KR20160065192A - A steel rebar and a production method thereof - Google Patents

Abstract

The present invention relates to a steel sheet comprising a steel sheet having a composition comprising 0.005 to 0.030% C, 0.3 to 0.6% Si, 1.2-2.5% Mn, 0.01% P, 0.01% S, 8.0-10.0% 3.0% of Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, and the balance of Fe and unavoidable impurities. The present invention also provides a method for producing a reinforcing bar. The reinforcing bars of the present invention are characterized by having excellent overall mechanical performance and corrosion resistance to satisfy seismic design requirements and at the same time improving the service life of reinforcing bars in seawater so that they can be widely used in reinforced concrete structures in marine environments .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to reinforcing bars,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforcing bar and a manufacturing method thereof in an alloy steel field.

As the maritime strategy consciousness of each country has been strengthened and modern marine science and technology has been developed, the construction of basic facilities such as land / marine bridge, harbor pier and offshore structures has entered the peak season. At the same time, the problem of durability of reinforcing steel, which is a main structural material, is becoming more important. The marine environment is a relatively harsh corrosion environment in the natural environment. Specified conditions of high temperature, high humidity, and high salt are very easy to cause steel corrosion, and reinforced concrete structures in Korea are generally subjected to severe corrosion phenomena after 10 to 15 years of use And it causes structure destruction, and the design life of 50 years can not be satisfied.

There are two methods to improve the corrosion resistance of concrete among concrete. Firstly, it is to apply an organic or inorganic coating layer to the carbon steel reinforcing bar. Secondly, steel reinforcing material having excellent corrosion resistance is obtained through alloying or other processing. In coated corrosion-resistant rebars, epoxy-coated rebars were the earliest research and development area has been widely used, but there are still intrinsic defects in epoxy-coated rebars, mainly due to the high brittleness of the coating layer, Defects in the coating layer cause corrosion centralization, serious partial corrosion occurs, and the bonding force with concrete is lowered compared with general reinforcing bars. In the US and European countries, stainless steel reinforcing bars have been developed and used to meet the design requirements of 100 years of use life of buildings. The critical concentration of corrosion is much higher than that of ordinary reinforcing bars, thus greatly improving the corrosion resistance of concrete structures. However, since the cost is huge and the manufacturing cost is 6 to 10 times that of ordinary reinforcing bars, it can not be used on a large scale during construction. Normally, it is used only in environments where core parts and conditions of buildings are poor. When stainless steel reinforcing bars are connected to ordinary reinforcing bars It can easily cause corrosion of macro cells and affects the service life of buildings.

The research and development of low-alloy corrosion resistant steel for non-reinforcing steel at home and abroad has been relatively mature. The US studied Mariner steel in the 50s of the 20th century and France developed APS20A steel in the 1960s. In the 70s, China also developed 10CrMoA1 seawater Released a corrosive steel. These steels have significantly improved corrosion resistance compared to normal carbon steels, but all of these steels can not be used in marine reinforced concrete structures because they still can not satisfy the relatively long service life required for reinforced concrete structures.

In the Chinese patent document CN102605255A, there is disclosed an alloy having an element content of 0.1 to 0.25% C, 0.5 to 0.90% Si, 0.7 to 1.5% Mn, 0.04 to 0.09% P, 0.015% Corrosion resistance of 400 MPa level of Cu, 0.1% to 0.4% of Ni, 0.1% or less of Cr, and 0.03% to 0.08% of V. The corrosion resistance of the steel is twice as high as that of ordinary steel, There is still a limit and it can not satisfy the life expectancy of 50 ~ 100 years of marine reinforced concrete buildings.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a steel reinforced concrete structure having excellent corrosion resistance and comprehensive mechanical performance, And a manufacturing method thereof.

In order to solve the above technical problem, the present invention is characterized in that the composition comprises 0.005 to 0.030% of C, 0.3 to 0.6% of Si, 1.2 to 2.5% of Mn, 0.01 or less of P, 0.01 or less of S, 10.0% Cr, 1.0-3.0% Mo, 0.2-0.4% Sn, 0.01-0.05% RE, and the balance Fe and unavoidable impurities.

The steel has a yield strength of 400 MPa and contains 0.005 to 0.030% of C, 0.3 to 0.6% of Si, 1.2 to 1.8% of Mn, 0.01 or less of P, 0.01 or less of S, 8.0 to 10.0 % Of Cr, 1.0 to 1.6% of Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, and the balance of Fe and unavoidable impurities.

The composition comprises 0.005 to 0.030% C, 0.3 to 0.6% Si, 1.2 to 2.5% Mn, 0.01% P, 0.01% S, 8.0-10.0% Cr, 1.0-3.0% Mo, 0.2 to 0.4% Sn, 0.01 to 0.05% RE, 0.04 to 0.18% V and / or 0.010 to 0.030% Ti, and the balance Fe and unavoidable impurities.

The steel has a yield strength of 500 MPa and contains 0.005 to 0.030% by weight of C, 0.3 to 0.6% of Si, 1.7 to 2.5% of Mn, 0.01 or less of P, 0.01 or less of S, % Of Cr, 1.5 to 2.0% of Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, 0.04 to 0.08% of V, and the balance of Fe and unavoidable impurities.

The steel has a yield strength of 600 MPa and contains 0.005-0.030% C, 0.3-0.6% Si, 1.7-2.5% Mn, 0.01% P, 0.01% S, 8.0-10.0 % Of Cr, 1.8 to 3.0% of Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, 0.10 to 0.18% of V, 0.01 to 0.030% of Ti and the balance of Fe and unavoidable impurities .

The microstructure of the reinforcing bars is ferrite and bainite, and the content of ferrite is 50% to 70%.

The ratio of the actual tensile strength to the actual yield strength of the reinforcing bars is greater than 1.25 and the total stress elongation percentage under the maximum load is greater than 9% , The after-fracture elongation percentage is greater than 18%, the corrosion rate by cyclic immersion corrosion test is less than 0.45 g / (m2h), the salt spray test corrosion rate is 0.45 g / (m2h) ).

The present invention also relates to a preliminary desulfurization treatment step (S1) for molten iron controlling the sulfur content to 0.01% or less;

A converter smelting step S2 in which molten iron, iron scrap and / or pig iron that has undergone the step (S1) process are put into a converter to smoothen the carbon content to less than 0.05% and the phosphorus content to less than 0.01%;

A step S3 for adding deoxidizing treatment to the Si and Mn alloying elements during the lecture progress and adding the carbon powder and the coarse material;

RH vacuum refining furnace. At the same time, oxygen is blown to remove C, the content of Cr and C elements is controlled within the required range, and the deoxidizing treatment is carried out using LF furnace, and then the alloy element Mn , Mo, Sn, RE and V and / or Ti, further adding calcium iron alloy, blowing an inert gas and flexibly stirring to control the content of each element within the required range, increasing the molten steel temperature, An outdoor refining step S4;

A continuous casting step (S5) of continuously casting molten steel into a continuous casting slab through a continuous casting machine under conditions to protect the casting; And

A rolling step of heating a continuous cast slab in a heating furnace to a temperature higher than the austenitizing temperature and then subjecting the precision rolled steel to rough cooling, intermediate rolling and precision rolling to obtain a reinforcing material of a necessary component S6). ≪ / RTI >

In the step (S2), the tapping temperature is 1690 占 폚 or less.

