Rebar hot rolled steel and the method of steelmaking to obtain

 

(57) Abstract:

The invention relates to metallurgy and can be used in the manufacture of welded hot rolled bar reinforcement class AS for concrete structures. The proposed reinforcement hot-rolled steel that contains components in the following ratio, wt.%: carbon 0,16-0,24, manganese 0.60 and 0.95, and the silicon 0,50-0,90, vanadium 0,12-0,20, chromium not more than 0.20, Nickel not more than 0.15, copper not more than 0.10, iron rest. The temporary resistance to the yield strength of steel is 1,25-1,40. The way of obtaining includes obtaining the intermediate product of natural-doped vanadium cast iron, steel production in steel-smelting unit, flow of molten steel in the ladle deoxidation and alloying his ferroalloys. The melting of steel is produced from solid steel scrap and liquid intermediate product, containing components in the following ratio, wt.%: carbon 3,2-3,7, manganese 0,03-0,1, silicon 0,03-0,1, vanadium 0,03-0,1, chrome 0,03-0,1, phosphorus less than 0.05, sulfur not more than 0.05, iron rest, providing 14-58 wt.% vanadium in steel, and the remaining amount of vanadium is injected in the form of siliconindia in the bucket. The process of deoxidation and alloying of steel in the ladle is carried out at odnovremennaya with a yield strength of at least 500 N/mm2interim resistance of at least 600 N/mm2relative elongation5not less than 14% while reducing its cost by reducing the number of manganese and simplify the production technology. 2 S. and 1 C.p. f-crystals, 3 tables.

The invention relates to metallurgy, in particular to the production technology and the composition of steel, intended mainly for the production of welded reinforcement concrete structures, and can be used in the manufacture of hot-rolled bar reinforcement class AS.

Known weldable hot rolled reinforcing steel GS [1] the following chemical composition, wt.%:

Carbon - 14-0,23

Manganese - 1,20-1,60

Silicon - 0,60-0,90

Chromium - Not more than 0.3

Iron - Rest

The steel has a carbon equivalent in the range of 0.34 - 0.51% of that provides its weldability, but relatively low strength (t300 N/mm2,in500 N/mm2) and corresponds to the class AS. Moreover, in this steel high manganese content, which makes expensive its mass application.

Known thermo-hardened steel TSSP [2] class HAS the following chemical composition, wt.%:

Carbon - 0,14-0,22

types of welding except the bathroom welding. However, it has a low value of the ratio of temporary resistance to the yield strength (1,05 - 1,25), which makes it dangerous its application in mesoamericana reinforced concrete elements due to the possible development of significant deflections and large magnitude of the cracks in the development of valves significant plastic deformations. In the hot rolled condition the steel has a low strength (t235-245 N/mm2,in370-490 N/mm2).

Closest to the present invention is hot-rolled steel [3] the following chemical composition, wt.%:

Carbon - 0,17-0,25

Manganese - 1,0-1,5

Silicon - 2,0-2,5

Vanadium - 0,06-0,12

Chrome - 0.03

Nickel - 0.03

Copper - 0.03

Iron - Rest

the corresponding class AS.

This steel after heat treatment, has high corrosion resistance, due to the high content of silicon. In the hot rolled condition the use of this steel as reinforcement impossible due to the fact that when the upper carbon content of 0.25%) and manganese (1,5%), the formation of hardening structures and, as a consequence, the reduction of plasticity, and in combination with a high content of silicon - deterioration of weldability. In addition toh designs.

There is a method of production of steel [5], according to which in the steelmaking unit smelted intermediate, pre-rascist his mn containing alloys, then Naegleria and microregion vanadium liquid natural-doped vanadium cast iron, in which pre-injected additive in the form of aluminum and finally rascist in the bottling bucket. In natural-doped vanadium cast iron pre-enter additional additive in the form of vanadium slag, prizegiving in the process of cast iron in a container designed for delivery of iron to steel unit in the amount of 1.0 to 13.3% by weight of natural-doped vanadium cast iron.

