SU602595A1 - Steel - Google Patents

Description

(54) STEEL

The invention relates to metallurgy, in particular, to compositions of steels used for large welding and goods, for example, welded rotors with cross sections up to 900 mm, possessing low clingability to brittle fractures and good weldability. Known steel of the following Sovetava, wt.%: 0.2-0.7 Carbon 0.17-0.37 Silicon 0.4-0.7 Manganese. 1.7-2.0 1.2-1.6 Nickel 0.51-1.6 Molybdenum 0.01-0.1 Vanadium 0.02-0.05 Rest of Iron The disadvantage of this steel is limited hardenability, which leads to to structural heterogeneity p section. As a result, in the center of the forging with a section of 900 mm after final heat treatment, the structure is a mixture of decomposition products in the pearlite and upper bainite areas with its characteristic lower level of strength and plastic properties. This is due to the insufficient doping with strengthening elements — nickel and molybdenum. A reduced nickel content also leads to an increase in the cold brittleness threshold, increases segregation and leads to uneven properties. The aim of the invention is to increase the hardenability, strength and viscosity of steel. For this, the proposed steel additionally contains aluminum and calcium in the following ratio of components, wt.%: 0.20-0.28 Carbon 0.4-0.7 Manganese 0.17-0.37 Silicon 1.0-1.5 2 , 55-2.85 Nickel 0.66-0.75 Molybdenum 0.01-0.05 Vanadium 0.02-0.04 Aluminum 0.005-0.05 Calcium Remaining Iron Increase in nickel content to 2.55-2, 85% increase in strength, hardenability, -structural p-uniformity and isotropy of mechanical properties. 8 steel. Nickel, a hardened A-solution of iron, simultaneously weakens the buildup of dislocation by atoms and facilitates plastic deformation, which reduces the risk of brittle fracture. An increase in the molybdenum content to 0.066-0.75% and the lumpy vanadium increases the steel resistance to steel. The introduction of aluminum and the presence of vanadium ensure the complete binding of nitrogen and nitrides, which leads to the grinding of grain and a decrease in the threshold of breakage. . The addition of calcium increases the isotropy of the properties and contributes to a uniform distribution of sulphides, reduces secondary oxidation of steel. The content of sulfur and phosphorus impurities in the proposed steel should not exceed 0.018%. In tab. 1 shows the compositions (1-3) of the proposed and (4) known steel. 10,230,62,71, b10,7 20,250,72,851,350,73 30,270,52,551,50,68 40,220,51,251,70,55

NOTE: Pb is the rest.

1 2 3 4

T. a b l and c a

0.05 0.03 0.008

0.02

Table 2 in the table. 2 shows the mechanical properties of these st.ale, obtained on samples with a cross section of 25 25 mm, a length of 200 mm after heat treatment; normalization at and tempering at, and final heat treatment: quenching from 900 ° С and tempering at 645С. The mechanical properties of the forgings of a section of 900 mm after quenching through water into oil and tempering at 645s are given in Table. 3. The proposed steel is insensitive to overheating: with an increase in austenization temperature from 820 to 5all of grain, it increases from 8-9 to 5-6 points of the NKMZ scale. The change in mechanical properties in the process of increasing the tempering temperature shows good tempering of the steel. The increased strength and toughness of the proposed steel allows it to be recommended for the manufacture of welded rotors of lower power, in particular for the mouth (turbine 1000 mW. 0.280.030.02 0.180.010.04 0.360.050.04 0.180.015

Table 3