The temperature at which oxygen is blown and decarburized during the RH vacuum refining is 1605 DEG C or more in the step S4 and the temperature at which the deoxidizing treatment is carried out by refining in the LF furnace is 1575 DEG C or more, The oxygen content in the deoxidizing treatment is controlled to 0.002% to 0.005%, the soft stirring time is 5 minutes or more, and the molten steel temperature rises to 1570 to 1600 ° C.

Wherein the temperature is in the range of 950 to 960 占 폚 when the steel is heated on the cooling furnace at a temperature of 1100 to 1200 占 폚 in the heating furnace at the step S6 and the rolling start temperature before the rough rolling is 1030 to 1100 占 폚 And the precision rolling temperature is 950 to 1050 ° C.

C is an important strengthening element mainly in the form of carbide and acts to precipitate and refine the crystal grains. Since C has a strong affinity with Cr, C and Cr form a series of complex carbides And the generation of such carbides increases the strength and hardness of the steel and lowers the corrosion resistance of the steel. If the C content is too high, the plasticity and toughness of the steel decrease and the welding performance of the steel deteriorates.

Si is an important reducing agent and deoxidizer, and the addition of silicon to the steel component can significantly improve the elastic limit, yield point and tensile strength of the steel. Silicon is combined with molybdenum, tungsten, and chromium to improve corrosion resistance and antioxidation. However, if silicon content is increased, the welding performance of steel may be deteriorated.

Mn is a good deoxidizing agent and a dewaxing agent and has solid solution strengthening action to the steel and is an important tough strengthening element as well as an austenite forming element. When the manganese content is too high, the hardening property of steel is remarkably improved and the plasticity and weldability of steel are lowered. The effect of manganese on the corrosion resistance is not clear.

S and P are harmful impurity elements in the steelmaking process, and it is easy to form harmful foreign substances in the steel components, which reduces the toughness and plasticity of the steel. Although some of the durability steels are designed using Cu-P series components, there is a limit in improvement of corrosion resistance and phosphorus is easily concentrated on the grain boundary surface, so that the brittleness of the steel is increased. Therefore, in the present invention, the content of S and P is controlled to be extremely small Respectively, within a range of 0.01%.

Cr is an important element for improving antioxidant and corrosion resistance of steel, and improves the corrosion resistance of steel by promoting formation of a stable passivation film on the surface of steel under appropriate circumstances. However, the effect of chromium in the non-oxidizing medium is lower than that of molybdenum and nickel, and when the chromium element alone is added, the corrosion resistance of the seawater in the steel can not be significantly improved and the corrosion of the fitting is liable to occur.

Mo can universally improve the corrosion resistance of the steel and can passivate the surface of the steel in both the reducing acid and the strong oxidizing salt solution and prevent the steel from corrosion in the chloride solution. If the molybdenum content is high (> 3%), the antioxidant properties of the steel may deteriorate. Molybdenum in terms of the tissue performance promotes the miniaturization of the crystal grains and improves the hardenability and heat resistance of the steel.

Sn is a non-oxidizing metal which is not oxidized at ordinary temperature and air but is stable by forming a tin dioxide protective film on the surface in a high temperature environment. In addition, it is stable to water, slowly dissolves in diluted acid and can be quickly dissolved in agricultural products, and is mainly used for the production of alloys and tinned steel sheets. When added as an alloying element, it can be dissolved in the matrix, thereby increasing the electrode potential of the matrix, lowering the propelling power of the electrochemical corrosion of the steel itself, lowering the corrosion rate, and increasing the strength and hardness of the steel. Sn can interact with Cr and Mo elements to significantly improve the corrosion resistance of the steel.

Regarding RE, the addition of an appropriate amount of rare earth to a steel component can significantly improve the overall corrosion resistance of the steel, purify liquid steel and mixed deterioration, and improve the state of the interface between grain and grain boundaries. Improvement is an important material cause. The molten rare earth in the steel component is advantageous for improving the corrosion resistance of the steel matrix in order to increase the polarization resistance and the self-corrosion potential of the steel matrix.

The above-described technology of the present invention has the following advantages over the prior art.

(1) In the reinforcing bars of the present invention, the C content is controlled to 0.005 to 0.030%, the Si content is controlled to 0.3 to 0.6%, the Mn content is controlled to 1.2 to 2.5%, the S content and P content are controlled to 0.001% And a Cr element, a Mo element and a RE element in an amount of 8 to 10%, a Mo element in an amount of 1.0 to 3.0%, and an R element in an amount of 0.01 to 0.05% are added to a steel component and a Sn element in an amount of 0.2 to 0.4% The corrosion resistance of steel was improved by the combination of element composition ratio and interaction of Cr and Sn elements. The addition of Mo and RE elements improved the internal performance between corrosion resistance and corrosion of steel, And improved the service life of the rebar in seawater.

(2) In the reinforcing bars of the present invention, the component comprises 0.005 to 0.030% of C, 0.3 to 0.6% of Si, 1.2 to 1.8% of Mn, 0.01 or less of P, 0.01 or less of S, 8.0 to 10.0% of Cr 1.0 to 1.6% of Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, and the balance of Fe and unavoidable impurities. A reasonable component design yields corrosion resistant rebar with a yield strength of 400 MPa, which provides corrosion resistant seawater reinforcement that is inexpensive and can meet basic mechanical performance requirements.

(3) In the reinforcing bar of the present invention, the component is preferably composed of 0.005 to 0.030% of C, 0.3 to 0.6% of Si, 1.2 to 2.5% of Mn, 0.01 or less of P, 0.01 or less of S, 8.0 to 10.0% Cr, 1.0 to 3.0% of Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, 0.04 to 0.18% of V and / or 0.010 to 0.030% of Ti and the balance of Fe and unavoidable impurities. The microalloy element V and / or Ti content is further added to the steel component, V is a microalloy element, which can precipitate V (C, N) compound during the rolling process and inhibits austenite and ferrite growth, Strengthening, microcrystallization strengthening and constant solubility strengthening action, which significantly improves the strength of the steel, and thus lowers the carbon content to compensate for deficiencies in strength. Ti is an element for forming a strong carbonitride, and has grain refinement and precipitation strengthening action. At the same time, the carbon is preferentially bound to titanium to form a carbonitanium compound, so that chromium carbide precipitates in a steel containing chromium to avoid chromium deficiency at the grain boundary surface, thereby effectively preventing corrosion between grains. The microalloy elements V and / or Ti have excellent mechanical performance by reinforcing hardening, micro-grain strengthening and precipitation strengthening during VCN and / or TiCN generation, thereby improving the strength of the steel.

