increased by increasing the content of elements such as carbon, nitrogen, boron. However, an increase in the carbon content in austenite, which leads to an increase in the energy of stacking faults, impedes the active development of planar slip dislocations in nitrogen-containing stainless austenitic steels. This should help increase the coefficient of friction of the considered steels. The introduction of nitrogen in an amount of more than 0.5 wt.% Is often characterized by an increase in the coefficient of friction of nitrogen-containing chromomanganese stainless austenitic steels. We did not find any literature data on the effect of boron on the development of planar glide dislocation in austenitic steels.

The essence of the invention lies in the fact that the proposed composition of nitrogen-containing stainless chromium-manganese austenitic steel is optimized in such a way that, while maintaining active planar slip dislocation in the austenite, which provides the steel with a low friction coefficient and low adhesive wear intensity, significantly increase the steel resistance to abrasive wear. An increase in the abrasion resistance of nitrogen-containing chromium-manganese austenitic steel is achieved by increasing the content of carbon and nitrogen in it, as well as the introduction of boron and tungsten. In steel hardened from 1100 ° С, carbon is mainly present in the form of special carbides of titanium, vanadium, tungsten, molybdenum and chromium. Part of the carbon (≤0.3%) is in the γ-solid solution. The presence of high-strength special carbides in the steel structure, as well as solid-solution hardening of austenite with carbon, nitrogen, and boron atoms, significantly increase the resistance of austenitic steel to abrasive wear. The presence of nitrogen, chromium, and manganese atoms in a γ-solid solution promotes the development of dislocations in steel during plastic deformation of planar slip.

All of the above ensures compliance of the claimed object with the criterion of "inventive step".

To obtain the inventive steel, ingots weighing 2-50 kg were smelted in an electric furnace in air. The content of sulfur and phosphorus in all alloys did not exceed 0.03% (wt.). The chemical composition of the alloys is given in table 1.

Table 1 The chemical composition of the alloys Alloy number The content of elements, wt.% FROM Si Mn Cr N Mo V Ti W Cu Ni AT one 0.09 4.2 21.5 15,5 0.25 0.15 0.08 0.06 - 0.36 1.9 - 2 0.35 0.32 7.36 12.0 0.11 0.04 0.01 0.01 0.02 0.15 0.15 0,0005 3 0.42 0.45 7.8 12.6 0.17 0.05 0,03 0.01 0.05 0.2 0.23 0.0010 four 0.91 3.2 16.1 16.3 0.27 0.10 0,07 0.08 0,07 0.40 0.60 0,0100 5 1.70 4,51 20,2 20.9 0.51 0.22 0.12 0.15 0.10 0.55 1.20 0.0250 6 1.78 5.50 24.0 22.3 0.55 0.30 0.15 0.22 0.15 0.60 2.00 0,0300

Alloy No. 1 corresponds to the prototype, alloys No. 3, 4, 5 correspond to the claimed steel, alloys No. 2, 6 correspond to steels whose chemical composition goes beyond the alloying of the claimed steel. The ingots were annealed at 1200 ° С for 12 hours and forged into bars with a cross section of 10 × 10 mm. The rods were quenched from 1100 ° C in water. After this heat treatment, the structure of alloys No. 2-6 was austenitic-carbide, and alloy No. 1 (prototype) was austenitic. The microstructure of the austenitic matrix of alloys contained plane accumulations of dislocations — multipoles, indicating that the steels are prone to planar slip. Samples of size 7 × 7 × 20 mm were made from steel rods for friction and wear tests. The steel was tested for abrasion under sliding conditions (reciprocating motion) of the working (end) part of the specimens on the surface of the fixed abrasive - 14A16NM skins (electrocorundum with a grain size of 160 microns). The average sliding speed of the sample was 0.175 m / s, the normal load was 49 N, the length of the working stroke of the sample was 100 mm, the lateral displacement of the skin in one double stroke of the sample was 1.2 mm, and the friction path was 17.6 m. The relative abrasion resistance of the material was determined as the ratio of the weight loss of the armco-iron sample (reference) to the weight loss of the sample of the test material. The weight loss of the samples was measured by weighing on an analytical balance with an accuracy of 0.0001 g. The abrasive wear resistance of the material was determined by the results of 2-4 parallel tests. Testing materials for friction wear under conditions of dry sliding friction (adhesive wear mechanism) was performed under sliding friction of steel pairs in air according to the finger-plate scheme. These tests of austenitic steels were carried out together with steel 45 (plate), heat-treated for hardness of 52-54 HRC (quenching from 850 ° C in oil, tempering 200 ° C - 2 hours). Friction was carried out with the reciprocating movement of the sample (finger) at a speed of 0.07 m / s and a normal load of 294 N. The friction path of the sample was 80 m, the temperature in the friction zone of the pair did not exceed 50 ° C. The wear rate of the samples was calculated by the formula I _h = Q / ρ · L · S, where Q is the sample mass loss, g; ρ is the density of the sample material, g / cm ³ ; L is the friction path, cm; S is the geometric density of the contact, cm ² . The friction coefficient was calculated by the formula f = F / N, where F is the friction force, H; N - normal load, N. The microhardness of the alloys was measured at a load of 1.96 N. The test results are shown in tables 2 and 3.

From table 2 it is seen that the inventive steel (alloys No. 3.4, 5) has 1.4-1.8 times higher abrasive wear resistance than the prototype (alloy No. 1), and also surpasses alloys No. No. in abrasive wear resistance 2, 6.

From table 3 it follows that with dry sliding friction paired with steel 45, when there is adhesive wear of the test pairs, the friction coefficient and wear rate of the inventive steel (alloys No. 3, 4, 5) are almost the same values as the prototype (alloy No. 1). This table also shows that the friction coefficient and wear rate of alloys No. 2, 6 are significantly higher than that of the inventive steel (alloys No. 3, 4, 5).

table 2 Microhardness (N) and abrasion resistance (ε) of alloys Alloy number N, MPa ε one 2600 1.7 2 2800 2,4 3 3300 2.7 four 3550 2.9 5 4200 3.0 6 4250 2.6

Table 3 Wear rate (I _h ) and friction coefficient (f) of alloys when tested in tandem with steel 45 in the mode of adhesive wear Alloy number I _h f one 1.5 · 10 ^-7 0.29 2 2.5 x 10 ^-7 0.31 3 1.5 · 10 ^-7 0.29 four 1.5 · 10 ^-7 0.29 5 1.4 · 10 ^-7 0.28 6 1.7 · 10 ^-7 0.40

Claims (1)

Austenitic steel containing carbon, silicon, manganese, chromium, nitrogen, molybdenum, vanadium, titanium, copper, nickel and iron, characterized in that it additionally contains tungsten and boron in the following ratio of components, wt.%: carbon 0.42-1.70 silicon 0.45-4.51 manganese 7.8-20.2 chromium 12.5-20.9 nitrogen 0.17-0.51 molybdenum 0.05-0.22 vanadium 0.03-0.12 tungsten 0.05-0.10 titanium 0.01-0.15 copper 0.20-0.55 nickel 0.23-1.20 boron 0.0010-0.0250 iron rest