SU1686025A1 - Phosphorous cast iron - Google Patents

Abstract

Phosphorous iznostoyky cast iron belongs to metallurgy. In order to increase the contact fatigue life and wear resistance, it additionally contains niobium, chromium and nitrogen in the following ratio, components, wt,%: carbon 3,3 - 4,3; silicon 2.2 - 3.1; manganese 0.5 - 1.5; titanium 0.03 - 0.4; aluminum 0.05 - 0.7; copper 0.05 - 0.7; phosphorus 0.2 - 1.2; calcium 0.01 - 0.5; REM 0.02 - 0.06, niobium 0.0 4- 0.8; chromium 0.05 - 0.38; nitrogen 0.05 - 0.3 and iron - the rest. The brittle strength of cast iron after one hundred heat cycles with heating to 900 ° C is 630 - 645 MPa; wear resistance 0.21 - 0.36 mg; contact-fatigue durability 732 - 795 MPa; The resistance to the formation of a grid of height is 131–161 cycles and a shock viscosity of 65–85 J / cm2. 2 tab.

Description

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The invention relates to metallurgy, in particular, to the development of wear-resistant phosphorous cast iron compositions for cast products operating under conditions of dry friction and shock loads.

The purpose of the invention is to increase the contact fatigue life and wear resistance.

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

Carbon and silicon are the main elements that determine the structure and complex of the properties of cast iron for various purposes, including for work in conditions of high contact loads and intense wear. With a carbon concentration of 3.3–4.3 wt.% And silicon of 2.2–3.1 wt.%, The most favorable conditions are created for the formation of austenitic – bainite structure, the most favorable

to provide high contact endurance and elastoplastic properties. When the concentration of carbon is up to 3.3 wt.% And silicon up to 2.2 wt.%, The content of cementite increases and the content of bainite decreases, the tendency of the pig iron to bainitic transformation decreases, the viscosity decreases, the brittle strength decreases and contact endurance decreases. With an increase in carbon concentration of more than 4.3 wt.% And silicon in excess of 3.1 wt.%, The hardness decreases, the brittle strength, wear resistance and contact endurance.

Additional introduction of niobium increases the hardness and thermal resistance, crushes the structure of the alloyed matrix, which increases the brittle strength and contact endurance of cast iron. When the content of niobium to 0.04 wt.% Increase in these characteristics is insufficient, and with increasing concentration of niobium in excess of

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0.8 wt.% Elongation of isothermal aging during heat treatment of cast iron, austenite concentration increases, bainite content decreases, which leads to a decrease in brittle strength and elastoplastic properties.

The introduction of chromium provides high strength characteristics, increased frictional wear resistance and contact endurance while simultaneously crushing the structure of the metal matrix. When the chromium content is up to 0.05 wt.%, An increase in these characteristics of cast iron is insufficient, and accordingly an increase in the chromium content in excess of 0.38 leads to a sharp increase in the cementite matrix, deterioration of wear-resistant characteristics and an increase in the duration of heat treatment for graphitization of bound carbon.

The microalloying of cast iron with nitrogen is due to the grinding of the austenitic-bainitic structure, increasing its stability, which contributes to an increase in mechanical properties and contact endurance. Its effect begins to manifest itself with a concentration of 0.05 wt.%, And with an increase in the content of more than 0.3 wt.%, The concentration of non-metallic inclusions at the grain boundaries increases, the contact-fatigue durability, the elastic-plastic properties and the brittle strength of cast iron decrease.

The introduction of SEM is due to its high modifying ability while maintaining thermal stability and frictional properties and increasing the strength, contact endurance and plastic properties of cast iron. The concentration of SEM in the iron up to 0.002 wt.% Is insufficient for its modifying and spheroidizing ability. With an increase in its content in excess of 0.006 wt.%, The concentration of non-metallic inclusions in the pig iron increases, the graphite precipitates become larger, the brittle strength and operational durability of cast iron parts decrease.

The concentration of alloying components (phosphorus 0.2 - 1.2 wt.%, Aluminum, 0.05 - 0.7 wt.%, Copper 0.05 - 0.7 wt.%, Manganese 0.5 - 1.5 wt. .%, titanium 0.03 - 0.4 wt.%) provides high strength characteristics, increased frictional wear resistance and contact endurance. With an increase in their concentration above the upper limits, the content of austenite in the structure increases, which reduces the elasto-plastic properties and brittle strength, while the decrease in concentration below the lower limits of the hardness, strength and contact resistance of the iron is insufficient, and wear resistance is significantly reduced.

Example. Experienced iron smelting

Duplex process of the cupola electric furnace. In the cupola, high-carbon iron with a temperature on the trough of 1380 - 1400 ° C is smelted using cast iron and pig iron, iron scrap, return

own production, known and fluorspar. Next, the melt is overheated in electric furnaces up to 1480 - 1490 ° C and the processes of doping and adjusting its chemical composition on the content of the components to the desired value are carried out. Ferroniobium FN650 (GOST 16773-86) containing 3-8 wt.% Aluminum, 0.4-0.5 wt.% Phosphorus and 0.8 - 1.0 wt.% Copper are used as alloying components; ferromanganese nitrided phosphorus FMN55FN (TU 14 - 5 - 5 - 81) and ferrochrome FH25OH (FM TU 5 - 3 - 80). Modification of cast iron is carried out in a scoop by addition of silicocalcium SC - 30, ferroceri and

ferrotitanium.

Table 1 shows the chemical compositions of the cast iron of the experimental bottoms.

Cast iron melt is cast at 1380 -, 1400 ° C in sandy-clayey

forms in raw.

Samples for mechanical testing and casting are heat treated using isothermal aging at 370-410 ° C. Static and

re-static tests are carried out on a machine. Impact strength is determined on samples of type 8 according to GOST 9454 - 78, and brittle strength after 100 cycles of heat cycles with heating to 900 ° C. Fatigue tests are performed on an URM-2000 machine at a loading frequency of 40 Hz.

Table 2 shows the results of mechanical and technological tests of the known and proposed cast irons.

As can be seen from table 2, the proposed cast iron has higher wear-resistance characteristics, brittle strength, contact endurance and strength properties compared with the known phosphorous cast iron. The economic effect of introducing the invention into the national economy for the use of cast iron in cast parts with rapid wear (technological casting equipment, parts of various machines) will be 96,000 rubles a year, thanks to the addition of Mb, Cr and N to its composition. compared to the known increased by 1.05 - 1.1 times the contact-fatigue life and improved 1.62 - 1.86 times the wear resistance.

Claims (1)

Claims of Phosphorus Cast Iron Containing Carbon, Silicon, Manganese, Titanium, Aluminum, Copper, Phosphorus, Calcium, Rare Earth Elements, and Iron, characterized in that, in order to increase contact fatigue life and endurance, it additionally contains niobium, chromium and nitrogen in the following ratio, wt.%: Carbon3.3 - 4.3 Silicon2.2-3.1 0 3 Manganese Titanium Aluminum Copper Phosphorus Calcium Rare earth items Niobium Chromium Nitrogen Iron 0.5- 1.5 0.03 - 0.4 0.05 - 0.7 0.05 - 0.7 0.2 - 1.2 0.01 -0.5 0.002 - 0.006 0.04 - 0.8 0.05 - 0.38 0.05 - 0.3 Else Table 1 table 2