(4) In the reinforcing bars of the present invention, by controlling the element content in the steel component, particularly the microalloy element V and / or the Ti content, steel having various strength requirements is produced. For example, in a steel having a yield strength of 500 MPa, the steel may contain 0.005 to 0.030% of C, 0.3 to 0.6% of Si, 1.7 to 2.5% of Mn, 0.01 or less of P, 0.01 or less of S, Cr, 1.5 to 2.0% of Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, 0.04 to 0.08 of V, and the balance of Fe and unavoidable impurities, or a steel having a yield strength of 600 MPa Wherein the composition comprises 0.005 to 0.030% of C, 0.3 to 0.6% of Si, 1.7 to 2.5% of Mn, 0.01 or less of P, 0.01 or less of S, 8.0 to 10.0% of Cr, 1.8 to 3.0% of Mo, 0.2 To 0.4% of Sn, 0.01 to 0.05% of RE, 0.10 to 0.18% of V, 0.01 to 0.030% of Ti, and the balance of Fe and unavoidable impurities.

(5) In the reinforcing bars of the present invention, the ferrite ratio is 50 to 70%, the bainite structure has good toughness, and ferrite has a good overall dynamic performance by controlling rationally the excellent aspect ratio , An elongation of greater than 18% on the basis of the required yield strength and tensile strength, a ratio of actual tensile strength to actual yield strength of greater than 1.25, a total elongation of greater than 9% under maximum load, .

(6) In the method of manufacturing a reinforcing bar of the present invention, the content of S is controlled through the KR degassing process, the content of P in the converter is controlled, and the Si and Mn alloying elements are added during the ladle work process, Carbon powder and additives are added to form a reducing atmosphere in the refining furnace. Oxygen is blown into the RH vacuum refining furnace to decarburize, thereby controlling the content of carbon and chromium, conducting the deoxidizing treatment in the LF furnace, By adding the remaining alloying elements, it is possible to control the content of oxygen and various alloying elements, further modify the foreign matter by adding calcium-iron alloy, make the components uniform through flexible agitation, remove foreign matter, Thereby controlling the gas content in the steel and preventing oxidation and secondary entrainment of foreign matter, and heating the cast slab prior to rolling in the furnace from 1100 to 1200 ° C It is possible to strictly control the amount of deformation of the steel during rolling by performing rough rolling, intermediate rolling, and precision rolling at the time of rolling so that the elements of the steel are completely austenitized and the steel is fully austenitized. So that the precipitation strengthening action of the alloying elements VCN and / or TiCN can be sufficiently exhibited. After the rolling, the steel is placed in a cooling bed to cool the air so that the final microstructure of the steel becomes ferrite with bainite.

(7) In the method of manufacturing a reinforcing bar of the present invention, it is possible to reduce the oxygen content in the steel component, improve the element yield, reduce foreign matter in the steel component, improve the converter life, And reduced the manufacturing costs of steel.

(8) In the method for producing a reinforcing bar of the present invention, by controlling the temperature at which oxygen is blown and decarburized at 1605 DEG C or more during RH vacuum refining, the decarburization effect on RH can be enhanced and the content of carbon and chromium elements in the steel component can be controlled It is advantageous. In the LF furnace, it is advantageous to control the refining deoxidizing temperature to 1575 ° C or higher, to increase the refining deoxidizing effect to LF, and to control the oxygen content within a limited range. By controlling the oxygen content in the deoxidizing treatment in the LF furnace from 0.002% to 0.005%, foreign substances in the steel components are effectively controlled to improve the steel quality. The flexible agitation time is controlled to 5 minutes or more to make the steel component and temperature more uniform, and it is advantageous to remove the floating of the foreign matter. By increasing the temperature of the molten steel to 1570 to 1600 DEG C before continuous casting, the continuous casting operation proceeds smoothly.

(9) In the method of manufacturing a reinforcing bar of the present invention, the steel is heated to a temperature not lower than the austenitizing temperature by controlling the casting slab to be heated at 1100 to 1200 캜 in a heating furnace to set the alloying element in the steel component to a solid state. The rolling starting temperature is controlled to 1030 to 1100 占 폚, the temperature during precision rolling is controlled to 950 to 1050 占 폚, and the strengthened phase is precipitated by inducing deformation to increase the strength of the steel. By controlling the temperature at which the steel material is placed in the cooling bed, the required microstructure is ferrite and bainite.

The composition comprises 0.005 to 0.030% C, 0.3 to 0.6% Si, 1.2 to 2.5% Mn, 0.01% P, 0.01% S, 8.0-10.0% Cr, 1.0-3.0% Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, and the balance of Fe and unavoidable impurities.

In the method of manufacturing a reinforcing bar of the present invention, the quantity of harmful elements and foreign substances in the steel component is greatly reduced, and the steel quality, mechanical performance and corrosion resistance are improved by accurately controlling the element content and temperature of the liquid steel in each step.

The reinforcing bars produced by the reinforcing bar manufacturing method of the present invention allow the microstructure of the steel to be ferrite and bainite through reasonable processing steps. The ratio of ferrite to ferrite is 50 to 70%, the bainite structure has good toughness, and ferrite has a good overall tensile strength by controlling ratios of excellent plasticity and excellent yield strength, The elongation ratio is greater than 18% on the basis of the tensile strength, the ratio of the actual tensile strength to the actual yield strength is greater than 1.25, the total elongation under the maximum load is greater than 9%, and the steel component has a good seismic performance.

In order to more easily and accurately understand the contents of the present invention, the present invention will be described in detail based on concrete examples and drawings of the present invention. among them,
1 is a microstructure view of a reinforcing bar according to the present invention.

