SU1694681A1 - Wear resistant cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of parts for shot blasting apparatuses. The purpose of the invention is to increase the tensile strength, hardness and wear resistance in a heat-treated condition. New cast iron contains wt.%: C 2.9-3.3; SI 0.01-0.2; Mp 0.2-0.6; Cg 21-28; B 0.005-0.05; Ca 0.005-0.05; Ti 0.4-1.0 and Fe else. Additional input to the proposed titanium cast iron, as well as a change in the content of SI and Mn, made it possible to increase the CGB 1.25-1.4 times; HRC is 1.05-1.10 times and wear resistance is 1.32-1.38 times. 2 tab.

Description

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The invention relates to the field of metallurgy, in particular, and to the development of the composition of cast iron for the production of parts for shot-blasters.

The purpose of the invention is to increase the tensile strength, hardness and wear resistance.

The invention is illustrated by examples of specific applications.

The choice of boundary limits for the content of components in the iron of the proposed composition is due to the following

The carbon content (2.9-3.3%) is close to the eutectic. If the carbon content is less than 2.9%, the wear resistance decreases due to a decrease in the number of reinforcement phases. Increasing the carbon content of more than 3.3% violates the homogeneity of the cast structure, which leads to a decrease in wear resistance

Silicon (0.01-0.2%) and manganese (0.2-0.6%) are not specifically introduced into the composition of cast iron, but are unavoidable additives that fall with charge materials. Silicon reduces hardenability, especially when its content is more than 0.2%. The silicon content in the pig iron is less than 0.01% difficult to achieve using conventional charge materials, as well as the manganese content less than 0.2%. wear resistance.

Chromium (21.0-28.0%) is required for the formation of wear-resistant carbides of the type (Cr, Fe) C3 and C 2 C 3. When the chromium content is less than 21%, carbides of the type (Fe, Cr) C are formed, which reduce the abrasive wear resistance

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When the content of chromium is more than 28%, large and fragile Crbides of type M2zSb are present in the structure of cast iron. also reduce abrasive wear resistance.

The introduction of calcium to iron (0.005-0.05%) is based on its ability to interact with sulfur. With a sulfur content of up to 0.03%, up to 0.05% calcium is sufficient for complete desulfurization. Calcium contributes to the uniform distribution of non-metallic inclusions in the volume of the casting and to obtain a more dispersed and homogeneous cast structure. The calcium content of less than 0.005% has little effect on the dendritic structure of the cast iron and the morphology of non-metallic inclusions and this amount is not sufficient to suppress the harmful effects of sulfur. The calcium content above 0.05% leads to the formation of large non-metallic inclusions that contaminate the alloy and reduce its properties.

Boron (0.005-0.5%), being a surface-active element, strengthens and stabilizes grain boundaries, slows down crystal growth, facilitates the refinement of the structure, which increases the resistance of cast iron under shock load conditions. Boron additive less than 0.005% is not very effective, and more than 0.05% leads to embrittlement, thermal cracking, coarsening of the structure and, consequently, a decrease in abrasive wear resistance.

Titanium (0.4-1.0%) contributes to the grinding of grain, eliminates the columnar structure of the castings, modifies the cast iron, allows to obtain uniform mechanical properties throughout the thickness of the casting, helps to clean the metal from non-metallic inclusions. Shifts the eutectoid point to the right, reducing the amount of perlite and increasing its carbon content.

Titanium contributes to the formation of a eutectoid with a sufficiently high hardness and an increase in the size of its fields, reducing and eliminating cementite eutectic. The combination of these factors leads to an increase in the viscosity of the iron and a decrease in eutectic chipping during wear. The effect of titanium is more effective when introduced together with boron.

When the content of titanium is less than 0.4%, no increase in wear resistance is observed, since titanium nitrides are mainly formed in the structure, but no carbonitrides are formed, which leads to a decrease in wear resistance of cast iron. When titanium carbonate content in the alloy is more than 1.0%, large sizes of titanium are located along the boundaries of austenitic grains, which reduces wear resistance, crack resistance and fluidity.

Application in titanium cast iron is known, but in this cast iron it plays a specific role.

The functional purpose of titanium is that the best properties of cast iron are achieved with complex doping with chromium, boron and titanium due to

carbon balance between austenite and eutectic melt.

In addition, a significant difference is the restriction of the content of silicon and manganese in the iron only

the amount that is introduced with the other charge materials during the smelting process. The less silicon and manganese will be in this iron, the higher its wear resistance. Based on the above, it can be concluded that this technical solution has significant differences.

PRI me R. In an induction crucible furnace with a capacity of 60 kg with the main lining

Whether the experimental compositions of the proposed pig iron and pig iron, adopted as a prototype (Table 1) according to the conventional technology, melted. Boron in the form of ferroboron, titanium in the form of ferrotitanium and calcium in the form of silicocalcium were introduced into

ladle at release of metal from the furnace.

Castings of blades for the shot-blasting chamber were cast from various cast iron compositions. After cooling to room temperature, the blades were subjected to heat treatment according to the mode: normalization at 1050 ° C, holding for 2 hours. Samples were cut from a part of the blades to study the structure, hardness and wear resistance. The remaining blades were mounted on the rotors of shot-blasting chambers, where they underwent industrial tests for resistance under operating conditions.

The microstructure of cast iron is austenite and a chromistocarbide eutectic with carbides of the type CrCr, TIC, (Fe, Cr) C3. The structure after heat treatment of troostmartencil and carbides.

The wear resistance of the samples from the blades was determined according to GOST 23.208-78. Samples from Art. 45 were used as a reference, and abrasive was electrocorundum with grain size 16-P according to GOST 3647-71. Wear was determined from the mass differences of the specimens determined before and after the test. The relative wear resistance is determined by the formula

to -g 9E P Nn Ki-S-9n-Ya-Ke

where is de. Ep is the arithmetic average value of the mass loss of the reference and test samples;

 - density of reference and test materials. .five

The properties of iron known and proposed composition are given in table. 2

As follows from Tables 1 and 2, additional input into the composition of the proposed titanium cast iron and the change in its composition of the contents of SI and Mn allowed to increase about 1.25-1.4 times: HRC - 1.05-1.10 times and wear resistance - 1.32-1.38 times.

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Claims (1)

Claims of wear-resistant cast iron containing carbon, silicon, manganese, chromium, boron, calcium and iron, characterized in that in order to increase the tensile strength, hardness and wear resistance in a heat-treated state, it additionally contains titanium in the following ratio of components % by weight: Carbon 2.9-3.3 Silicon0.01-0.2 Manganese 0.2-0.6 Chrome21-28 Bor0.005-0.05 Calcium0.005-0.05 Titan0.4-1.0 IronErest Table 1 table 2