RU2643030C1 - Method of production of plates from sparingly-alloy steel with high cold resistance and weldability for wide application, including in arctic conditions - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: steel plate production includes the production of slabs of a given chemical composition with a thickness of not less than 3 times the final thickness of rolled products, austenization of a slab at 1200-1220°C, cooling slabs down to a temperature of 900-950°C, then rolling in a single pass with the deformation of 60-70% to final thickness, followed by cooling in a controlled cooling plant at a speed of 20-80°C/s, or cooling in the water to a temperature of the workshop; not later than in 8-12 hour plates are tempered at a temperature of 640±5°C with a holding time of 8-12 m/mm and cooled in water.

EFFECT: production of rolled steel for critical purposes in thicknesses of up to 50 mm with increased strength, plasticity, viscosity, weldability.

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Description

The invention relates to metallurgy, and more particularly to the production of structural steels with high strength, weldability and cold resistance for use in the construction of offshore structures, transport and heavy engineering, and other industries, including and for working in arctic conditions.

A known method of producing sheet metal from steel of category D, E, F500 of the highest strength according to GOST R52927-2015 [1] - (analog), containing, mass. %: carbon - 0.08-0.12; manganese - 0.45-0.75; silicon - 0.20-0.40; chromium - 1.05-1.30; copper - 0.35-0.65; nickel - 1.85-2.15; molybdenum - 0.10-0.18; aluminum - 0.020-0.060; titanium - not more than 0.02; vanadium - not more than 0.05; niobium - 0.02-0.05; iron is the rest. Steel is produced by multi-pass rolling of cast slabs after heating at 1200-1250 ° C, cooling of the sheets in air or in the foot, followed by hardening with high tempering. The carbon equivalent of steel is 0.74%.

The disadvantage of the analogue is the lack of strength, ductility and toughness at low temperatures.

Closest to the manufacturing technology is a method for the production of sheet metal from steel of the following chemical composition (wt.%): Carbon - 0.04-0.10; Manganese - 0.60-0.90; silicon - 0.15-0.35; nickel - 0.10-0.40; aluminum - 0.020-0.060; vanadium - 0.03-0.05; niobium - 0.02-0.06; iron - the rest; using the thermomechanical processing method (patent RU 2265067. class C21D 8/02, 2005 - prototype), including austenization at a temperature of 1100-1150 ° C, preliminary deformation with a total degree of reduction of 35-60% at a temperature of 900-800 ° C, tempering at 50-70 ° C, final deformation with a total degree of compression of 65-75% at a temperature of 830-750 ° C and accelerated cooling in a controlled cooling installation to temperatures of 500-260 ° C followed by delayed cooling in a caisson to a temperature of no higher than 150 ° C.

The disadvantage of the prototype is the lack of strength and ductility necessary for operation in arctic conditions.

The technical result of this invention is the production of critical products of the following chemical composition:

carbon 0.08-0.10 silicon 0.25-0.35 manganese 0.65-0.75 chromium 0.70-0.90 nickel 0.80-1.00 copper 0.55-0.75 molybdenum 0.25-0.35 niobium 0.02-0.04 titanium 0.001-0.003 vanadium 0.002-0.003 aluminum ≤0.05 sulfur ≤0.003 phosphorus ≤0.004 iron rest

The carbon equivalent of the proposed steel is 0.52-0.57% and significantly lower than the analogue. With greater strength, the proposed steel is characterized by better weldability in comparison with the analogue and in comparison with the prototype is characterized by increased characteristics of strength and ductility.

Steel production technology includes:

- smelting steel of a given chemical composition, manufacturing a workpiece with a thickness of at least 3 times the final thickness of the rolled product, austenizing the workpiece at 1200-1220 ° C, cooling the workpiece to a temperature of 900-950 ° C, then rolling in one pass with a deformation of 60-70% to final thickness, after which immediate cooling is carried out in a controlled cooling installation at a speed of 20-80 ° C / s or cooling in water to the temperature of the workshop;

- no later than after 8-12 hours, leave the sheets at a temperature of 640 ± 5 ° C with a shutter speed of 8-12 min / mm and cool in water.

Increasing the strength of steel is achieved due to intense plastic deformation at the final stage of rolling with a high degree of deformation and the exclusion of structural changes in deformed austenite before quenching.

A distinctive feature of the technology for the production of sheet metal is rolling in one pass on the final steel at a temperature of 900-950 ° C. It is the creation of a fine-grained structure and a large number of defects in the crystal structure and their inheritance with almost no annihilation when converting austenite to martensite.

As a result of the high density of defects in the crystalline structure, their fixing by impurity atoms and uniform distribution due to fixing by microalloying additives, a significant increase in strength, ductility and toughness, as well as, most importantly, weldability of steel due to a decrease in the carbon equivalent and alloying of steel is provided.

The chemical composition of the inventive steel and prototype are given in table. 1, and mechanical properties are shown in table. 2.

Mechanical properties were determined on transverse samples. The static tensile test was carried out on specimens of type III No. 4 GOST 1497, and for impact bending on samples with a V-shaped notch (type II GOST 9454).

In the table. Figure 2 shows the average of the three results of tests for static tensile and impact bending.

Claims (4)

A method for the production of high-strength plate products, including the preparation of steel billets, austenization of the billet, deformation and cooling to ambient temperature, characterized in that the billet is obtained from steel with the following ratio of elements, wt.%: carbon 0.08-0.10 silicon 0.25-0.35 manganese 0.65-0.75 chromium 0.70-0.90 nickel 0.80-1.00 copper 0.55-0.75 molybdenum 0.25-0.35 niobium 0.02-0.04 titanium 0.001-0.003 vanadium 0.002-0.003 aluminum ≤0.05 sulfur ≤0.003 phosphorus ≤0.004 iron rest, the billet is obtained with a thickness of at least 3 times the final thickness of the rolled product, austenization of the billet is carried out at 1200-1220 ° C, cooling of the billet to a temperature of 900-950 ° C, then rolling in one pass with a deformation of 60-70% to a final thickness sheet metal, and cooling is carried out in a controlled cooling installation at a speed of 20-80 ° C / s or in water to the temperature of the workshop, and no later than after 8-12 hours sheets are tempered at a temperature of 640 ± 5 ° C with a shutter speed of 8-12 min / mm and cooled in water.