The rebar component in Examples 1-10 and the rebar component (wt.%) In Comparative Example 1-3 C Si Mn Cr Mo RE Sn V Ti P S Example 1 0.005 0.60 2.5 9.0 1.0 0.05 0.20 - - <0.01 <0.01 Example 2 0.030 0.45 1.2 10.0 3.0 0.01 0.40 - - <0.01 <0.01 Example 3 0.015 0.30 1.8 8.0 1.6 0.03 0.30 - - <0.01 <0.01 Example 4 0.020 0.5 2.3 8.5 2.2 0.02 0.25 0.04 - <0.01 <0.01 Example 5 0.025 0.55 1.7 8.2 2.3 0.02 0.35 0.18 0.01 <0.01 <0.01 Example 6 0.009 0.35 1.8 8.5 2.5 0.04 0.36 0.1 0.03 <0.01 <0.01 Example 7 0.012 0.40 2.2 9.5 1.5 0.03 0.28 - 0.02 <0.01 <0.01 Example 8 0.012 0.57 1.8 9.7 2.0 0.03 0.21 0.08 - <0.01 <0.01 Example 9 0.018 0.50 1.9 9.0 1.7 0.02 0.30 0.06 - <0.01 <0.01 Example 10 0.026 0.50 2.3 8.1 1.8 0.05 0.40 0.15 0.02 <0.01 <0.01 Comparative Example 1 0.23 0.54 1.5 - - - - - - <0.01 <0.01 Comparative Example 2 0.015 0.48 1.9 9.1 1.8 0.02 0.60 - - <0.01 <0.01 Comparative Example 3 0.024 0.52 2.0 9.8 2.0 0.02 - - - <0.01 <0.01

[Example 1]

This embodiment provides reinforcing bars composed of C, Si, Mn, P, S, Cr, Mo, Sn, RE, Fe and unavoidable impurities, wherein the weight percentage of each component is as shown in Table 1, The performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, so that the sulfur content in the steel component is controlled to 0.01% or less A preliminary desulfurization treatment step (S1);

The molten iron and iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt less than 0.01% of the phosphorus content less than 0.05%, and the ladle is top and bottom a combined smelting step S2, which is a combined blown converter;

The lubrication temperature is 1680 ℃ and the Si, Mn alloying element is added to the lubrication process, the deoxidizing process is performed, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

RH vacuum refining furnace. At the same time, oxygen was blown at 1605 ℃ to remove C, decarburized to remove C element, and Cr and C element contents were controlled within the required range. The deoxidizing treatment is performed so that the oxygen content in the liquid steel becomes 40 ppm, and the alloying elements Mn, Mo, Sn and RE necessary for the steel component are added after the deoxidizing treatment. The alloying element material to be added may be a pure metal element In general, it is added in the form of an iron alloy, and a calcium-iron alloy is further added to denature the foreign substance. Then, an inert gas is blown into the mixture and the mixture is stirred. The stirring time is 5 min. And the content of each element was controlled to fall within the range shown in Table 1 in Table 1. In the latter stage of treatment with LF, the molten steel temperature was raised to 1580 DEG C I, the temperature is rooe polishing step (S4) is intended to continuously cast it be to proceed freely, in addition of the coating agent, the coating agent is carbonized rice hull generally;

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous cast slabs were heated to 1100 DEG C in a heating furnace, and subjected to rough rolling, intermediate rolling and precision rolling using a rod and wire rolling machine. The rolling starting temperature was 1030 DEG C and the precision rolling temperature Is 950 占 폚 and the precision rolled steel material is placed on the cooling bed without cooling the water after the precision rolling and the air is cooled to room temperature to obtain the reinforcing material shown in Table 1. The cooling phase temperature is 900 占 폚, And a rolling step (S6) of finally obtaining a bainite and a ferrite microstructure through a control process.

[Example 2]

This embodiment provides reinforcing bars composed of C, Si, Mn, P, S, Cr, Mo, Sn, RE, Fe and unavoidable impurities, wherein the weight percentage of each component is as shown in Table 1, The performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, so that the sulfur content in the steel component is controlled to 0.01% or less A preliminary desulfurization treatment step (S1);

The molten iron and iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt less than 0.01% of the phosphorus content less than 0.05%, and the ladle is top and bottom a combined smelting step S2, which is a combined blown converter;

The liquefaction temperature is 1690 ℃ and the Si, Mn alloying element is added to the liquefaction process, the deoxidizing process is carried out, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

In addition, Cr element was added to the RH vacuum refining furnace and oxygen was blown at 1625 ° C to remove C, to remove C element through decarburization process, to control the Cr and C element content within the required range, The deoxidizing treatment is performed so that the oxygen content in the liquid steel becomes 20 ppm and the alloying elements Mn, Mo, Sn and RE necessary for the steel component are added after the deoxidizing treatment. The alloy element material to be added may be a pure metal element In general, it is added in the form of an iron alloy, and calcium-iron alloy is further added to denature the foreign substance, and then an inert gas is blown thereinto and the mixture is stirred. The flexible stirring time is 6 min. And the content of each element was controlled to fall within the range shown in Table 2 in Table 1. In the latter stage of treatment with LF, the molten steel temperature was raised to 1600 ° C Sikineunde, the temperature is rooe polishing step (S4) is intended to continuously cast it be to proceed freely, in addition of the coating agent, the coating agent is carbonized rice hull generally;

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous cast slab was heated to 1200 DEG C in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling using a rod and wire rolling machine. The rolling starting temperature was 1100 DEG C and the precision rolling temperature Is 1050 占 폚 and the precision rolled steel material is placed on the cooling bed without cooling the water after the precision rolling and the air is cooled to room temperature to obtain the reinforcing material shown in Table 1. The cooling phase temperature is 960 占 폚, And a rolling step (S6) of obtaining a microstructure structure of bainite and ferrite finally through a control process.

[Example 3]

This embodiment provides reinforcing bars composed of C, Si, Mn, P, S, Cr, Mo, Sn, RE, Fe and unavoidable impurities, wherein the weight percentage of each component is as shown in Table 1, The performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, so that the sulfur content in the steel component is controlled to 0.01% or less A preliminary desulfurization treatment step (S1);

The molten steel, iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt and lyse the content of less than 0.05% in a content of less than 0.01%, and the converter is fed to the converter smelting step (S2);

The liquefaction temperature is 1685 ℃ and the Si, Mn alloying element is added to the ladle, the deoxidizing process is carried out, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

RH vacuum refining furnace. At the same time, oxygen was blown at 1610 ℃ to remove C, decarburized to remove C element, and Cr and C element contents were controlled within the required range. The deoxidizing treatment is performed so that the oxygen content in the liquid steel becomes 30 ppm and the alloying elements Mn, Mo, Sn and RE necessary for the steel component are added after the deoxidizing treatment. The alloying element material to be added may be a pure metal element In general, it is added in the form of an iron alloy, and calcium-iron alloy is further added to denature the foreign substance, and then an inert gas is blown thereinto and the mixture is stirred. The flexible stirring time is 6 min. And the content of each element was controlled to fall within the range shown in Table 3 in Table 1. In the latter stage of treatment with LF, the molten steel temperature was increased to 1570 DEG C Sikineunde, the temperature is rooe polishing step (S4) is intended to continuously cast it be to proceed freely, in addition of the coating agent, the coating agent is carbonized rice hull generally;

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous casting slab was heated to 1120 DEG C in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling using a continuous bar steel wire rolling mill. The rolling starting temperature was 1050 DEG C, the precision rolling temperature was 960 DEG C, Thereafter, the steel material as shown in Table 1 is obtained by placing the precision rolled steel material on a cooling bed and air-cooling to room temperature after the water cooling is not performed. The cooling material phase temperature is 910 DEG C, And a rolling step (S6) for obtaining a ferrite microstructure and a knit structure.