This production method involves obtaining carbon steel with a carbon content of about 0.8%. This steel cannot be used as a welded reinforcement concrete structures. The disadvantages of the known method of steelmaking are difficulties dosage and filling vanadium cast iron in the ladle and the introduction of vanadium slag vanadium in iron, as well as the fact that a large number of top up with cast iron is difficult to get into the desired chemical composition of the steel. In addition to legirovaniem to the present invention is a method of production of steel [4], according to which in the steelmaking unit smelted intermediate, rascist his mn containing alloys, then Naegleria and microregion vanadium liquid natural-doped vanadium cast iron. Natural-doped vanadium cast iron is poured into steel-making unit in an amount to provide in the intermediate 40 - 60% of the required content of vanadium in the steel, and the remaining amount of vanadium is injected with vanadium slag, pressively in the process of draining of the melt in the ladle.

This method has significant disadvantages: difficulty of dosing and filling of vanadium cast iron in the ladle; use for alloying of steel vanadium slag, which is the raw material for the production of valuable ferrovanadium; half contained vanadium in steel (40 - 60%) is introduced with natural-vanadium alloyed cast iron, used for vanadium slag, and then ferrovanadium.

The technical problem is to obtain well-welded hot rolled steel with yield point not less than 500 N/mm2interim resistance of at least 600 N/mm2relative elongation5not less than 14%, reducing its cost by reducing the number of margana is I hot rolled steel contains carbon, manganese, silicon, vanadium, chromium, Nickel, copper and iron, according to the invention it contains components in the following ratio, wt.%:

Carbon - 0,16 - 0,24

Manganese - 0.60 and 0.95 to

Silicon - 0,50 - 0,90

Vanadium - 0,12 - 0,20

Chromium - Not more than 0.20

Nickel is Not more than 0.15

Copper is Not more than 0.10

Iron - Rest

the ratio of temporary resistance to the yield strength is 1,25 - 1,40.

In the method of steelmaking to obtain a hot rolled reinforcing steel, including the production of the intermediate product from prirodnolegirovannye vanadium cast iron, steel production in steel-smelting unit, flow of molten steel in the ladle deoxidation and alloying his ferroalloys, according to the invention the melting of steel is produced from solid steel scrap and liquid intermediate product, containing components in the following ratio, wt.%:

Carbon - 3,2 - 3,7

Manganese - 0,03 - 0,1

Silicon - 0,03 - 0,1

Vanadium - 0,03 - 0,1

Chrome - 0,03 - 0,1

Phosphorus - Not more than 0.05

Sulfur is Not more than 0.05

Iron - Rest

providing 14-58 wt.% vanadium in steel, and the remaining amount of vanadium is injected in the form of siliconindia in the bucket, the process of deoxidation and alloying of steel in the ladle carrying out the which is the byproduct of the production of ferrovanadium.

The temporary resistance to yield 1,25-1,40 provides improved reliability mesoamericana concrete elements by reducing the likelihood of significant deflections and large magnitude of the cracks in the development of valves significant plastic deformation.

The basic requirements for welded reinforcing steel is a high strength, ductility and weldability, which is provided by a low value of carbon equivalent CEQ< 0,52%. Carbon equivalent is calculated by the formula:

< / BR>
The elements included in the proposed steel form its structure and, being in a complicated relationship, provide the required properties.

When the carbon content is less than 0.16 per cent, significantly reduced the yield strength and tensile strength of steel.

When the carbon content of up to 0.24% reduced plasticity and deteriorates the weldability of steel.

When the content of manganese is less than 0.60% lower yield strength and tensile strength by reducing alloying of steel.

When the content of manganese is more of 0.95%, a decrease of ductility without a significant increase over the other.

When the silicon content more than 0.90% reduced plasticity and deteriorates the weldability of steel.

Introduction vanadium steel gives fine structure, since it forms stable carbides with high temperature dissolution in austenite, so they contribute to the grinding of grain.

