SU1454873A1 - Cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of castings operating under conditions of friction and cyclic shock loads. The aim of the invention is to increase the shock-fatigue life while maintaining the level of wear resistance. New cast iron contains, wt%: C 3.2-4.5; Si 2-2,8; Mp 0.1-0.4; Cr 0.6-1.2; Cu 0.8-1.4; Mo 0.6 - 1.0; V 0.2-0.6; P 0.2-0.6; N 0.01-0.02; БЬ 0,02-0,04; Mb 0.4-0.8; РЗК 0,005-0,01 and Fe the rest. Additional input into the composition of cast iron Sb, Nb and RZK provided compared with the known composition of the impact-fatigue life of 1.36-1.56 times while maintaining the level of wear resistance of cast iron. 2 tab.

Description

one

The invention relates to metallurgy, in particular to the development of cast iron compositions for castings operating under conditions of friction and cyclic loading.

The purpose of the invention is to penetrate impact fatigue life (UL) while maintaining the level of wear resistance.

The choice of the boundary limits of the components included in the composition of the proposed pig iron is due to very careful considerations.

Carbon and silicon: the lower limits (3.2 and 2.0 wt.%, Respectively) are selected on the basis of the processability of the alloy and ensuring its sufficient fluidity. The upper limits (4.5 and 2.8 May.7, respectively) are chosen on the basis of the need to ensure

ten

15

20

required durability and wear resistance

cast iron.

Manganese is a carbide stabilizing element, hardening alloy. However, it does not form its own carbides, and therefore the manganese content is limited to 0.1-0.4 wt.%. Exceeding the manganese content above the upper limit does not lead to a substantial hardening of the alloy.

The presence of chromium in the composition of cast iron in

the range of 0.6–1.2 wt.% provides the alloy crystallization according to a metastable diagram with the formation of a lebourite eutectic. Chromium refers to strong carbide-forming elements that significantly increase the hardness and wear resistance of the cast iron. The lower limit of the chromium content (0.6% by weight) is due to the absence of

S

00

with

3 of the effect of increasing hardness, the upper (1.2 May.%) Is limited by a decrease in fluidity and an increase in the tendency of the pig iron to be foamed.

Copper in the composition of cast iron causes a dispersion-hardening effect, which contributes to the grinding of pearlite-cementite eutectic. The lower limit of copper content (P, 8 wt. Minimum concentration, vyzatr; and the effect of dispersion hardening. The upper copper content in the cast iron (1.4 wt.%) Is limited by stabilization of dispersion hardening and a slight increase in the ULA alloy. Molybdenum and vanadium are reinforcing , the action of which is associated with the grinding of graphite inclusions, stabilization of the pearlite component of the structure by increasing the dispersion and microhardness of perlite. The content of molybdenum and vanadium is below the lower limit (0.6 wt.% and

: 0.2 wt.%) Leads to a sharp decrease in the strength characteristics, and their content above the upper limit (1.0 wt.% And 0.6 wt.%) Is economically impractical.

Antimony stabilizes the pearlite component of the iron structure, also contributes to the supercooling of the melt, changes the shape and size of graphite inclusions. The total number of inclusions of graphite with the addition of antimony increases, which is favorable for increasing the wear resistance of cast iron. The upper limit of the content of antimony (0.04 wt.%) Is limited by a small increase in the perlitisation effect of the lower (0.02 wt.%) Due to the achievement of the required strength.

Phosphorus significantly increases the fluidity of high-carbon alloys and averages the number of graphite inclusions. The total number of graphite inclusions becomes smaller, but they are located more evenly in the metal base of cast iron. In addition, in the presence of antimony and nitrogen, phosphorus in cast iron forms a complex nitrogen-containing phosphide-antimony lower eutectic, having a greater

by

hardness (E l: 735 kg / mm -), compared with the usual phosphide (HI l 580 kg / mm), which is located at the grain boundaries in the form of a broken mesh and has a higher melting point (),

contributes to the wear resistance of cast iron. A conventional (Fe -) eutectic, having a solid mesh at the grain boundaries, has a low melting point (). During long-term operation, the cast iron is heated to temperatures close to the eutectic melting point, eutectic is melted at the grain boundaries and then a sharp increase in the wear rate, the material is destroyed.

The upper limit of the phosphorus content of 5 (0.6 wt.%) Is limited to the achievement of the maximum hardness of the alloy, the lower limit (0.2 wt.%) Is due to a decrease in the fluidity of pig iron.