[Example 4]

The present embodiment provides reinforcing bars composed of C, Si, Mn, P, S, Cr, Mo, Sn, RE, V, Fe and unavoidable impurities, wherein the weight percentage of each component is as shown in Table 1 , The mechanical performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, so that the sulfur content in the steel component is controlled to 0.01% or less A preliminary desulfurization treatment step (S1);

The molten steel, iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt and lyse the content of less than 0.05% in a content of less than 0.01%, and the converter is fed to the converter smelting step (S2);

The liquefaction temperature is 1690 ℃ and the Si, Mn alloying element is added to the liquefaction process, the deoxidizing process is carried out, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

RH vacuum refining furnace. At the same time, oxygen is blown at 1620 ° C to remove C, decarburize, remove C element, control the Cr and C element contents to within the required range, and use LF furnace at 1590 ° C Mo, Sn, RE and V are added to the steel component after the deoxidizing treatment. The alloying element material to be added is a pure metal element However, in general, it is added in the form of an iron alloy. Further, a calcium-iron alloy is added to modify the foreign substance, then an inert gas is blown into the mixture and the mixture is stirred. The flexible stirring time is 6 min. And the content of each element was controlled within the range shown in Table 4 in Table 1. In the latter stage of treatment with LF, the molten steel temperature was controlled to 1585 DEG C Sikineunde w, the temperature is rooe polishing step (S4) is intended to continuously cast it be to proceed freely, in addition of the coating agent, the coating agent is carbonized rice hull generally;

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous casting slab was heated to 1180 캜 in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling using a continuous bar steel wire rolling mill. The rolling starting temperature was 1040 캜, the precision rolling temperature was 990 캜, The steel material as shown in Table 1 is obtained by placing the precision rolled steel material on the cooling bed and then air cooling to room temperature so that the cooling phase temperature is 950 DEG C and the final cooling rate is controlled through the rolling control and cooling control process, And a rolling step (S6) for obtaining a ferrite microstructure and a knit structure.

[Example 5]

This embodiment provides reinforcing bars composed of C, Si, Mn, P, S, Cr, Mo, Sn, RE, V, Ti, Fe and unavoidable impurities, And the mechanical performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, so that the sulfur content in the steel component is controlled to 0.01% or less A preliminary desulfurization treatment step (S1);

The molten steel, iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt and lyse the content of less than 0.05% in a content of less than 0.01%, and the converter is fed to the converter smelting step (S2);

The lubrication temperature is 1675 ℃ and the Si, Mn alloying element is added to the lubrication process, the deoxidizing process is performed, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

RH vacuum furnace. At the same time, oxygen is blown at 1615 ° C to remove C, decarburize, remove C element, control the Cr and C element contents to within the required range, and use LF furnace at 1580 ° C Mo, Sn, RE, V and Ti are added to the steel component after the deoxidizing treatment. The alloying element material to be added is pure metal However, in general, it is added in the form of an iron alloy. In addition, a calcium-iron alloy is added to modify the foreign substance, then an inert gas is blown into the mixture and the mixture is stirred. The flexible stirring time is 7 min. The content of each element was controlled to fall within the range shown in Table 5 in Table 1. In the latter stage of treatment with LF, the molten steel temperature was controlled at 1580 ° C To raise, the temperature is rooe polishing step (S4) is intended to continuously cast it be to proceed freely, in addition of the coating agent, the coating agent is carbonized rice hull generally;

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous casting slab was heated to 1190 占 폚 in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling using a continuous bar steel wire rolling mill. The rolling start temperature was 1095 占 폚, the precision rolling temperature was 1030 占 폚, The steel material as shown in Table 1 is obtained by placing the precision rolled steel material on the cooling bed and then air cooling to room temperature so that the cooling phase temperature is 950 DEG C and the final cooling rate is controlled through the rolling control and cooling control process, And a rolling step (S6) for obtaining a ferrite microstructure and a knit structure.

[Example 6]

This embodiment provides reinforcing bars composed of C, Si, Mn, P, S, Cr, Mo, Sn, RE, V, Ti, Fe and unavoidable impurities, And the mechanical performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, thereby controlling the sulfur content in the steel component to 0.01% or less. A preliminary desulfurization treatment step (S1);

The molten steel, iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt and lyse the content of less than 0.05% in a content of less than 0.01%, and the converter is fed to the converter smelting step (S2);

The liquefaction temperature is 1670 ℃ and the Si, Mn alloying element is added to the liquefaction process, the deoxidizing process is performed, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

RH vacuum refining furnace. At the same time, oxygen is blown at 1610 ℃ to remove C, decarburize, remove C element, control Cr and C element content within the required range, and use LF furnace at 1580 ℃ Mo, Sn, RE, V and Ti are added to the steel component after the deoxidizing treatment. The alloying element material to be added is pure metal However, in general, it is added in the form of an iron alloy. In addition, a calcium-iron alloy is added to modify the foreign substance, then an inert gas is blown into the mixture and the mixture is stirred. The flexible stirring time is 7 min. The content of each element was controlled to fall within the range shown in Table 6 in Table 1. In the latter stage of treatment with LF, the molten steel temperature was controlled to 1590 ° C To raise, the temperature is rooe polishing step (S4) is intended to continuously cast it be to proceed freely, in addition of the coating agent, the coating agent is carbonized rice hull generally;

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous casting slab was heated to 1185 DEG C in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling using a continuous bar steel wire rolling mill. The rolling start temperature was 1085 DEG C, the precision rolling temperature was 1035 DEG C, Thereafter, the steel material as shown in Table 1 is obtained by placing the precision rolled steel material on a cooling bed and air-cooling to room temperature after the water cooling is not performed. The cooling material temperature is 955 DEG C, And a rolling step (S6) for obtaining a ferrite microstructure and a knit structure.