Minimum vanadium content of 0.12% was adopted for the formation of carbides in the steel vanadium and provide the desired yield strength and a maximum of 0.20% is determined by the persistence of high ductility and weldability.

The chromium content of up to 0.20% provides high ductility and weldability.

The Nickel content of more than 0.15% leads to an increase in the cost of steel without any appreciable increase its mechanical properties.

The copper content of more than 0.10% contributes to the aging of steel.

The proposed method in the steelmaking unit of molten steel from a vanadium-containing intermediate (after devanagiri vanadium cast iron), which allows to simplify the technology, eliminating the difficulties dosage and filling vanadium cast iron in the ladle. Doping vanadium steel in the ladle is siliconindia, which is a byproduct of the production fartsy with siliconindia.

The method is as follows. Steel is smelted in the basic open-hearth furnaces with a capacity of 260 tons during the melt blending, consisting of 30% of steel scrap and 70% of liquid intermediate product, obtained by blowing liquid vanadium iron in a 22-ton converters and containing, in wt.%: a 3.2-3.7 carbon, 0.03 to 0.1 manganese, 0.03 to 0.1 silicon, 0.03 to 0.1 vanadium, 0.03 and 0.1 chromium, not more than 0.05 phosphorus, not more than 0.05 sulfur. The deoxidation and alloying of steel produced in the buckets by filing through a special bunker strictly metered portions of ferroalloys, providing a given chemical composition of the steel. One steel bucket (130 tons) consumption of ferroalloys is;

Silicomanganese - 1500 kg

Ferrosilicon - 1150 kg

Siliconindia - 1000 kg

To remove non-metallic inclusions and averaging steel chemical composition and temperature of the steel in the ladle is blown with nitrogen at a pressure of 2-6 bar and the General consumption of no more than 26 m3on the bucket. It does not increase the nitrogen content in the finished steel.

Chemical composition and mechanical properties of the steel are given in tables 1, 2. The test results of welded joints in table 3.

When testing connections resistance spot welding, the arc welded cruciform joints tack, softening almost was not.

Sources of information

1. GOST 5781-82. Hot-rolled steel for reinforcement of concrete structures. Technical conditions. - M.: Publishing house of standards, 1994.

2. GOST 380-88. Carbon steel of ordinary quality. Of the brand. - M.: Publishing house of standards, 1988.

3. USSR author's certificate N 336369, class C 22 C 38/12, BI N 14, 1972 (prototype).

4. RF patent N 2055094, class C 21 C 5/04, 7/06, BI N 6, 1996 (the prototype).

5. RF patent N 2044060, class C 21 C 5/04, 7/06, BI N 26, 1995.

1. Rebar hot rolled steel containing carbon, manganese, silicon, vanadium, chromium, Nickel, copper and iron, characterized in that it contains components in the following ratio, wt.%:

Carbon - 0,16-0,24

Manganese - 0.60 and 0.95 to

Silicon - 0,50-0,90

Vanadium - 0,12-0,20

Chromium - Not more than 0.20

Nickel is Not more than 0.15

Copper is Not more than 0.10

Iron - Rest

the ratio of temporary resistance to the yield strength is 1,25-1,40.

2. The method of steelmaking to obtain a hot rolled reinforcing steel, including the production of semi-natural-doped vanadium cast iron, steel production in steel-smelting unit, flow of molten steel in the ladle, RA is th scrap and liquid intermediate product, contains components in the following ratio, wt.%:

Carbon - 3,2-3,7

Manganese - 0,03-0,1

Silicon - 0,03-0,1

Vanadium - 0,03-0,1

Chrome - 0,03-0,1

Phosphorus - Not more than 0.05

Sulfur is Not more than 0.05

Iron - Rest

providing 14-58 wt.% vanadium in steel, and the remaining amount of vanadium is injected in the form of siliconindia in the bucket, the process of deoxidation and alloying of steel in the ladle carried out while purging with nitrogen.

3. The method according to p. 2, characterized in that the steel type siliconindia, which is a byproduct of the production of ferrovanadium.

 

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