SU1686020A1 - High-duty cast iron - Google Patents

Abstract

The invention relates to metallurgy. In order to improve performance under heat conditions, high-strength cast iron containing carbon, silicon, manganese, aluminum, magnesium, cerium and iron additionally contains molybdenum diborides, nickel, barium and one metal from the group containing bismuth and tellurium, with the following ratio of components , wt.%: carbon 2.2-3.8; silicon 1.5-2.45; manganese 0.2-2.5; aluminum 0.2-1; magnesium 0.03-0.07; Nickel 1.21-3.27; molybdenum diborides 0.02-0.28; barium 0.002-0.007; cerium 0.02-0.05; one metal from the group containing bismuth and tellurium, 0.001-0.008, iron - the rest. 2 tab.

Description

The invention relates to metallurgy, in particular to the development of high-strength cast iron with increased operational stability under heat exchange conditions.

The purpose of the invention is to improve the performance properties.

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

The introduction of molybdenum diborides is due to the fact that they are dispersed refractory particles that micro-alloy the metal base and crush the structure, being the centers of crystallization, change the nature of crystallization, which contributes to an increase in toughness, torsion endurance and other dynamic characteristics of mechanical and operational properties. Introducing them to 0.02 wt.% Does not provide a sufficient number of crystallization centers in the melt, substantial comminution of the structure in the castings, and an increase in the dynamic characteristics of the mechanical properties. With an increase in the concentration of molybdenum diborides of more than 0.28 wt.%, The number of crystal lattice defects in the metal base increases, the content of non-metallic inclusions at the grain boundaries, deterioration of the shape factor of graphite inclusions increases, the thermal stresses increase, which reduces the dynamic characteristics of mechanical properties, thermal stability and operational properties.

Nickel is introduced as an effective micro-alloying component, which significantly strengthens the matrix during isothermal exposure, crushing graphite inclusions, ensuring uniformity

About 00 ON About S3

about

structure and increase the dynamic characteristics of mechanical properties, the upper limit of the concentration of nickel (327 May.%) due to a decrease in technological plasticity at a higher content. With a decrease in the nickel concentration of less than 1.21 wt.%, The structure is enlarged, the homogeneity of graphite inclusions, the dynamic strength, the torsion endurance limit and the service resistance decrease.

The metal from the group containing bismuth and tellurium has a eliminating effect on the structure, cleans the grain boundaries, reduces the contamination of pig iron with non-metallic inclusions, increases the fatigue strength during torsion and other dynamic characteristics of mechanical and operational properties. At a concentration of up to 0.001 wt.%, The modifying effect is insufficient, and with an increase in their content of more than 0.008 wt.%, The content of nonmetallic inclusions increases, the technological plasticity, dynamic strength and torsion strength, and service properties decrease.

The boundary parameters of the carbon content (2.2– 3.8 wt.%) And the mold (1.5–2.45 wt.%) Were determined based on the practice of producing high-strength mugs with enhanced dynamic characteristics of mechanical properties and fine-grained structure. With a carbon concentration of more than 3.8 wt.% And silicon over 2.45 wt.%, The torsional endurance limit, impact viscosity, and other dynamic characteristics of the cast iron mechanical properties are reduced, and with a carbon concentration of 2.2 wt.% and silicon, up to 1.5 wt.%, increase chill and thermal stresses, crack resistance, impact toughness, torsion strength and operational durability decrease.

The content of alloying additives (manganese 0.2 g2.5 wt.%, Aluminum 0.2–1.0 wt.%) I is due to a significant increase in technological plasticity and strength and is limited by the limits below which plasticity, torsion strength and the strength properties are insufficient, and above which the porosity, film formation and thermal stresses increase, and the plastic properties and fatigue and torsion strength limit are reduced.

The introduction of barium in the amount of 0.002-0.007 wt.%, Cerium in the amount of 0.02-0.05 wt.% -L magnesium 0.03-0.07 May. % due to their high modifying

efficiency and surface activity, which provide an increase in plastic properties, crack resistance and dynamic characteristics of mechanical and operational properties. When their content is less than the lower limits, the elastic-plastic properties are low. Their content is due to the limits that provide nodular graphite in cast iron and the necessary elastic-plastic properties. With the introduction of barium more than 0.007 wt.%, The content of nonmetallic inclusions in the structure of cast iron increases and the dynamic characteristics of mechanical properties and operational durability under heat exchange conditions decrease.

Experimental smelting of cast irons is carried out by a duplex process of a cupola arc furnace using cast iron, steel scrap and ferroalloys as charge materials. The microalloying of cast iron with manganese nickel NMts 5, aluminum A91, silico-manganese CM-17i and molybdenum diborides MoB13Zh is produced in electric furnaces DC 5 at the end of the melt, and modification with ferrocerium, bismuth metal alloys Bi2, Te1 tellurium, magnesium ligature, and there is a silicone and silicone, and a silicon-silicon metal, B1, tellurium Te1, magnesium ligature, and a silicone. foundry buckets. The cast iron is poured at 1390-1410 ° C. Along with molds for obtaining samples and cast parts, process samples are obtained.

To determine the properties of the cast irons, grate and step technological samples, tests for fluidity, crack resistance, and molds are poured to obtain samples for mechanical tests.

In tab. 1 shows the chemical composition of the cast iron experienced bottoms. The content of components in high-strength cast iron is determined by the method of chemical differentiated quantitative analysis. Impact strength is determined on samples of 55 x 10 x 10 mm with a semicircular notch.

In tab. 2 shows the mechanical and technological properties of high-strength cast irons. Mechanical properties obtained on standard samples after isothermal quenching at 360-370 ° C for 3.6-3.8 hours

As can be seen from the data table. 2, the operational durability under heat transfer conditions when heated to 900 ° C, the dynamic characteristics of the mechanical properties for all cast irons within the proposed composition are greater, and the thermal stresses are lower. than high strength cast iron of known composition.

Claims (1)

Invention Formula High-strength cast iron containing carbon, silicon, manganese, aluminum, magnesium, cerium and iron, characterized in that, in order to improve the performance properties, it additionally contains nickel, barium, molybdenum diborides and one element taken from the group containing bismuth and tellurium, in the following ratio, wt.%: Carbon2.2-3.8 Silicon .1.5-2.45 Manganese Aluminum Magnesium Cerium Nickel Barium Diborids molybdenum One item taken from a group containing bismuth and tellurium Iron 0.2-2.5 0.2-1.0 0.03-0.07 0.02-0.05 1.21-3.27 0.002-0.007 0.02-0.28 0.001-0.008 Else Known 3.6 0.3 Known 0.04 Spreadsheets one 2.2 0.07 1.0 Rest 0.001 0.005 0.008 120 330 352 343 46 870 1360 332 9.6 9.1 10.2 9.7 1420 1407 1353 332 348 336 9.2 9.8 1420 1407 1353 1395 1387 juO. „I .., .- ..