RU2434951C1 - Procedure for manufacture of flat - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: procedure consists in melting steel, in alloying, in out-of-furnace treatment, in tapping steel, in austenisation, in preliminary and finish deformation and in cooling flat to environment temperature. Also, produced steel has the following chemical composition at ratio of ingredients, wt %: carbon 0.17-0.15, silicon 0.40-1.10, manganese 0.60-0.95, chromium 0.30-0.60, nickel 0.20-0.50, copper 0.20-0.60, niobium 0.030-0.060, phosphorus not over 0.015, sulphur not over 0.010, nitrogen not over 0.012 and iron - the rest at value of carbon equivalent Ce not over 0.45 % determined by formula: Ce=[C]+[Mn]/6+([Cr]+[Nb])/5+([Ni]+[Cu])/15 where C, Mn, Cr, Nb, Ni and Cu are weight shares of carbon, manganese, chromium, niobium, nickel and copper. Also, final deformation is performed at temperature 750-950°C. Steel additionally contains titanium at amount of 0.005-0.035 wt %. Depending on requirements of a consumer flat can be normalised or quenched with accelerated tempering.

EFFECT: high quality of flat.

5 cl

Description

The invention relates to ferrous metallurgy, in particular to the production of a new highly efficient type of metal products - rolled steel from low-alloy steel grades 10HSNDA and 15HSNDA of high quality for bridge building and other building structures.

A known method of production of plate for bridge construction for steel grades 10HSND and 15HSND according to GOST 6713-91 (analogue).

The closest in technological essence and the achieved result is a method for the production of plate products, including steel smelting, alloying, after-furnace treatment, steel casting, austenitization, preliminary and final deformation to the required sheet metal sizes and cooling (RF patent No. 2048541, IPC ⁶ C21D 8 / 00, prototype).

The main disadvantages of the known methods (analogue and prototype) are the insufficiently high level of ensuring the strength and plastic properties of rolled products for bridge construction, as well as the inability to provide new consumer requirements.

The task to be solved by the claimed invention is directed, is the industrial production of plate products from low-alloy steel grades 10KHSNDA and 15KHSNDA for bridge construction, providing all the technical requirements of Euronorm:

- impact strength on samples with a sharp notch at temperatures up to -40 ° C;

- continuity of sheet metal according to the results of ultrasonic testing (0, 1, 2 classes of GOST 22727);

- weldability of hire;

- the level of strength and plastic properties in the direction of the thickness of the rolled sheet σвz≥0.75σв; ψz≥20%.

The technical result achieved by the implementation of the invention is to increase the impact strength and cold resistance of sheet metal from low carbon low alloy steels for bridge building and other building structures.

To solve the problem with the achievement of the specified technical result in a known method for the production of sheet metal, including steel smelting, alloying, after-furnace treatment, steel casting, austenitization, preliminary and final deformation and cooling of sheet metal to ambient temperature, according to the proposed method, steel is melted of the following chemical composition, wt.%:

Carbon 0.07-0.15 Silicon 0.40-1.10 Manganese 0.60-0.95 Chromium 0.30-0.60 Nickel 0.20-0.50 Copper 0.20-0.60 Niobium 0,030-0,060 Phosphorus no more than 0.015 Sulfur no more than 0,010 Nitrogen no more than 0,012 Iron Rest,

while providing a carbon equivalent of Ce of not more than 0.45%, determined by the formula: Ce = [C] + [Mn] / 6 + ([Cr] + [Nb]) / 5 + ([Ni] + [Cu]) / 15, where C, Mn, Cr, Nb, Ni and Cu are the mass fractions of carbon, manganese, chromium, niobium, nickel and copper, while the final deformation is carried out at a temperature of 750-950 ° C.

In addition, titanium is additionally introduced into steel in an amount of 0.005-0.035 wt.%.

Depending on the requirements of the consumer, sheet metal can be subjected to normalization or hardening with forced tempering.

