SU1447918A1 - High-strength cast iron - Google Patents

Abstract

The invention relates to metallurgy and can be used in the manufacture of crankshafts. The purpose of the invention is to increase the fatigue strength at a temperature in a thermowell condition. cast iron contains wt.%: C 3.3-3-, 9; Si 2.2-3.0; W 0,5HG, 9; P 0.03-0.1; Ni 0.3-2.1; Mo 0.1-0.7; Mg 0.02-0.04; La 0.005-0.008; Nd 0.003-0.006; Ez 0.001-0.003; Yt 0.008-0.010; Na 0.001-0.003 and Fe else. Additional input to the composition of cast iron Nd, Er, Yt and Na provides an increase in the fatigue strength limit at 400 ° C by 1.02-1.1 times. 2 tab. (L

Description

four

WITH

The invention relates to metallurgy, in particular to the development of cast iron compositions for crankshafts.

The goal is to increase the fatigue strength limit at a temperature of 400 ° C. The invention is illustrated with specific application examples.

The choice of boundary limits for the content of components is determined by the following. The introduction of carbon and silicon within the specified limits provides the necessary properties of the proposed high-strength cast iron. The addition of carbon and silicon to cast iron less than the lower limit of the prel leads to bleaching and deterioration in the processability of the resulting castings. An additive above the upper limit leads to an increase not only in the amount, but also in the size of spheroidal graphite inclusions, as well as in the homogeneity of the metal base in the castings, which further reduces the fatigue strength.

The manganese content below the lower limit does not have a significant effect on the properties of cast iron. The introduction of manganese above the upper limit leads to the precipitation of carbides in the cast structure, an increase in hardness and deterioration in workability, and after normalization, an increase in hardness and reduction {fatigue strength, and consequently, a decrease in the durability of the crankshaft.

Phosphorus additive less than the lower limit does not affect the structure and properties of cast iron. The phosphorus content above the upper limit leads to the formation of phosphide inclusions of considerable size, which will require a rise in the modifying elements, and is also accompanied by a decrease in the strength of the properties of the iron.

Doping of high-strength pig iron. On nickel and molybdenum increases the strength properties. This effect is particularly strong when exposed to high temperatures, which is directly related to the formation of a fine-grained cast structure. The introduction of nickel and molybdenum below the lower limit has practically no effect on the change in the structure and mechanical properties of the iron. Nickel addition above the upper limit is inexpedient neither economically nor practically, since its content of more than 2.1% begins to contribute to graphitization and, therefore, to a change in the structure of cast iron. The addition of molybdenum above the upper limit leads to an increase in the amount of carbides during normalization, which dramatically increases hardness and reduces fatigue strength.

Modification of cast iron with a complex of elements ensures uniform

the structure and the correct spherical shape of graphite inclusions are almost the same size. When this occurs, the binding of impurity elements and non-metallic inclusions of regular rounded shape. The interaction of modifying elements with deglobulizers leads to the exclusion of their negative influence on the mechanism of the formation of spherical graphite inclusions.

The presence in the complex modifier of sodium, having a small atomic weight, provides deep purification of the melt from oxygen due to

high affinity and rapid pop-up of oxides. The addition of erbium greatly enhances the process of desulfurization of the melt, which significantly enhances the effect of modifying

drive to almost complete spheroidization of graphite inclusions and their more uniform growth.

The remaining fine-grained non-metallic inclusions during the crystallization of the melt have a significant effect on the formation of the metallic base of cast iron. In particular, being in a melt in a solid state, they perform the role of nuclei, forming

ultimately fine-grained structure. Cleansing the grain boundaries and changing their energy state, modifying elements leads to a significant increase in the strength

characteristics of cast iron in a cast state. In the optimal normalization mode, these properties significantly improve, providing high performance characteristics of the parts.

 The content of the modifying elements (each separately) less than the lower limit is inefficient, since the process of modifying the molten pig iron proceeds in part, and

the upper limit leads to negative results - the process of remodification occurs, i.e. during eutectic crystallization, platelet-shaped graphite inclusions are formed.

Claims (1)

Invention Formula High-strength cast iron containing g carbon, silicon, manganese, phosphorus, nickel, molybdenum, magnesium, hatch and iron, characterized in that, in order to increase fatigue strength, it complements which adversely affect the properties of the cast iron. An example. The smelting of iron is carried out in a DSP-ZA electric arc furnace. The alloying elements — granular nickel and ferromolybdenum — are introduced into the molten iron at 1773-1793 K. Before discharging molten iron from the furnace, lanthanum, neodymium, it contains neodymium, erbium, yttrium, erbium, and sodium are introduced into the bottom of the ladle, modifying triium and sodium in the following ratio are carried out in metallic autoclave. The casting is carried out at 1653-1693 K, crankshafts and samples are cast. Castings are normalized according to the mode: heating at 1133-1213 K, holding for 1 h, cooling in air. The chemical composition of the smelted iron is given in Table 1, the strength characteristics are given in Table 2, from components, wt,%: Carbon3.3-3.9 Silicon Manganese Phosphorus Nickel Molybdenum Magnesium Lanthanum Neodymium 2.2-3.0 0.5-0.9 0.03-0.10 0.3-2.1 0.1-0.7 0.02-0.04 0.005-0.008 p, 003-0,006 which implies that the introduction of Nd, Er, Yt and Na into the composition of the iron ensures that the fatigue strength limit is increased by 1.02-1.1 times. Invention Formula High-strength cast iron containing carbon, silicon, manganese, phosphorus, nickel, molybdenum, magnesium, latchtan and iron, characterized in that, in order to increase fatigue strength, it additionally contains neodymium, erbium, yttrium and sodium at the following ratio 0 is likely to contain neodymium, erbium, yttrium and sodium in the following ratio 5 0 components, wt,%: Carbon3.3-3.9 Silicon Manganese Phosphorus Nickel Molybdenum Magnesium Lanthanum Neodymium Erbium Yttrium Sodium five Iron 2.2-3.0 0.5-0.9 0.03-0.10 0.3-2.1 0.1-0.7 0.02-0.04 0.005-0.008 p, 003-0,006 0.001-0.003 0,008-0,010 0.001-0.003 Rest., Table 1 :Cast iron The content of chemical elements, May, F SiMnSgPNi Mo 1 Cu Ti HsBecl-Hbiu 3.20 2.10 0.04 0.15 Proposed : Cast iron  T . Continuation 1 15 The content of chemical elements, "rac.Z Y La. Nd 1 Cis El stars tt ) 0.12 0.04 0.05 0, 06 Offered 1 2 3 four 0.02 0.006 0.004 0.010-, 0.002 0.002, 04 0.005 0.003 0.008 -, 0.001 0.003, 02 0.00 & 0.006 0.010 - ,, 0.03 0.007 0.005 0.009 0, 003 0.001 0.003 0.003 1.80 0.70 2.0 0.06 . Continued tabl, 1 chemical elements, “rac.Z Y Nd 1 Cis El Na Fe 0.06 Oetal- aoe 0.003 0.001 0.003 0.003 Table 1