RU2016131C1 - Steel - Google Patents

Abstract

FIELD: ferrous metallurgy. SUBSTANCE: the steel further comprises aluminium, nitrogen, calcium, zirconium, the ratio of the components being as follows (wt %): 0.35-0.40; 0.50-0.70 manganeses; 0.17-0.37 silicon; 1.40-1.70 chromium; 2.30-2.60 nickel; 0.20-0.40 molybdenum; 0.15-0.25 vanadium; 0.020-0.045 aluminium; 0.005-0.010 nitrogen; 0.005-0.10 calcium; 0.005-0.010 zirconium; and iron, the balance. EFFECT: improved strength with the impact viscosity level maintained. 2 tbl

Description

 The invention relates to ferrous metallurgy and can be used for the manufacture of highly loaded parts with a diameter or thickness of up to 300 mm in power or transport engineering.

 Steel is known (see the Marochnik of steels and alloys edited by V.G. Sorokin, p. 296), the following composition, wt.%: Carbon 0.35-0.42 Manganese 0.50-0.80 Silicon 0.17- 0.37 Chromium 1.00 - 1.50 Nickel 2.75-3.25 Molybdenum 0.30-0.40 Sulfur not more than 0.035 Phosphorus not more than 0.030 This steel contains up to 3.25% of expensive and scarce nickel.

Closest to the invention is steel (see the Marochnik of steels and alloys edited by V. G. Sorokin, p.302), the following composition, wt.%: Carbon 0.33-0.40 Manganese 0.25-0.50 Silicon 0.17-0.37 Chromium 1.30-1.70 Nickel 1.30-1.70 Molybdenum 0.30-0.40 Vanadium 0.10-0.18 Phosphorus and sulfur not more than 0.025
The aim of the invention is to increase strength while maintaining an identical level of toughness.

The goal is achieved by the fact that in the steel containing carbon, manganese, silicon, chromium, nickel, molybdenum, vanadium, aluminum, nitrogen, calcium and zirconium are additionally introduced in the following ratio of components, wt.%: Carbon 0.35-0.40 Manganese 0.50-0.70 Silicon 0.17-0.37 Chromium 1.40-1.70 Nickel 2.30-2.60 Molybdenum 0.20-0.40 Vanadium 0.15-0.25 Aluminum 0.020- 0.045 Nitrogen 0.005-0.010 Calcium 0.005-0.010 Zirconium 0.005-0.010 Iron and other impurities
Introduction to the composition of aluminum in an amount of 0.020-0.045% ensures the formation of dispersed aluminum nitride in steel, which leads to a limitation of the growth of austenite grain and contributes to a significant increase in the mechanical properties of steel. The minimum aluminum content is 0.020%, selected from the condition of ensuring complete deoxidation of the metal, and the maximum aluminum content is 0.045%, selected from the conditions for obtaining the most effective fine particle dispersion, which limits the growth of austenite grain.

 Nitrogen in steel in an amount of 0.005-0.010% increases the stability of austenite and can partially replace nickel, while the yield strength and tensile strength increase. The minimum nitrogen content is 0.005%, their conditions for improving the resistance of austenitic grain to growth upon heating under heat treatment are selected, and the maximum nitrogen content is 0.010%, chosen to provide the necessary hardness. Calcium is used as a refining element for steel deoxidation.

 The minimum calcium content is 0.005%, selected from the condition of the required degree of deoxidation of the metal, and the maximum calcium content is 0.010%, selected from the condition of ensuring the necessary stability against scale formation.

 Zirconium in an amount of 0.005% - 0.010% is introduced as a metallurgical additive for deoxidation and removal of sulfur. The carbon in steel in an amount of 0.35% is selected from the conditions for ensuring a given hardenability. The maximum content is 0.40%, selected to provide high strength. The introduction of manganese in an amount of 0.50% allows to achieve high hardenability. The maximum manganese content is 0.70%, selected to increase the strength and viscous characteristics of the metal. Silicon in steel in an amount of 0.17-0.37% is an active deoxidizer of steel and reduces the sensitivity to overheating. The minimum chromium content is 1.40%, selected to provide the necessary hardenability, and the maximum chromium content is 1.70% selected to maintain strength. The introduction of Nickel in the amount of 2.30-2.60% is selected based on economic feasibility. Molybdenum in steel in an amount of 0.20-0.40% contributes to an increase in hardenability, an increase in toughness and a decrease in the sensitivity of steel to temper brittleness. Vanadium in steel in an amount of 0.15-0.25% increases the degree of hardness of soluble and dispersed hardening, contributes to the grinding of grain.

PRI me R known and proposed compositions of steels were smelted in an induction furnace IST - 16 and a capacity of 120 tons and cast into molds of 50 kg. Experienced ingots were forged on bars with a diameter of 80 mm. The ingots were heated according to the following mode:
planting in a furnace at a temperature of ≅ 800 ^о С to forging temperature; heating to forging temperature by furnace power up to 1200 ^о С; holding at 1220 ^about 4 hours; forging interval 900 ^about -1200 ^about With; cooling workpieces after forging - in the air.

After forging blanks were pre-heat treatment, final heat treatment, which consisted of quenching from a temperature of 850 ^{° C} in oil, and tempering at 600 ^{° C} - cooling air.

 Table 1 shows the chemical compositions of the proposed and known steels, and in Table 2 the mechanical properties of the steels.

Claims (1)

STEEL containing carbon, manganese, silicon, chromium, nickel, molybdenum, vanadium, iron, characterized in that it additionally contains aluminum, nitrogen, calcium and zirconium in the following ratio, wt.%:
Carbon 0.35 - 0.40
Manganese 0.50 - 0.70
Silicon 0.17 - 0.37
Chrome 1.40 - 1.70
Nickel 2.30 - 2.60
Molybdenum 0.20 - 0.40
Vanadium 0.15 - 0.25
Aluminum 0.020 - 0.045
Nitrogen 0.005 - 0.010
Calcium 0.005 - 0.010
Zirconium 0.005 - 0.010
Iron Else

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