SU1281600A1 - Wear-resistant white cast iron - Google Patents

Abstract

This invention relates to the development of wear-resistant white cast iron compositions. The purpose of the invention is to increase the tensile strength, impact strength and abrasion resistance. Cast iron contains components in the following ratio, wt.X: C 2.4-3.2; Si 0.2-1.0; MP 0.2-0.8; Cr 12-20; V 1-4; Si 0.5-2.4; Ti 0.1-0.4; Ce 0.03-0.08; A1 0.1-1.0; B 0.005-0.08; N 0.01-0.08 and Fe else. The addition of aluminum, boron and nitrogen to the cast iron provides an increase from 590 to 603-680 I-ffla; improvement of impact strength and from 0.3 to 0.8-1.4 kgf-m / cm and an increase in abrasive resistance from 130 to 140-220 hours. Table 2.

Description

(21) 3858556 / 22-02

(22) 02.25.85

(46) 1/7/87. Bul, № 1

(71) Gorky Automobile Plant

(72) M.P.Shebatinov, I.V. Krasilnikov, P.P. Sbitnev and A.A. Kolpakov

(53) 669.15-196 (088.8)

(56) USSR Copyright Certificate No. 259390, cl. C 22 C 37/06, 1967.

Shebatinov M.P. and others. Wear-resistant white cast iron for replacement parts of cleaning equipment. - Foundry, 1985, № 2, p. 7-8.

(54) WEAR RESISTANT WHITE CAST IRON (57) The invention relates to the development of wear-resistant white compositions.

cast iron. The purpose of the invention is to increase the tensile strength, impact strength and abrasion resistance. Cast iron contains components in the following ratio, wt.X: C 2.4-3.2; Si 0.2-1.0; MP 0.2-0.8; Cr 12-20; V 1-4; Si 0.5-2.4; Ti 0.1-0.4; Ce 0.03-0.08; A1 0.1-1.0; B 0.005-0.08; N 0.01-0.08 and Fe else. The addition of aluminum, boron and nitrogen to the cast iron provides an increase from 590 to 603-680 I-ffla; improvement of impact strength and from 0.3 to 0.8-1.4 kgf-m / cm and an increase in abrasive resistance from 130 to 140-220 hours. Table 2.

From the background fine refers to metallurgy, in particular to the development of white iron compositions for castings operating under impact-abrasive wear.

The purpose of the invention is to increase the tensile strength, toughness and abrasion resistance of the thermo-reversed state.

Carbon content and silicon c. These limits ensure a uniform structure with an optimal content of the hardest and most heat-resistant carbides in it, ensuring high durability of the resulting part, and also provides the necessary strength and toughness.

A decrease in the amount of carbon and silicon less than the lower limit leads to an increase in viscosity and a decrease in the hardness of CHRC), not only in a state, but also after heat treatment, and consequently, to a decrease in durability. Increasing them above the upper limit leads to a sharp decline in wear resistance due to the formation of large eutectic carbides in the cast iron structure, as well as doped Me, C cement.

The manganese content is less than the lower limit when the casting is cooled, contributes to the formation of perlite in the cast iron structure. When the manganese content is above the upper limit, the hardness decreases not only in the cast state, but also after heat treatment due to the increased content of residual austenite. Although this leads to an increase in the viscosity of the material, however, resistance, as the main property, is significantly reduced. To ensure high resistance of cast iron to abrasive wear, it is doped with a large amount of chromium and vanadium. The complex alloying of cast iron with these elements in a certain ratio allows obtaining an optimal martensitic-carbide structure after heat treatment with a uniform distribution of solid and temperature-resistant chromium carbides () and vanadium (VC).

The addition of these elements to less than the lower limit (each separately) leads to a change in the structure, i. to. sharp reduction of carbides

and changes in their chemical composition. As a result, the cast iron's resistance to abrasive wear and shock loads drops sharply. When the content of chromium Bbmie 20 wt. in the cast iron structure, a eutectic is formed on the basis of carbide, which is inferior in hardness and heat resistance to carbide Cg C,. One thing

temporarily cast iron acquires bent

to cracking in the cast state and during heat treatment. The addition of vanadium above the upper limit (together with Cr) leads to the formation of a triple eutectic (type A + VC + Cr C) in the cast state.

Moreover, chromium carbide contains other alloying elements, for example, Fe and Mn, which reduce its hardness and resistance to abrasive wear. As a result, the resistance of parts made of high chromium and vanadium cast iron plummets.