[Example 7]

This embodiment provides reinforcing bars made of C, Si, Mn, P, S, Cr, Mo, Sn, RE, Ti, Fe and unavoidable impurities, wherein the weight percentage of each component is as shown in Table 1 , The mechanical performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, so that the sulfur content in the steel component is controlled to 0.01% or less A preliminary desulfurization treatment step (S1);

The molten steel, iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt and lyse the content of less than 0.05% in a content of less than 0.01%, and the converter is fed to the converter smelting step (S2);

The liquefaction temperature is 1685 ℃ and the Si, Mn alloying element is added to the ladle, the deoxidizing process is carried out, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

RH vacuum furnace. At the same time, oxygen is blown at 1615 ° C to remove C, decarburize, remove C element, control the Cr and C element contents to within the required range, and use LF furnace at 1580 ° C Mo, Sn, RE and Ti are added to the steel component after the deoxidizing treatment. The alloying element material to be added is pure metal element However, in general, it is added in the form of an iron alloy. Further, a calcium-iron alloy is added to modify the foreign substance, then an inert gas is blown into the mixture and the mixture is flexibly stirred. The flexible stirring time is 7 min. And the content of each element was controlled within the range shown in Table 7 in Table 1. In the latter stage of treatment with LF, the molten steel temperature was controlled to 1585 DEG C The temperature is intended to allow the continuous casting to progress smoothly, and the cladding is added, the cladding is generally an out-of-furnace smelting step (S4);

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous casting slab was heated to 1180 캜 in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling using a continuous bar steel wire rolling mill. The rolling starting temperature was 1080 캜, the precision rolling temperature was 1020 캜, The steel material as shown in Table 1 is obtained by placing the precision rolled steel material on a cooling bed and then cooling it to room temperature so that the cooling phase temperature is 940 DEG C and the final cooling is performed through the rolling control and cooling control process, And a rolling step (S6) for obtaining a ferrite microstructure and a knit structure.

[Example 8]

The present embodiment provides reinforcing bars composed of C, Si, Mn, P, S, Cr, Mo, Sn, RE, V, Fe and unavoidable impurities, wherein the weight percentage of each component is as shown in Table 1 , The mechanical performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, so that the sulfur content in the steel component is controlled to 0.01% or less A preliminary desulfurization treatment step (S1);

The molten steel, iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt and lyse the content of less than 0.05% in a content of less than 0.01%, and the converter is fed to the converter smelting step (S2);

The lubrication temperature is 1680 ℃ and the Si, Mn alloying element is added to the lubrication process, the deoxidizing process is performed, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

RH vacuum refining furnace. At the same time, oxygen was blown at 1610 ℃ to remove C, decarburized to remove C element, and Cr and C element contents were controlled within the required range. Mo, Sn, RE and V are added to the steel component after the deoxidizing treatment. The alloying element material to be added is a pure metal element However, in general, it is added in the form of an iron alloy. Further, a calcium-iron alloy is added to modify the foreign substance, then an inert gas is blown into the mixture and the mixture is flexibly stirred. The flexible stirring time is 7 min. And the content of each element was controlled to fall within the range shown in Example 8 in Table 1. In the latter stage of treatment with LF, the molten steel temperature was controlled to 1590 占 폚 Sikineunde w, the temperature is rooe polishing step (S4) is intended to continuously cast it be to proceed freely, in addition of the coating agent, the coating agent is carbonized rice hull generally;

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous casting slab was heated to 1150 占 폚 in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling using a continuous bar steel wire rolling mill. The rolling starting temperature was 1065 占 폚, the precision rolling temperature was 1025 占 폚, The steel material as shown in Table 1 is obtained by placing the precision rolled steel material on the cooling bed without air cooling and then cooling the air to room temperature. The cooling material temperature is 965 DEG C, And a rolling step (S6) for obtaining a ferrite microstructure and a knit structure.

[Example 9]

This embodiment provides reinforcing bars composed of C, Si, Mn, P, S, Cr, Mo, Sn, RE, V, Ti, Fe and unavoidable impurities, And the mechanical performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, so that the sulfur content in the steel component is controlled to 0.01% or less A preliminary desulfurization treatment step (S1);

The molten steel, iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt and lyse the content of less than 0.05% in a content of less than 0.01%, and the converter is fed to the converter smelting step (S2);

The lubrication temperature is 1675 ℃ and the Si, Mn alloying element is added to the lubrication process, the deoxidizing process is performed, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

RH vacuum refining furnace. At the same time, oxygen was blown at 1605 ℃ to remove C, decarburized to remove C element, and Cr and C element contents were controlled within the required range. Mo, Sn, RE and V are added to the steel component after the deoxidizing treatment. The alloying element material to be added is a pure metal element However, in general, it is added in the form of an iron alloy. Further, a calcium-iron alloy is added to modify the foreign substance, then an inert gas is blown into the mixture and the mixture is flexibly stirred. The flexible stirring time is 7 min. And the content of each element was controlled to fall within the range shown in Example 9 in Table 1. In the latter stage of treatment with LF, the molten steel temperature was controlled to 1580 占 폚 Sikineunde w, the temperature is rooe polishing step (S4) is intended to continuously cast it be to proceed freely, in addition of the coating agent, the coating agent is carbonized rice hull generally;

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous casting slab was heated to 1105 DEG C in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling using a continuous bar steel wire rolling mill. The rolling starting temperature was 1045 DEG C, the precision rolling temperature was 1005 DEG C, Thereafter, the steel material as shown in Table 1 is obtained by placing the precision rolled steel material on a cooling bed and cooling the steel material to room temperature. The temperature of the cooling material phase is 945 占 폚, and finally, through the rolling control and cooling control process, And a rolling step (S6) for obtaining a ferrite microstructure and a knit structure.

[Example 10]

This embodiment provides reinforcing bars composed of C, Si, Mn, P, S, Cr, Mo, Sn, RE, V, Ti, Fe and unavoidable impurities, And the mechanical performance is as shown in Table 2, and the corrosion resistance performance is as shown in Table 3.

In this embodiment, the sulfur content is controlled to be 0.01% or less, and the sulfur element is an impurity element, which may deteriorate the mechanical performance and corrosion resistance of the steel component. Generally, since the sulfur element can not be removed from the converter, In order to reduce the sulfur content, the preliminary desulfurization treatment is performed on the steel in the molten iron. In order to increase the desulfurization efficiency, the blast furnace slag must be removed before the desulfurization. The desulfurizing agent is mixed with the lime powder and fluorite mixed at a mass ratio of 9: Sulfurization slag is removed after the desulfurization-treated molten iron is stopped, so that the desulfurization slag is prevented from entering the converter and the sulfur element is prevented from flowing into the converter, so that the sulfur content in the steel component is controlled to 0.01% or less A preliminary desulfurization treatment step (S1);

The molten steel, iron scrap and / or pig iron that have undergone the step (S1) treatment are added to the converter to smelt and lyse the content of less than 0.05% in a content of less than 0.01%, and the converter is fed to the converter smelting step (S2);

The liquefaction temperature is 1685 ℃ and the Si, Mn alloying element is added to the ladle, the deoxidizing process is carried out, the carbon powder and the coagulant are added, the protective gas is blown in the lubrication process, The Si and Mn alloy elements added by using the fluidity of the liquid steel are more thoroughly deoxidized and the foreign matters are suspended and removed. The carbon powder and the coagulant are added to increase the carbon content in the steel, and the reduction slag A preparing step (S3) of preparing for a subsequent furnace refining step by manufacturing the furnace;

