SU1581770A1 - High-strength cast iron - Google Patents

Abstract

The invention relates to metallurgy, in particular to compositions of high strength cast irons with increased resistance to thermal shocks. The aim of the invention is to increase the operational durability under thermal conditions. The proposed cast iron contains, wt%: carbon 3.2-3.8

silicon 2.6-3.2

manganese 0.2-0.7

nickel 1,4-2,2

vanadium 0.02-0.2

molybdenum 1.1-2.7

chrome 0.03-0.3

boron nitrides 0.03-0.15

tin 0,002-0,1

magnesium 0.03-0.07

aluminum 0.02-0.08

cerium 0.02-0.05

zirconium 0.03-0.15

calcium 0,002-0,027

barium 0.005-0.02

iron else. Cast iron can also be used to make parts that work in friction units at elevated temperatures. 2 tab.

Description

one

(21) 44597W23-02

(22) 07/14/88

(46) 07/30/90. Bul Number 28

(71) Production Association Gomselmash

(72) A.K.Karpov, M.I.Karpenko, G.F.Kovalevsky, E.I. Marukovich, S.M.Badyukova and V.I. Naumenko (53) 669.13.018.8 (088.8)

(56) Patent NDP No. 123606, cl. C 22 C 37/04, 1983.

USSR Author's Certificate No. 924146, cl. C 22 C 37 / U, 1981.

(HIGH-STRENGTH CAST IRON

(57) The invention relates to metallurgy, in particular to compositions of high-strength cast irons with increased resistance to thermal shocks. The purpose of the invention is to increase the operational durability under heat transfer conditions. The proposed cast iron contains, wt%: carbon 3.2-3.8; silicon 2.6-3.2; manganese 0.2-0.7; nickel 1.4-2.2; vanadium 0.02-0.2; molybdenum 1.1-2.7; chromium 0.03-0.3; boron nitrides 0.03-0.15; tin 0,002-0,1; magnesium 0.03-0.07; aluminum 0.02-0.08; cerium 0.02-0.05; zirconium 0.03-0.15; calcium 0.002-0.027; barium 0.005-0.02; iron else. Cast iron can also be used to make parts that work in friction units at elevated temperatures. 2 tab.

with ss

The invention relates to metallurgy, in particular, to compositions of high-strength cast irons used for the manufacture of parts of tooling operating under heat transfer conditions: molds, chill molds, etc.

The aim of the invention is to increase the operational durability under thermal conditions.

High-strength cast iron containing carbon, silicon, manganese, aluminum, nickel, chromium, molybdenum, vanadium, rare-earth metals, tin, calcium, magnesium, zirconium, boron nitrides, barium, cerium and iron in the following ratio of components, ma s. %:

Carbon3,2-3,8

Silicon 2.6-3.2

Manganese 0.2-0.7

Nickel

Zirconium

Molybdenum

Vanadium

Aluminum

Magnesium

Tin

Chromium

Boron nitrides

Cerium

Calcium

Barium

Iron

1.4-2.2 0.3-0.15 1.1-2.7 0.02-0.2 0.02-0.08 0.03-0.07 0.002-0.1

oh oh

0.03-0.15 0.02-0.05 0.002-0.027 0.005-0.02 Else

(lg D

From 00

"VI

Significant differences of the proposed iron are saturated with boron nitrides and the introduction of zirconium and barium and cerium, which significantly increases the resistance of thermal

shocks and performance properties under heat conditions.

The additional introduction of zirconium is due to the fact that it has the effect of grinding and inverting the structure, has a micro-doping effect, increases the stability of the structure under thermal shock conditions and its thermal and operational durability, which provides a significant increase in the resistance of high-strength pig iron to thermal shock. With an increase in zirconium concentration of more than 0.15 masD, the number of crystal lattice defects of the metal base increases, non-metallic inclusions along grain boundaries, the shape factor of graphite inclusions worsens, and thermal stresses increase, which reduces process ductility, crack resistance and thermal resistance. blows. The lower limit of zirconium concentration (0.03 masD) is due to its insufficient micro-doping effect on the structure and the low performance properties of cast iron under thermal shock conditions.

Additional introduction of boron nitrides is due to their modifying effect, improved morphology of the structure, increased elastoplastic properties, thermal stability, which contributes to an increase in the resistance of the pig iron to thermal shock. When the concentration of boron nitrides is up to 0.03 May, the modifying effect and the increase in resistance to thermal shocks are insufficient, and at concentrations of more than 0.15 wPa, the number of nonmetallic inclusions at the grain boundaries increases, the elastic-plastic properties, resistance to thermal shocks and operational resistance decrease. .

Barium improves the stability of the structure, contributes to the hardening of the matrix, cleans the grain boundaries, reduces the contamination of iron with nonmetallic inclusions, serves as surface-active additives, improves the uniformity of the structure, thermal stability, performance and plastic properties. At a concentration of up to 0.005 mA, the modifying effect is insufficient, and with an increase in the content of more than 0.02 mA, the content of non-metallic inclusions increases.

55

five

about

five

and structural heterogeneity, reduced technological plasticity, dynamic strength, thermal resistance and performance properties.

Cerium, to a greater extent than REM, improves the shape factor of graphite, increases the impact strength, heat resistance and plastic properties; which significantly increases the heat resistance and performance properties under heat shock conditions. When the concentration of cerium is less than 0.02%, the modifying effect is insufficient, and with an increase in its concentration of more than 0.05%, the content of nonmetallic inclusions increases and plastic properties and operational durability under heat conditions are observed.