After the final deformation and cooling to ambient temperature, the sheet metal can undergo normalization according to the following mode: the sheet metal is heated to a temperature of 950-960 ° C, followed by holding at least 2-2.5 min / mm and subsequent cooling in air to ambient temperature Wednesday.

After the final deformation and cooling to ambient temperature, the sheet metal can be hardened with forced tempering according to the following regime: the sheet metal is heated to a temperature of 950–960 ° C, followed by at least 2–2.5 min / mm and water cooling to a temperature environment, and tempering is carried out for steel grade 10HSNDA at a temperature of 640-750 ° C, for steel grade 15HSNDA at a temperature of 700-740 ° C with a holding time of 1.0-7.5 min / mm and subsequent cooling in air to ambient temperature .

After the final deformation, the rolled sheets are cooled slowly in the temperature range 550-200 ° C with a speed of not more than 0.005 ° C / s and then in calm air to ambient temperature.

The proposed method can be implemented as follows.

Option 1. (Steel 10HSNDA)

Become smelted in an electric furnace. After being released from the furnace, the metal was processed in the ladle and poured on a continuous casting machine, while the alloying of steel with chromium, copper and nickel was carried out due to the partial use of copper-nickel charge materials in the smelting with the addition of ferrochrome, copper and ferronickel during ladle processing. During out-of-furnace metal processing in the ladle, the final metal deoxidation was carried out, its homogenizing gas purging and modifying the silicocalcium treatment. As a result of smelting and after-furnace treatment, steel of the following chemical composition was obtained, wt.%:

Carbon 0.11 Silicon 0.93 Manganese 0.92 Chromium 0.54 Nickel 0.22 Copper 0.42 Niobium 0,039 Nitrogen 0.008 Phosphorus 0.013 Sulfur 0.002 Titanium 0.009 Iron Rest

The carbon equivalent value is 0.42%.

After casting steel on a continuous casting machine, the slabs were stopped for at least 24 hours, subjected to austenitization to a temperature of 1200–1300 ° С, then preliminary and final deformations were performed in reverse mode with a temperature of completion of deformation of 750–950 ° С to obtain sheet metal with a thickness 14 mm

After the deformation process was completed and the temperature reached 450 ° С, the flat products were stacked, when the temperature reached 200 ° С, the stacks were disassembled and the final cooling of the flat products to ambient temperature was carried out in calm air.

Option 1A. After cooling of the rolled sheet to ambient temperature, normalization of the rolled sheet was carried out: it was heated to a temperature of 950 ° C, followed by exposure for 28 min, and cooled in air to ambient temperature.

Option 1B. After cooling the rolled sheet to ambient temperature, it was quenched at a temperature of 960 ° C followed by exposure for 28 minutes and cooled with water to ambient temperature, and then rolled sheet was tempered at 740 ° C with a holding time of 42 min and then cooled in air to temperature the environment.

Option 2 (steel 15HSNDA).

Steel was smelted in an electric furnace. After being released from the furnace, the metal was processed in the ladle and poured on a continuous casting machine, while the alloying of steel with copper and nickel was carried out by using copper-nickel-nickel charge materials for smelting with the addition of ferrous bronze and nickel during ladle treatment. During out-of-furnace metal processing in the ladle, the final metal deoxidation was carried out, its homogenizing gas purging and modifying the silicocalcium treatment. As a result of smelting and after-furnace treatment, steel of the following chemical composition was obtained, wt.%:

Carbon 0.14 Silicon 0.58 Manganese 0.79 Chromium 0.52 Nickel 0.21 Copper 0.22 Niobium 0,042 Nitrogen 0.011 Phosphorus 0.013 Sulfur 0.003 Titanium 0.012 Iron Rest

The carbon equivalent value is 0.41%.