In addition, Cr element was added to the RH vacuum refining furnace and oxygen was blown at 1620 ° C to remove C, to remove C element through decarburization process, to control the Cr and C element content within the required range, Mo, Sn, RE, V and Ti are added to the steel component after the deoxidizing treatment. The alloying element material to be added is pure metal However, in general, it is added in the form of an iron alloy. In addition, a calcium-iron alloy is added to modify the foreign substance, then an inert gas is blown into the mixture and the mixture is stirred. The flexible stirring time is 7 min. The content of each element is controlled to fall within the range shown in Table 10, and the molten steel temperature is controlled to 1595 DEG C To raise, the temperature is rooe polishing step (S4) is intended to continuously cast it be to proceed freely, in addition of the coating agent, the coating agent is carbonized rice hull generally;

A continuous casting step (S5) of continuously casting molten steel into a small square slab of 150 mm x 150 mm through a continuous casting machine under conditions to protect the casting; And

The continuous cast slab was heated to 1195 DEG C in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling using a continuous bar steel wire rolling mill. The rolling starting temperature was 1095 DEG C, the precision rolling temperature was 1045 DEG C, Thereafter, the steel material as shown in Table 1 is obtained by placing the precision rolled steel material on a cooling bed and air-cooling to room temperature after the water cooling is not performed. The cooling material temperature is 955 DEG C, And a rolling step (S6) of obtaining a ferrite microstructure and a nitrite structure.

Experimental Example

In order to demonstrate the effects of the present invention, the reinforcing bars prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were tested and the following experiment was conducted.

1. Experimental Method

1.1 Mechanical performance test: Proceeding with reference to "GB 1499.2-2007 Reinforced Concrete Steel Part 2: Hot Rolled Steel". The yield strength (R0.2), tensile strength (Rm) and elongation (A) of the steel bars were measured.

1.2 Corrosion resistance test

1.2.1 Periodic Infiltration Corrosion Experiment: In May 2012, the Chinese Iron and Steel Industry Association submitted a proposal from the Steel Research Institute and the Metallurgical Industry Information Standardization Research Unit, "A Comment on the Test Method for Corrosion of Reinforcement in Chloride Ion Environment" .

The sample is a cylinder of 13 mm x 50 mm,

The experimental solution is a sodium chloride solution in which the initial concentration is (0.34 ± 0.009) mol? L-1 (mass fraction is 2.0% ± 0.05%). Specific experimental conditions are as follows.

Temperature: 45 ° C ± 2 ° C

Humidity: 70% ± 10% RH

Solution PH value: 6.5-7.2

Experiment time: 360h

Each cycle: 60 min ± 5 min, infiltration time: 12 min ± 2 min

Maximum sample surface temperature after baking: 70 ° C ± 10 ° C

1.2.2 Salt Spray Corrosion Experiment: Proceeding with reference to "GBT10125-1997, artificial atmosphere corrosion test, salt water spray test".

The sample is a sample of 3 mm x 15 mm x 40 mm,

The experimental solution is a sodium chloride solution of (50 ± 5) g? L-1 (5.0% ± 0.5% mass fraction). Specific experimental conditions are as follows.

Temperature: 35 ° C ± 2 ° C

Solution PH value: 6.5-7.2

Experiment time: 360h

2. Experimental results

Table 2 shows the mechanical performance effects of Examples 1 to 10 and Comparative Examples 1 to 3, and Table 3 shows the corrosion resistance performance effects of Examples 1 to 10 and Comparative Examples 1 to 3.

Mechanical performance effect R _0.2 / MPa R _m / MPa A /% R _m / R _0.2 A _gt / Example 1 432 627 24.5 1.45 11.8 Example 2 408 613 25.3 1.50 12.6 Example 3 482 696 24.5 1.44 11.1 Example 4 561 728 18.9 1.30 10.8 Example 5 611 793 19.6 1.29 10.5 Example 6 554 755 20.8 1.36 10.3 Example 7 524 716 21.2 1.37 10.7 Example 8 523 743 25.0 1.42 11.3 Example 9 536 729 21.0 1.36 10.7 Example 10 621 795 18.0 1.28 9.5 Comparative Example 1 435 632 22.0 1.45 12.0 Comparative Example 2 486 586 13.4 1.21 6.2 Comparative Example 3 477 687 24.8 1.44 11.0

Corrosion performance effect Periodic invasion corrosion experiment Salt water spray experiment Corrosion
(g / m ² · h) Relative corrosion Improved corrosion resistance
(%) Corrosion
(g / m ² · h) Relative corrosion Improved corrosion resistance
(%) Example 1 0.415 0.127 690 0.411 0.130 666 Example 2 0.191 0.058 1616 0.205 0.065 1437 Example 3 0.419 0.128 682 0.432 0.137 629 Example 4 0.356 0.109 821 0.367 0.117 758 Example 5 0.441 0.135 643 0.445 0.141 608 Example 6 0.349 0.106 839 0.360 0.114 775 Example 7 0.386 0.118 749 0.395 0.125 697 Example 8 0.272 0.083 1105 0.288 0.091 994 Example 9 0.370 0.113 786 0.381 0.121 727 Example 10 0.433 0.132 657 0.435 0.138 624 Comparative Example 1 3.278 One - 3.150 One - Comparative Example 2 0.365 0.111 798 0.377 0.120 736 Comparative Example 3 0.456 0.151 561 0.463 0.160 526

(All of the relative corrosion degrees in Table 3 refer to Comparative Example 1, and the relative corrosion degree of Comparative Example 1 was set to 1.)

3, the corrosion resistance of the reinforcing bars was improved by adding Cr, Sn, Mo, and RE elements in Examples 1 to 10, and the corrosion resistance was improved by 600% or more as compared with Comparative Example 1. As can be seen from the corrosion resistance performance of the comparative example 3, the reinforcing bars containing no Sn element under the condition of the same other element content do not have a significant improvement in the corrosion resistance performance as compared with the reinforcing bars containing the Sn element. Compared with Examples 1, 2 and 3 and Comparative Example 2, when the Sn content is 0.02 to 0.04%, the corrosion resistance of the reinforcing bars is improved as the Sn content is increased, but the yield strength and tensile strength are lowered and the Sn content is 0.04% , The corrosion resistance of the reinforcing bars is not significantly improved but adversely affects the mechanical performance. In particular, the elongation of the reinforcing bars and the total elongation under the maximum load are significantly lowered, and the ratio of the actual tensile strength to the actual yield strength is greatly reduced do. Examples 4 to 10 are reinforcing bars to which V and / or Ti elements are added. As can be seen from Table 2, when the V and / or Ti elements are added, the yield strength and tensile strength of the reinforcing bars are improved, , The ratio of the actual tensile strength to the actual yield strength is greater than 1.25, the total elongation at the maximum load is greater than 9%, and the steel has good seismic performance.

