RU2448184C2 - Wear-resistant cast iron - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: cast iron contains the following, wt %: carbon 2.8-3.3; silicone 2.4-2.8; manganese 0.8-1.5; chrome 0.3-0.7; nickel 0.6-1.3; copper 0.2-0.8; molybdenum 0.2-0.8; aluminium 0.6-1.4; cobalt 0.02-0.28; stannum 0.002-0.015; calcium 0.02-0.05; titanium carbonitrides 0.02-0.25; niobium 0.13-0.30; boron 0.03-0.10; phosphorus 0.02-0.07; lanthanum 0.02-0.07; iron is the rest.

EFFECT: cast iron has high impact strength, service durability at cavitation, wear resistance and corrosion resistance.

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Description

The invention relates to the search for low-alloy cast irons operating under conditions of wear during cavitation, in particular in the manufacture of cylinder liners, bushings and other parts of internal combustion engines with increased operational stability.

Known low-alloyed cast iron (USSR AS No. 734308, IPC C22C 37/10, 1980) of the following chemical composition, wt.%:

Carbon 2.8-3.4 Silicon 2.2-4.0 Manganese 0.05-0.7 Nickel 0.4-1.0 Copper 0.4-1.0 Chromium 0.05-0.4 Calcium 0.003-0.25 Rare earth metals 0.001-0.25 Magnesium 0.01-0.07 Yttrium 0.005-0.25 Phosphorus 0.05-0.3 Iron Rest

Known cast iron has low mechanical properties and high wear during cavitation and fretting corrosion. The operational resistance of sleeves and other parts with intensive wear under cavitation is from 50 to 70 hours.

Also known is wear-resistant low-alloy cast iron (patent PNR No. 102522, IPC C22C 37/08, 1979) containing, wt.%:

Carbon 2.51-3.8 Silicon 1.35-2.49 Manganese 0.40-1.28 Chromium 1.35-1.95 Metals from the group consisting of titanium, calcium, boron, aluminum, antimony and tellurium, in total 0.25-1.20 Copper 0.11-1.49 Iron Rest

This cast iron has high hardness (up to 400 HB) and low plastic properties. Due to the high chromium content in the castings of engine parts, cementite type carbides predominate in the structure, which reduces the toughness and operational resistance during cavitation.

The closest technical solution, selected as a prototype, is wear-resistant cast iron (AS USSR No. 926057, IPC C22C 37/10, 1982), containing, wt.%:

Carbon 2.7-3.2 Silicon 1.2-2.0 Manganese 0.7-1.2 Chromium 0.3-0.5 Nickel 0.6-1.2 Molybdenum 0.3-0.6 Phosphorus 0.02-0.15 Copper 0.30-1.2 Calcium 0.01-0.08 Tin 0.02-0.1 Aluminum 0.05-0.4 Iron Rest

Physico-mechanical properties of this cast iron:

Bending Strength, MPa 840-930 The limit of corrosion fatigue, MPa 315-375 Wear mg / 100 h 51.2-61.4 Damping ability 51-60 Cavitation and operational stability, h 63-75

The disadvantage is low performance in cavitation, difficult stress state and wear.

The objective of this technical solution is to increase operational properties.

The problem is solved in that cast iron containing carbon, silicon, manganese, chromium, molybdenum, copper, nickel, aluminum, phosphorus, tin, calcium and iron, additionally contains cobalt, titanium carbonitrides, niobium, boron and lanthanum in the following ratio of components, wt.%:

Carbon 2.8-3.3 Silicon 2.4-2.8 Manganese 0.8-1.5 Chromium 0.3-0.7 Nickel 0.6-1.3 Copper 0.2-0.8 Molybdenum 0.2-0.8 Aluminum 0.6-1.4 Cobalt 0.02-0.28 Tin 0.002-0.015 Calcium 0.02-0.05 Titanium carbonitrides 0.02-0.25 Niobium 0.13-0.30 Boron 0.03-0.10 Phosphorus 0.02-0.07 Lanthanum 0.02-0.07 Iron Rest

The analysis of the proposed technical solution showed that at the moment there are no known technical solutions in which these differences would be reflected. In addition, these signs are necessary and sufficient to achieve the positive effect indicated in the purpose of the invention. This allows us to conclude that these differences are significant.