The addition of niobium into the composition of wear-resistant cast iron contributes to the refinement of the metal base structure by forming finely dispersed niobium carbides uniformly located along the 5 section of the casting, preventing microloactivity non-uniformity of the alloy. At the same time, the UUD of the chuguka significantly increased.

The lower limit of the content of niobium Q in the pig iron (0.4 wt.%) Is set by the necessary amount of niobium carbides to reduce the microlicational inhomogeneity. The upper limit (0.8 wt.%) Of niobium does not cause a substantial increase in the dispersion of carbides and an increase in the ECU.

The rare-earth metals introduced into the composition of cast iron are referred to as strong refining elements, bind S (iron impurities) to non-metallic inclusions and change the topography of their location, displaced from the grain boundaries and transferred to the inside of the grain. In this case, the forces of molecular-mechanical adhesion significantly increase. The ECM increases due to the removal of non-metallic inclusions from the grain boundaries that prevent dislocation movement. The lower limit of the content of REM (0.005 wt.%) Is the minimum concentration at which its positive effect is realized. The upper limit (0.01 wt.%) Set on the basis of the principle of efficiency. Bbmie the upper limit of the effect of the growth of the CRA and wear resistance is negligible.

Example. The melting of the molten pig iron source was carried out in an induc5

crucible furnace with a capacity of 50 kg with an acid lining of crucibles. After overheating of the melt to 145 ° C, the chemical composition is adjusted to the basic and alloying elements. As ferroalloys used: nitrated ferrochrome PF 400N (Cr 68%, N 5%), ferromanganese FMp 0.5 (85% Mn), ferromolybdenum FM2 (Mo 55%), ferroniobium FN-3 (Nh 55.6%) ferrovanadium Bgl (V 40%), cathode copper MCh, crystalline antimony Cy2, cerium mipmetall MC-40 (Ce 36%).

The assimilation of elements from ferroalloys,%: Cr 65-75; N F, 5-75; Mp 85-90; V 70; Mo 80; 85. The mastery of C 90%, Z 90%, REM 60-70%.

For comparative tests of the known and proposed cast irons at an electronic modulator, a special installation was used that implements one-sided bending of the impact specimen

concentrated blow in the center with a frequency of 400 beats per minute. The impact fatigue test specimens measured 10 10 55 55 mm. The tests were carried out at a constant load of 0.3 kg. The number of load cycles to the destruction of a sample was taken as the criterion of the CRA.

Wear resistance was evaluated by the gravimetric method. A sample with a diameter of 10 mm was moved along the surface of the abrasive material. The dispersion of corundum, which served as an abrasive

material was 250-320 microns. The load on the sample is 1.5 kg. The sample path on the surface was 50 m. The speed of movement was 0.8 m / s.

B table 1 shows the chemical compositions of the proposed and well-known iron, in table 2 - the test results.

Table 1

Famous

Offered lower level 3.2 2.0 0.1 0.6 Average 3.8 2.4 0.25 0.9 - Top 4.5 2.8 0.4 1.2 Table 2

Cast Iron: Limits;

Properties

j wud,

I Wear, g

SredNII

Lower

Sredno

150

1.8 1.4

0.6 0.2 0.2 0.01 0.02 0.4 0.005 Else

0,8 0,4 0,4 0,015 0,03 0,6 00075 Else

1.0 0.6 0.6 0.02 0.04 0.8 0.8 0.01 Else

As can be seen from the obtained test results, the pig iron of the proposed composition is characterized by a higher CF (1.36 - 1.56 times) while maintaining a sufficiently high level of wear resistance.

Claims (1)

Invention Formula Cast iron containing carbon, silicon, manganese, chromium, copper, molybdenum, vanadium, phosphorus, nitrogen and iron, characterized in that, in order to increase impact-fatigue life while maintaining the level of wear resistance, it additionally contains antimony, niobium and rare-earth elements with The following ratio of components, wt.%: Carbon 3.2 - 4.5 Silicon 2.0 - 2.8 Manganese O 1 Chromium. 0.6 - 1.2 714548738 Copper 0.8-1.4 Antimony 0.02 - 0.04 Molybdenum 0.6 - 1.0Niobium0.4 - 0.8 Vanadium 0.2 - 0.6 Rare Earth Phosphorus 0,2-0,65 elements 0,005-0,0 Nitrogen 0.01 - 0.02 Iron Else