The boundary parameters of carbon content (3.2-3.8 masD) and silicon (2.6-3.2 masD) are determined based on the practice of producing high-strength cast irons with enhanced plastic properties, wear resistance and thermal stability. With a carbon concentration of more than 3.8 masD and silicon more than 3.2 masD, the fatigue strength, thermal resistance, impact viscosity and other mechanical and operational properties of cast iron decrease, and with a carbon concentration up to 3.2 masD and silicon up to 2.6 masD thermal stresses, cracking resistance, thermal resistance, impact strength and other plastic properties in castings are reduced, which reduces the operational durability of cast iron 6 heat exchange conditions when heated to 850 C.

Vanadium is introduced as an effective microalloying and hardening component, reinforcing the effect of grinding the matrix and graphite inclusions, ensuring uniformity of the structure and improving the thermal and operational resistance and elastoplastic properties and their stability. The upper limit of vanadium concentration (0.2 masst) is due to increased chilling, a decrease in the technological plasticity of cast iron and an increase in the tendency to cracks with its higher content, which reduces the operational and elastic-plastic properties. With a decrease in the vanadium concentration of less than 0.02 masd, the structure is enlarged and the dynamic strength decreases,

yield strength, thermal and operational resistance.

The content of alloying additives (manganese 0.2-0.7 wt.%, Molybdenum 1.1-2.7 wt. |, Nickel 1.4-2.2 wt., Chromium 0.03-0.3 wt.%) due to a significant increase in thermal stability, technological plasticity and strength, and limited by the limits below which the heat resistance, technological plasticity and strength properties are insufficient, and above which thermal stresses increase and plastic properties decrease, thermal resistance, flexural strength, impact strength and operational properties.

The introduction of tin in the amount of 0.002-0.1 wt.%, Aluminum 0.02-0.08 wt.%, Calcium 0.002-0.027 wt.% And magnesium 0.03-0.07 wt.% Due to their high modifying efficiency and surface activity, which in these quantities provide cleaning of grain boundaries, increase of plastic properties, crack resistance under conditions of heat changes and technological plasticity. Their content is due to the limits that provide dispersion and uniform structure in castings, nodular graphite in iron and the necessary operational and mechanical properties, as well as a stable pearlitic structure after heat treatment and during operation. As their concentration increases above the upper limits, the operational properties decrease and their waste increases.

Example. Experimental melts are carried out in induction furnaces using cast iron, semi-finished nickel, iron and steel scrap, ferrovanadium, ferromolybdenum, silicon manganese and briquettes of boron nitride, ferrozirconium and other ferroalloys as charge materials. Microalloying of pig iron with ferrovanadium FVd2, ferrozirconium FTsr40, silicon-manganese SMN17 is carried out in an electric furnace at the end of melting at 1500–1520 ° C, and modification with ferricrium (TU 1243-75), boron nitrides FV17N, bar alloys FSBAZO, 94 75), magnesium alloys - directly in dispensing foundry buckets. Stepwise and wedge technology

five

0

five

cue tests. Impact strength is determined on samples of 10 10 55 mm with a semicircular notch.

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 spectral and differential chemical analysis methods. The operational durability is determined by casting Br.05S17 bronze into cast iron metal molds with heating up to 850 C.

In tab. 2 shows data on mechanical and operational properties. The mechanical properties and thermal resistance are determined on standard specimens, and the resistance to thermal shock, heat resistance and wear resistance on specimens cut from castings after tempering at 560-588 ° C.

As can be seen from the table. 2, the heat resistance, wear resistance and resistance to thermal shock of the proposed cast iron are higher than that of the known high-strength cast iron. I

Improving the resistance to thermal shock, wear resistance under dry friction, and the bending endurance limit of the proposed high-strength cast iron will provide increased operational durability of molds and molds operating under heat exchange conditions when casting parts made of copper alloys.

Claims (1)

Invention Formula 0 High-strength cast iron containing carbon, silicon, manganese, nickel, chromium, calcium, magnesium, aluminum, molybdenum, vanadium, tin and iron, 5 characterized by the fact that, in order to increase the operational durability under heat exchange conditions, it additionally contains zirconium, boron nitrides, barium and cerium at the following Q ratio of components, wt.%: Carbon3,2-3,8 Silicon 2.6-3.2 Manganese 0.2-0.7 Nickel1,4-2,2 5 Chrome 0.03-0.3 Calcium0,002-0,027 Magnesium 0.03-0.0 Aluminum 0.02-0.08 Molybdenum1,1-2,7 0 five 0.02-0.2 0.002-0.1 0.03-0.15 0.03-0.15 (Izv.) 3,5 0 {8 1,22,2 O, I 3,20,2 3.6 - O, I, 1 1.8 0.08 2.6 0.002 0.03 0.03 0.2 0.3 0.35 0.2 - 0.06 - °, 03 0.02 1.1 0.02 0.0) 0.02 0.002 0.005 2.8 0.05 0.05 0.05 0.08 0.05 1.8 0.12 O, and 0.03 OJOI5 o | oi2   3.8 0.7 2.2 3.2 0.2 0.10 0.15 0.15 0.08 2.7 0.2 o | h o) o27 o | o2 The cast iron of composition 1 additionally contained 0, May 95 L copper and OO masd REM. 0,005-0,02 0.02-0.05 Else Table 1 0.2 0.3 0.35 0.2 - 0.06 - Other °, 03 0.02 1.1 0.02 0.0) 0.02 0.002 0.005, 08 0.05 1.8 0.12 O, And 0.03 OJOI5 o | oi2 table 2