The alloying of cast iron with copper results in a homogeneous structure and an increase in thermal conductivity, which is directly related to an increase in wear resistance. Copper content

less than the lower limit does not affect the change in the structure and, consequently, the properties of chromium iron. The addition of this element to the upper limit is impractical, since the copper content of more than 2.5 mCo% with such chemical composition of cast iron, having an impact on the stabilization of austenite, dramatically increases its residual content after quenching, which reduces hardness and wear resistance.

Boron addition increases proc-hp-1 capacity, stabilizes carbides, and also forms fine carbides in the process of crystallization, thereby contributing to the formation of a fine-dispersed iron structure. Boron content less than the lower limit does not have a significant effect on

The structure of chromium cast iron, and above the top causes the formation of thermal cracks, which leads to a sharp decrease in the resistance of the part.

The addition of aluminum and titanium leads to the deoxidation of liquid iron, the formation of fine nitrides and carbides, the improvement of melt properties and the change of crystallization conditions. As a result, chu5 properties are stabilized.

Guna and Govovitsa resistance to mechanical and thermal effects, and hence the wear resistance. In particular, the introduction of aluminum, the chromium deoxidation, leads to the binding of sulfur and nitrogen into refractory fine sulfides and nitrides, as well as to the substitution of carbon in solid solution, increasing the resistance of the matrix to high temperature oscillations. The aluminum content below the lower limit does not change the melt , and if the content is above the upper limit, the metal is contaminated with nonmetallic inclusions, the tendency to impact on the breakdown of chromium carbides and the casting properties are reduced.

The alloying of cast iron with titanium in an amount less than the lower limit leads to the formation of branched primary carbides in the form of dendrites, contributing to a decrease in abrasive resistance. When the content of this element is above the upper limit, great technological difficulties are created in obtaining suitable castings. At the same time, large titanium nitrides of sharply cut shapes are formed, which causes embrittlement of the metal.

However, as established experimentally,. The titanium content of 0.1–0.4 wt.% ensures high strength (6) and wear resistance of cast iron due to the formation of nitrides and carbides, as well as due to alloying of the metal base. An additive to cast iron from 0.01 to 0.08 wt.% Of nitrogen provides, at these concentrations of titanium, a sharp increase in the resistance of the structure to the effects of high temperatures, i.e., the statistical strength and hardness and elastic modulus are directly related to the increase in

0

five ,

five

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abrasion resistance of cast iron.

The nitrogen content less than the lower limit does not ensure the improvement of the properties of alloyed cast iron, and above the upper limit it leads to embrittlement and, consequently, to an increase in impact-abrasive wear.

To refine the melt from impurities, to bind them to the nonmetal. Pivotal inclusions are rounded, remove liquid iron and increase hardness during the hardening process and uniform its thickness across the wall of the casting, as well as reduce the brittleness of the cast iron by cleaning the grain boundaries during crystallization cerium is introduced from non-metallic inclusions. When studying the fracture surface, it was found that nonmetallic inclusions based on cerium, having a size of less than .1 microns of a rounded shape, directly affect the crystallization of the melt, reducing the size of the primary grain.

The introduction of cerium below the lower limit is not sufficiently effective, and above the upper limit it leads to the appearance of intermetallic phases in the metal base, which are located along the phase boundaries, which leads to embrittlement.

Parts cast from the proposed cast iron are not prone to cracking due to the possibility of obtaining an optimal martensitic-carbide structure after heat treatment with uniform distribution of solid and temperature-resistant chromium- and vanadium (VC) carbides.

The compositions of the proposed cast iron and its properties in comparison with the known are given in table. 1 and 2.

Proposed

12.4 0.2 0.2 18.0 1.0 0.5 0.005 0.05 0.07 0.005 0.01

2.4 0.2 0.2 16.0 1.0 0.5 0.005 0.10 0.1 0.01 0.03

Table 1

As follows from the table. 2, the addition of aluminum, boron and nitrogen to the cast iron contributes to an increase in strength, impact toughness and abrasion resistance.

Claims (1)

Invention Formula Wear-resistant white cast iron containing carbon, silicon, manganese, chromium, vanadium, copper, titanium, cerium Continuation of table 1 Table 2 and iron, characterized in that, in order to increase the tensile strength, toughness and abrasion resistance in the heat-treated state, it additionally contains aluminum, boron and nitrogen in the following ratio, wt.%: Carbon Silicon 2.4-3.2 0.2-1.0 128) 600.  0.2-0.8 Cerium 0.03-0.08 Chrome 12-20 Aluminum 0.1-1.0 Vanadium 1-4 Bor0.005-0.08 Copper 0.5-2.4 Nitrogen 0.01-0.08 Titanium 0.1-0.4 5 IronEstal