After casting steel on a continuous casting machine, slabs with a temperature of at least 350 ° C were subjected to austenitization to a temperature of 1200–1300 ° C, then in the reverse mode, preliminary and final deformations were performed with a temperature of completion of deformation of 750–950 ° C to produce sheet metal with a thickness of 14 mm

After the deformation process was completed and the temperature reached 450 ° С, the flat products were stacked, when the temperature reached 200 ° С, the stacks were disassembled and the final cooling of the flat products to ambient temperature was carried out in calm air.

Option 2A. After cooling the rolled sheet to ambient temperature, it was heated to a temperature of 960 ° C, followed by exposure for 28 min, and final cooling in air to ambient temperature.

Option 2B. After cooling the sheet metal to ambient temperature, quenching was carried out at a temperature of 960 ° C followed by an exposure of 28 min and cooled with water to ambient temperature, and then sheet metal was tempered at a temperature of 740 ° C with an exposure of 42 min and then cooled in air to ambient temperature.

Analysis of the results of acceptance tests of the mechanical properties of metal samples showed that the developed alloying system and the integrated technology for the production of steel grades 10KHSNDA and 15KHSNDA provided the whole range of qualitative characteristics of rolled products, including additionally standardized ones. At almost the same level of strength and plastic characteristics, the values of impact strength significantly exceed the characteristics of rolled steel from grades 10KHSND and 15KHSND according to GOST 6713.

Thus, Ural Steel OJSC has mastered the industrial production of plate products from microalloyed steel grades of a new generation for bridge construction, which meet all the technical requirements of Euronorm. Produced in thicknesses of 8-50 mm, sheet steel of 10KHSNDA and 15KHSNDA steels with a low content of harmful impurities and non-metallic inclusions reliably provides strength classes C345 and C390 in a normalized state with a guarantee of cold resistance KCV≥29 J / cm ² below -40 ° C.

Claims (5)

1. Method for the production of sheet metal, including steel smelting, alloying, after-furnace treatment, steel casting, austenitization, preliminary and final deformation and cooling of sheet metal to ambient temperature, characterized in that steel of the following chemical composition is obtained at a ratio of ingredients, wt.% :
carbon 0.07-0.15 silicon 0.40-1.10 manganese 0.60-0.95 chromium 0.30-0.60 nickel 0.20-0.50 copper 0.20-0.60 niobium 0,030-0,060 phosphorus no more than 0.015 sulfur no more than 0,010 nitrogen no more than 0,012 iron rest
when the carbon equivalent value of Ce is not more than 0.45%, determined by the formula
Ce = [C] + [Mn] / 6 + ([Cr] + [Nb]) / 5 + ([Ni] + [Cu]) / 15, where C, Mn, Cr, Nb, Ni and Cu are mass the proportion of carbon, manganese, chromium, niobium, nickel and copper, while the final deformation is carried out at a temperature of 750-950 ° C. 2. The method according to claim 1, characterized in that the steel further comprises titanium in an amount of 0.005-0.035 wt.%. 3. The method according to claim 1 or 2, characterized in that after the final deformation and cooling to ambient temperature, the sheet metal is heated to a temperature of 950-960 ° C, followed by an exposure of at least 2-2.5 min / mm and subsequent cooling in air to ambient temperature. 4. The method according to claim 1 or 2, characterized in that after the final deformation and cooling to ambient temperature, the sheet metal is heated to a temperature of 950-960 ° C, followed by an exposure of at least 2-2.5 min / mm and cooling with water to ambient temperature, and then carry out the vacation of sheet metal at a temperature of 640-750 ° C, followed by cooling in air to ambient temperature. 5. The method according to claim 1 or 2, characterized in that after the final deformation and cooling to ambient temperature, the sheet metal is heated to a temperature of 950-960 ° C, followed by an exposure of at least 2-2.5 min / mm and cooling with water to ambient temperature, and then carry out the vacation of sheet metal at a temperature of 700-740 ° C, followed by cooling in air to ambient temperature.