The additional introduction of cobalt (0.02-0.28 wt.%) And lanthanum (0.02-0.07 wt.%) Is due to their high chemical and modifying activity in the molten metal, the ability to harden the matrix, grind the structure, improve the shape of graphite and improve mechanical and operational properties. In this case, cobalt to a greater extent affects the elastic-plastic properties and damping ability, and lanthanum strengthens the matrix, improves the shape of graphite, increases the scoring resistance, wear resistance and operational properties. With an increase in their concentration above the upper limits, fumes increase, bleached cast iron, and the stability of damping ability and operational properties decrease. At a concentration of cobalt up to 0.02 wt.% And lanthanum up to 0.02 wt.%, Their modifying and stabilizing effects are insufficient, and the mechanical and operational properties of cast iron are low.

Titanium carbonitrides remove bleaching, accelerate the processes of graphitization and bainitic transformation, grind the structure, increase the damping ability, the limit of corrosion fatigue and operational properties. When they are introduced in an amount up to 0.02 wt.%, The refinement of the structure and increase in mechanical and operational properties are insignificant, and with an increase in their concentration of more than 0.25 wt.%, The amount of carbonitrides along the grain boundaries increases, the uniformity of the structure, and the mechanical and operational properties decrease.

The introduction of niobium (0.13-0.30 wt.%) And boron (0.03-0.10 wt.%) Is due to their high microalloying effect on the structure while stabilizing the elastic-plastic and operational properties. Their effect begins to affect with a concentration of 0.13 wt.% And 0.03 wt.%, Respectively, and with an increase in their content of more than 0.30 wt.% And 0.10 wt.%, The whitening in the thin walls of cast parts increases, decrease mechanical and operational properties.

Calcium is introduced as an effective modifier that cleans grain boundaries from non-metallic inclusions and increases the stability of the structure and operational properties. The upper limit of calcium concentration is due to its limited solubility in perlite, and at a concentration of up to 0.02 wt.% The modifying effect is insufficient.

The introduction of chromium (0.3-0.7 wt.%) Chromium and (0.002-0.015 wt.%) Tin microalloys and strengthens the structure, improves the distribution of graphite and nonmetallic inclusions, increases the density of cast iron, resistance to wear and cavitation, which increases operational properties. Microalloying effect begins to affect with a concentration of 0.3 wt.% Chromium and 0.002 wt.% Tin. With an increase in their content above the upper limits, the bleach increases, and the elastic-plastic and operational properties decrease.

The content of the main components (carbon 2.8-3.3 wt.%, Silicon 2.4-2.8 wt.% And manganese 0.8-1.5 wt.%) Were determined experimentally taking into account the practice of manufacturing wear-resistant cast irons for parts engines with enhanced characteristics of cavitation resistance and damping ability. An increase in their content above the upper limits reduces the uniformity of the structure, the limit of corrosion fatigue, and the stability of mechanical and operational properties. When their concentration is less than the lower limits, the graphitization process worsens and the characteristics of damping ability, plastic and operational properties decrease. With a decrease in carbon content of less than 2.8 wt.% And silicon less than 2.4 wt.% And an increase in the concentration of manganese more than 1.5 wt.% And chromium more than 0.7 wt.%, The whitening increases significantly, in the structure are cementite die casting and mechanical and operational properties, stability of structure and properties are reduced.

The phosphorus content in the composition of cast iron is reduced to 0.02-0.07 wt.%, Because at higher concentrations it reduces the stability of the structure and damping ability, tensile strength in bending and plastic properties.

Molybdenum (0.2-0.8 wt.%), Copper (0.2-0.8 wt.%) And nickel (0.6-1.3 wt.%) Strengthen the metal base and increase the mechanical properties, cavitation - operational stability, accelerate bainitic transformation. The increase in the content of these alloying components above the upper limits reduces the uniformity of the structure, toughness and service life. When their concentration is lower than the lower limits, hardening of the metal base, wear resistance and operational properties are insufficient.

The introduction of aluminum into the melt (0.6-1.4 wt.%) Is based on its high affinity for oxygen and sulfur, an effective microalloying effect, stabilizing the values of the corrosion fatigue limit, physicomechanical and operational properties. Its lower limit (0.6 wt.%) Is due to a marked increase in the stability of the structure, mechanical and operational properties, starting from this concentration. With an increase in aluminum concentration of more than 1.4 wt.%, The content of non-metallic inclusions in the structure increases and the plastic and operational properties decrease.