The reinforcing bars of the present invention can precisely control elemental components and temperature during the smelting process through a rational component design, and combine the rolling control and the cooling control process to form bainite and ferrite (content ratio of ferrite: 50% to 70% As shown in FIG. 1, since the reinforcing bars have excellent mechanical and corrosion resistance, and the corrosion resistance is improved by 6 times or more as compared with the ordinary reinforcing bars, it can satisfy the service life requirement of the reinforced concrete structure during the marine process.

As can be seen from the above, the embodiment is an example for clarifying the present invention and is not intended to limit the embodiment. Those skilled in the art will be able to make other variations or modifications based on the above description. It is not necessary to exemplify all embodiments herein, but obvious changes or variations based on them are still within the scope of protection of the present invention.

Claims (13)

The composition comprises 0.005 to 0.030% C, 0.3 to 0.6% Si, 1.2 to 2.5% Mn, 0.01% P, 0.01% S, 8.0-10.0% Cr, 1.0-3.0% Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, and the balance of Fe and unavoidable impurities.
The method according to claim 1,
Wherein the composition comprises 0.005 to 0.030% C, 0.3-0.6% Si, 1.2-1.8% Mn, 0.01% P, 0.01% S, 8.0-10.0% Cr, 1.0-1.6% Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, and the balance of Fe and unavoidable impurities.
The composition comprises 0.005 to 0.030% C, 0.3 to 0.6% Si, 1.2 to 2.5% Mn, 0.01% P, 0.01% S, 8.0-10.0% Cr, 1.0-3.0% Mo, 0.2 to 0.4% Sn, 0.01 to 0.05% RE, 0.04 to 0.18% V and / or 0.010 to 0.030% Ti, the balance being Fe and unavoidable impurities.
The method of claim 3,
Wherein the composition comprises 0.005 to 0.030% C, 0.3 to 0.6% Si, 1.7 to 2.5% Mn, 0.01% P, 0.01% S, 8.0-10.0% Cr, 1.5-2.0% Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, 0.04 to 0.08% of V, and the balance of Fe and unavoidable impurities.
The method of claim 3,
Wherein the composition comprises 0.005-0.030% C, 0.3-0.6% Si, 1.7-2.5% Mn, 0.01% P, 0.01% S, 8.0-10.0% Cr, 1.8-3.0% Mo, 0.2 to 0.4% of Sn, 0.01 to 0.05% of RE, 0.10 to 0.18% of V, 0.01 to 0.030% of Ti, and the balance of Fe and unavoidable impurities.
6. The method according to any one of claims 1 to 5,
Wherein the microstructure of the reinforcing bars is ferrite and bainite, and the content of ferrite in the reinforcing bars is 50% to 70%.
7. The method according to any one of claims 1 to 6,
Wherein the ratio of the actual tensile strength to the actual yield strength of the rebar is greater than 1.25, the total elongation at full load is greater than 9%, the elongation is greater than 18%, the periodic etch corrosion test is less than 0.45 g / (m2h) And the salt corrosion test corrosion rate is smaller than 0.45 g / (m2h).
A preliminary desulfurization treatment step (S1) for molten iron controlling the sulfur content to 0.01% or less;
A converter smelting step (S2) in which molten iron, iron scrap and / or pig iron having been subjected to the step (S1) process are placed in a converter, smelting the content of carbon less than 0.05% and smelling less than 0.01%;
A step S3 for adding deoxidizing treatment to the Si and Mn alloying elements during the course of the lecture and adding the carbon powder and the coarse material;
A RH element is added to the RH vacuum refining furnace, oxygen is blown to remove C, the content of Cr and C elements is controlled to fall within the range described in the above item 1 or 2, and the deoxidizing process is performed using the LF furnace And the deoxidizing treatment is followed by addition of the alloying elements Mn, Mo, Sn and RE necessary for the steel component, further adding calcium iron alloy, blowing an inert gas and stirring the components, , An outdoor refining step (S4) for increasing the temperature of the molten steel and adding the coating agent;
A continuous casting step (S5) of continuously casting molten steel into a continuous casting slab through a continuous casting machine under the condition of protecting the casting; And
The continuous cast slab is heated to a temperature higher than the austenitizing temperature in a heating furnace and subjected to rough rolling, intermediate rolling and precision rolling, and a precision-rolled steel is placed on a cooling bed and air- And a rolling step (S6) of obtaining a reinforcing material of the reinforcing bars.
A preliminary desulfurization treatment step (S1) for molten iron controlling the sulfur content to 0.01% or less;
A converter smelting step (S2) in which molten iron, iron scrap and / or pig iron having been subjected to the step (S1) process are placed in a converter, smelting the content of carbon less than 0.05% and smelling less than 0.01%;
(S3) in which a deoxidizing treatment is carried out by adding Si and Mn alloying elements during the course of the lecture and carbon powder and a preservative are added;
The Cr element is added to the vacuum refining furnace, oxygen is blown to remove C, the Cr and C element content is controlled to fall within the range described in the third or fourth or fifth or sixth paragraph, Mo, Sn, RE and V and / or Ti, additionally calcium iron alloy is added, inert gas is blown into it, and the mixture is stirred An outdoor refining step (S4) of controlling the content of each element within the range defined in any one of claims 3 or 4 or 5 or 6, increasing the molten steel temperature and adding coating agent;
A continuous casting step (S5) of casting molten steel into a continuous casting slab through a continuous casting machine under conditions to protect the casting;
The continuous cast slab is heated to a temperature higher than the austenitizing temperature in the heating furnace and subjected to rough rolling, intermediate rolling and precision rolling, and a precision-rolled steel material is placed on the cooling bed to cool the air, And a rolling step (S6) of obtaining a reinforcing member of the component according to claim 6 or 6.
10. The method according to claim 8 or 9,
And in the step (S2), the tapping temperature is not higher than 1690 占 폚.
11. The method according to claim 8, 9 or 10,
And in step (S3), a protective gas is further blown in the lubrication process to stir the liquid steel.
The method according to any one of claims 8 to 11,
In the step S4, the temperature for blowing and decarburizing oxygen during the RH vacuum refining is 1605 DEG C or more, the temperature for refining and deoxidizing the LF furnace is 1575 DEG C or more, and the deoxidizing treatment in the LF furnace Wherein the oxygen content is controlled to 50 ppm or less, the soft agitation time is 5 minutes or more, and the molten steel temperature is raised to 1570 to 1600 占 폚.
13. The method according to any one of claims 8 to 12,
Wherein the rolling starting temperature before the rough rolling is 1030 to 1100 占 폚, the temperature during the precision rolling is 950 to 1050 占 폚, and the steel material is heated at a temperature of 1100 to 1200 占 폚 in the heating furnace at the step (S6) Lt; RTI ID = 0.0 &gt; 900-960 C. &lt; / RTI &gt;

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