SU1305191A1 - High-strength cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used for castings operating under alternating loads and negative temperatures. The purpose of the invention is to improve the technological properties and the limit of endurance during bending. Cast iron contains, wt%: carbon 3.4-3.8; silicon 1.5-2.6; manganese 0.4-0.7; chromium 0.06-0.2; nickel 0.05-0.8; titanium 0.04-0.6; copper 0.04-0.8; magnesium 0.02-0.08; cerium 0.002-0.08; calcium 0,021-0,04; aluminum 0.002-0.04; zinc 0.02-0.04; lithium 0.006-0.08; strontium 0.002-0.04; iron - the rest. Entering zinc, lithium and strontium in cast iron provides an increase in fluidity from 650 to 740-780 mm at 1400 C, and crack resistance. and tensile strength in bending, table 2. i SL with about SL with

Description

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The invention relates to metallurgy, in particular, to the development of cast iron compositions for castings operating under alternating loads and negative temperatures.

The purpose of the invention is to improve the technological properties and the limit of endurance during bending,

In the proposed iron, the content of the main components is adopted in quantities fO (carbon 3.4-3.8 wt.%, Silicon 1.5-2.6 wt.%, Manganese 0.4-0.7 wt.%) , which provide increased stability of fluidity, reduction of defects in castings. five

Magnesium is contained in the iron in an amount of 0.02-0.08 wt.%, Not reducing the technological properties, impact strength and service properties. The content of cerium and calcium, as modifiers, is based on the practice of producing modified high-strength cast irons with increased wear resistance and fine-grained structure.

Additional introduction of zinc in an amount of 0.02-0.04 wt.% Increases the fluidity and other casting properties, reduces scrap, micro-alloyes 30 metallic base. It dissolves well in the matrix, increases the amount of perlite, increases the dispersion and hardness of cast iron, reduces porosity, which contributes to the improvement of wearability, structural stability, technological and service properties of cast iron. When the concentration of zinc is up to 0.02 wt.%, The microalloying effect and the increase in hardness and stability of properties are weak, and with an increase in the zinc concentration of more than 0.04 wt.%, Chill, shrinkage and burnout decrease, which reduces the stability - Nos foundry and mechanical properties, which leads to a decrease in plastic and service properties.

Lithium in an amount of 0.006-0.08 wt.% Micro-matrixes, increases fluidity, crack resistance, cleansing Q taeT grain boundaries from non-metallic inclusions, increases the stability of technological properties, structure and mechanical properties at negative temperatures. When the content of iti is up to 0.006 wt.%, The micro-doping effect is weak and there is a significant increase in the stability of the technological and mechanical properties at

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negative temperatures are not reached. The upper limit of lithium content is limited by the concentration (0.08 wt.%), At which the number of non-metallic inclusions increases, the processes of segregation increase, since lithium does not dissolve completely into the metal base, which leads to a decrease in toughness, flexural strength and ductility at negative temperatures.

Strontium is introduced into cast iron in an effective modifier additive that provides a significant increase in the technological properties, a decrease in the hardness of the iron and an increase in the stability of the technological properties of the limit of bending and wear resistance. When the content of strontium is up to 0.002 wt.%, The modifying effect is weak, the stability of the technological and service properties is not achieved, and with an increase in the strontium concentration of more than 0.04 wt.%, Segregation increases, the stability of the fatigue endurance limit decreases. stamina.

The concentration of magnesium (0.02-, .0.08 wt.%) And cerium (0.002-0.08 wt.%) Is adopted from the practice of producing high-strength cast irons with improved technological and mechanical properties and is limited to the limits above and below which decreases stability of the structure and properties of cast iron.

The concentration of micro-alloying additives (chromium 0.06-0.2 wt.%, Nickel 0.05-0.8 wt.%, Titanium 0.04-0.6 wt.% And copper 0.04-0.8 wt. %) provides high and stable technological and mechanical properties, hardening and grinding of the metal base, reducing scrap, increasing weldability and density, ensures the stability of the limit of endurance during bending, other mechanical and service properties of cast iron.

Cast iron is smelted in induction furnaces with overheating of the melt up to 1680-1730 Kis using a mixture of pig iron, packaged steel, scrap iron, iron and steel chips, pitch coke, return of its own production and ferroalloys. Additive of lithium, magnesium, metallic cerium, silico-calcium, aluminum, strontium and ferro313

Silicon is conducted into casting buckets. Before entering into the metal, ferroalloys are calcined in a shaft electric furnace at a temperature. The carburizer (coke furnace) is ground in runners to a fraction of 10–15 mm, and the ferroalloys used for modification are crushed in a jaw crusher and screened.

The temperature of cast iron modification in casting buckets is 1630-1710 K. Cast iron is cast in sand-clay foundry molds on a floor conveyor to produce castings, stepped, spiral and wedge technological samples, samples for mechanical tests.

In tab. 1 shows the chemical composition of the cast iron experienced bottoms. The absorption of the components is,%: lithium 53-58, cerium 67-73; magnesium 57-62; calcium 65-72 and zinc 64-69. The fluid flow of iron is determined on spiral process samples.

Mechanical, technological, and service tests were carried out by standard methods, impact viscosity according to GOST 9454-78, and fluidity through a spiral test.

In tab. 2 shows the mechanical and technological properties of the iron of the experimental heats, data on the marriage of the porosity and density of the cast iron in the castings are given.

Carbon

Silicon

Manganese

Chromium

Nickel

Copper

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As can be seen from the table. 2, the proposed cast iron has higher technological properties and an indicator of the flexural endurance strength compared with the known high strength cast iron, which provides an increase in operational durability and reliability under alternating loads.

Claims (1)

Invention Formula High-strength cast iron containing carbon, silicon, manganese, chromium, nickel, titanium, copper, magnesium, cerium, calcium, aluminum and iron, characterized in that it also contains zinc and lithium in order to increase its technological properties and bending fatigue limit. strontium in the following ratio, wt.%: 3.4-3.8 1.5-2.6 0.4-0.7 0.06-0.2 0.05-0.8 0.04-0.6 0.04-0.8 0 , 02-0.08 0.002-0.08 0.021-0.04 0.002-0.04 0.02-0.04 Carbon Silicon Manganese Chrome Nickel Titanium Copper Magnesium Cerium Calcium Aluminum Zinc Lithium Strontium Iron 0,006-0,08 0.002-0.04 Rest Table 1 Continued tabl, 1 Tavpnda2