Cast iron is smelted in open induction furnaces. As charge materials, steel scrap, electrode breakdown, shavings, foundry and pig iron, briquettes of ferroniobium, cobalt K2 (GOST 123-87), briquettes of titanium carbonitrides, ferroboron and other ferroalloys, microalloying and modifying additives are used. Ferromolybdenum, cobalt, nickel, ferroboron, ferroniobium and ferrochrome are introduced into the electric furnace, and the crushed additives of titanium, lanthanum, silicocalcium, tin and other modifying additives in the form of pressed exothermic tablets with a diameter of 50 mm and a height of 50 mm based on aluminum and iron oxides are introduced into ladle for the production of cast iron with a temperature of 1460-1480 ° C. Casting molds are cast at a cast iron temperature of 1400-1430 ° C.

Table 1 shows the chemical compositions of cast irons of experimental swimming trunks. Castings of cylinder sleeves are produced by the method of casting in a chill mold, technological samples and samples for mechanical testing in sand casting molds. Castings and samples are subjected to heat treatment - isothermal aging at a temperature of 350-410 ° C.

Table 2 shows the mechanical and operational properties of the cast iron of experimental melts (compositions 2, 3 and 4 - the proposed wear-resistant cast iron).

The bending strength, toughness and corrosion fatigue limit are determined according to standard methods on samples cut from test castings according to GOST 7293-85, and the operational resistance to cavitation and wear resistance on parts and specimens cast in a chill mold using special stands. The amount of bleach is determined on wedge samples. The mechanical and operational properties are determined after heat treatment of standard samples and engine castings. Impact strength was determined on samples of 10 × 10 × 55 mm with a semicircular notch.

As can be seen from table 2, the proposed cast iron has a higher impact strength, operational resistance to cavitation, wear resistance and corrosion resistance than known.

Table 1 Chemical compositions of cast iron experimental swimming trunks Components The content of components, wt.% (Iron - the rest) 1 (Izv.) 2 3 four 5 6 Carbon 3.0 2,8 3.0 3.3 2.6 3.6 Silicon 1,2 2,4 2.7 2,8 2.1 3.2 Manganese 0.8 0.8 1,2 1,5 0.6 1.8 Chromium 0.5 0.3 0.5 0.7 0.2 0.8 Nickel 1,1 0.6 0.9 1.3 0.3 2.0 Copper 0.3 0.2 0.3 0.8 0.1 1,0 Molybdenum 0.6 0.2 0.5 0.8 0.05 1,1 Aluminum 0.4 0.6 0.8 1.4 0.35 2.2 Tin 0.08 0.002 0.005 0.015 0.001 0.06 Cobalt - 0.02 0.12 0.28 0.01 0.35 Titanium carbonitrides - 0.02 0.2 0.25 0.01 0.3 Niobium - 0.13 0.15 0.30 0.10 0.36 Boron - 0,03 0.06 0.1 0.02 0.12 Calcium 0.08 0.02 0,03 0.05 0.01 0.09 Phosphorus 0.12 0.02 0.04 0.06 0.01 0.08 Lanthanum - 0.02 0.05 0,07 0.01 0.1

table 2 Mechanical and operational properties of cast iron experimental swimming trunks Cast iron properties The properties of the composition of cast iron experimental swimming trunks 1 (Izv.) 2 3 four 5 6 Bending Strength, MPa 926 1130 1230 1192 948 986 Impact strength, J / cm ² 16.6 20.8 24.8 21.5 15.4 18.2 Wear mg / 100 g 52 20.1 16,2 19.6 46.0 38.1 The limit of corrosion fatigue, MPa 360 393 405 394 372 383 Operational stability during cavitation, h 73 106 128 112 92 95 The coefficient of wear resistance (standard steel 20 GL) 3.2 9.8 10.6 9.2 4.2 6.8 Fatigue limit, MPa 372 402 428 422 380 362

Claims (1)

Wear-resistant cast iron containing carbon, silicon, manganese, chromium, nickel, molybdenum, aluminum, copper, phosphorus, tin, calcium and iron, characterized in that it additionally contains cobalt, titanium carbonitrides, niobium, boron and lanthanum in the following ratio of components, wt.%:
carbon 2.8-3.3 silicon 2.4-2.8 manganese 0.8-1.5 chromium 0.3-0.7 nickel 0.6-1.3 copper 0.2-0.8 molybdenum 0.2-0.8 aluminum 0.6-1.4 cobalt 0.02-0.28 tin 0.002-0.015 calcium 0.02-0.05 titanium carbonitrides 0.02-0.25 niobium 0.13-0.30 boron 0.03-0.10 phosphorus 0.02-0.07 lanthanum 0.02-0.07 iron rest