SU1713972A1 - Steel - Google Patents

Abstract

The invention of the otnocits to metallurgy, namely, to cryogenic steel m with improved casting properties. The aim of the invention is to increase the toughness at -253 ° C and the flowability. The steel additionally contains Nickel and nitrogen in the following ratio, wt.%: Carbon 0.03-0,10; chromium 5-15: nickel 0.1-5; manganese 15-30; vanadium 0.1-1.5; boron, 005-0.01; zirconium 0.05-0.15; nitrogen 0.05-0.4; iron - the rest. The use of steel will allow to obtain thin-walled castings up to 5 mm thick. 2 tab.

Description

The invention relates to metallurgy, namely, to cryogenic cast steels having improved casting properties.

Steel (1) is known for operating at cryogenic temperatures. Steel with high strength properties is also known, but it is brittlely destructive at already -196 ° C.

The steel of the chromium-nickel-manganese alloying system, having a high yield strength at 20 ° C (up to 450 MPa) and plasticity {d 60%) has a low impact strength at -196 ° C.

Steel has a high strength in the deformed state ((7 in 500 MPa, ob, 2 300 MPa), however, the impact strength at -196 ° C is low, and in addition, the fluidity of this steel is unsatisfactory and does not exceed 300 mm.

The closest in chemical composition to the claimed steel is steel, having the following composition, wt.%:

Carbon 0.03-0.10

Manganese19-28

5-8

0.8-1.3

0.002-0.007

0.05-0.15

Rest.

This steel has high mechanical properties at operating temperatures up to -196 ° С. However, at -253 ° C, steel has low toughness values. In addition, the fluidity of steel (450 mm) is insufficient to fill thin-walled castings with a thickness of up to 5 mm.

The purpose of this invention is to increase the toughness at -253 ° C and for fluidity. The goal is achieved by the fact that steel containing carbon, manganese, chromium, vanadium, boron, zirconium, and iron additionally contains nickel and nitrogen in the following ratio of components, wt.%: ..

Carbon 0.03-0.10

Manganese15-30

Chrome 5-15

Nickel-1-5

Claims (2)

Vanadium 0.1-1.5 Nitrogen 0.05-0.4 Bor Bor0.005-0.01 Zirconium 0.05-0.15 Iron Others. Nickel doping allows one to maintain a high level of plasticity and toughness at test temperatures down to -25 ° C and to eliminate the embrittlement effect of nitrogen. The positive effect of nickel on fluidity is associated with a decrease in the surface tension of the melt. Nitrogen helps to reduce the liquidus temperature (TL) and increase the fluidity. The introduction of nickel and nitrogen below the specified limits is not effective. Doping with nickel above the specified limit is not economical and furthermore reduces the strength characteristics. The addition of nitrogen in excess of the specified amount leads to an increase in porosity, film formation, and to a noticeable decrease in plastic and viscous properties; moreover, it requires the use of special methods of smelting under pressure, which increases the cost of steel. Mechanical and casting properties were determined on a metal of five pilot melts melted in an open induction furnace, with a capacity of 150 kg, with a base lining. To determine the mechanical properties, standard samples for static tension of 6 mm (GOST 1497-73) and dynamic bending (type II GOST 9454-76) were used. The fluidity is determined by the Néhenji-KuItsova complex casting sample. The chemical composition of the experimental bottoms is presented in table. 1. Mechanical properties and fluidity are given in table. 2. From table. 2 that the steel claimed has a higher toughness than the prototype steel, especially at a test temperature of 253 ° C. The fluidity (Already) of the proposed steel is more than that of the prototype by 30%. The economic efficiency of the proposed invention is as follows: 1. The use of the proposed steel for cast parts of cryogenic machines instead of the known one will make it possible to ensure the filling of thin-walled castings with a thickness of up to 5 mm, which will reduce the scrap. 2. Due to the increase in impact viscosity, the reliability of operation of products from the claimed steel is ensured. When conducting a patent search for cast austenitic steel compositions complexed with nickel and azrt to increase toughness and fluidity, it was not found, therefore, the proposed technical solution has significant differences. Claims of steel Steel, preferably for thin-walled castings, containing carbon, chromium, manganese, vanadium, boron, zirconium and iron, characterized in that, in order to increase the impact toughness at -253 ° C and fluidity, it additionally contains nickel and. nitrogen in the following ratio of components, May.%: Carbon0.03-0.10 Chromium5-15 Nickel0.1-5 Manganese15-30 Vanadium 0.1-1.5 Bor0.005-0.01 Zirconium0.05-0.15 Nitrogen0.05 -0.4 Iron Else T a b l and c a 1 Table 2 The numerator shows -253С. The values of mechanical properties at 20 C. in the denominator - at