CN107974619A - Microalloy containing V builds steel bar and its production method - Google Patents

Abstract

The invention belongs to the field of iron and steel metallurgy, and in particular relates to a V-containing microalloy construction steel bar and a production method thereof. Aiming at the problems of low nitrogen content and few types of vanadium nitride alloys used in the preparation of nitrogen-containing alloy steels, the invention provides a V-containing microalloy building steel bar and a production method thereof. The composition of the bar is: by weight percentage, C: 0.15% to 0.30%, Si: 0.30% to 1.00%, Mn: 0.60% to 1.30%, N: 0.0060% to 0.0180%, P≤0.040%, S≤0.040%, V:0.010%～0.160%, the balance is Fe and unavoidable impurities. The key of its preparation method is to feed the N-containing cored wire on the small platform behind the furnace and adjust the N to a suitable level. The method of the invention has simple operation, high and stable nitrogen yield, and can effectively reduce the production cost, and is worthy of popularization and use.

Description

Containing V micro-alloyed construction steel bar and production method thereof

technical field

The invention belongs to the field of iron and steel metallurgy, and in particular relates to a V-containing microalloy construction steel bar and a production method thereof.

Background technique

Microalloyed steel mainly refers to the steel whose performance can be obviously improved by adding a small amount or a trace amount of certain elements in the steel, especially the strength index of the steel. Under the existing technical conditions, microalloyed steel is mainly obtained by adding a small amount or a small amount of vanadium, niobium and titanium. The mechanism of microalloying is: after adding vanadium, niobium and titanium as trace elements into molten steel, they combine with carbon and nitrogen in molten steel to form carbon and nitrogen compound particles, namely V(C, N), Nb( C, N) and Ti (C, N) particles, these particles have a certain effect of precipitation strengthening and grain refinement, which can significantly improve the strength of steel.

It can be seen from this that in fact, the role of microalloyed steel vanadium, niobium and titanium is inseparable from nitrogen, but in general, converters are used to smelt steel, and the residual nitrogen content is in the range of 0.0030% to 0.065%. For smelting steel, the residual nitrogen content is in the range of 0.050% to 0.085%, in most cases. In order to give full play to the role of vanadium, niobium and titanium, it is necessary to add nitrogen to achieve it.

In the early days, nitrogen was added to microalloyed steels by adding 3% to 6% of nitrided alloys. However, due to the low nitrogen content of nitrided alloys, the amount of alloy added was large and the yield was unstable. Gradually replaced by vanadium nitride alloys with higher nitrogen content. At present, it is almost difficult to use 3% to 6% nitrided alloys in the production of microalloyed steels, and almost all of them use vanadium-containing and high-nitrogen vanadium nitride alloys. Vanadium nitride alloys mainly have three grades: VN12, VN14 and VN16. In general, the ratios of nitrogen and vanadium of the three grades are basically fixed, respectively 12:78(N:V); 14:78(N:V); 16:78(N:V), namely nitrogen and vanadium The highest ratio of VN16 is 16:78, that is, the alloy contains 16% N and 78% vanadium. Although vanadium nitride alloys contain both vanadium and high nitrogen content, for different microalloying technology routes in microalloyed steels, especially composite microalloyed steels, such as V-Ti-N, or even V-Ti-Nb -N, also cannot meet the demand.

Contents of the invention

Aiming at the problems of low nitrogen content and few types of vanadium nitride alloys selected for preparing nitrogen-containing alloy steels, the invention provides a new method for preparing nitrogen-containing alloys. The method adopts the method of adding nitrogen-containing cored wire to precisely control the nitrogen content, and the nitrogen yield is high.

The technical solution of the present invention to solve the above-mentioned technical problems is: to provide a V-containing micro-alloyed construction steel bar and a production method thereof.

The invention provides a V-containing microalloy building steel bar, the chemical composition of which is: by weight percentage, C: 0.15% to 0.30%, Si: 0.30% to 1.00%, Mn: 0.60% to 1.30%, N: 0.0060%～0.0180%, P≤0.040%, S≤0.040%, V: 0.010%～0.160%, the balance is Fe and unavoidable impurities.

The present invention also provides a method for producing the above-mentioned V-containing microalloyed construction steel bar, comprising the following steps:

The molten iron in the blast furnace is smelted in a converter and continuously cast to produce a billet; the billet is heated, rolled into a continuous bar rolling production line, and cooled to form a round bar or ribbed steel bar; the core is fed into the ladle on the small platform behind the furnace Line adjustment N, billet heating temperature controlled to 950-1220°C, soaking temperature controlled to 1000-1200°C, total heating and soaking time 90-120min; the composition of the billet is: by weight percentage, C: 0.15%~ 0.30%, Si: 0.30% ~ 1.00%, Mn: 0.60% ~ 1.30%, N: 0.0060% ~ 0.0180%, P≤0.040%, S≤0.040%, V: 0.010% ~ 0.160%, the balance is Fe and unavoidable impurities.

Further, the production method of the above-mentioned V-containing microalloyed construction steel bar comprises the following steps:

a. Converter smelting

Add molten iron and scrap steel into the converter, use the converter to blow oxygen to remove C, and carry out smelting. When the C content of the molten steel is 0.05% to 0.15%, the P content is ≤0.025%, the S content is ≤0.035%, and the molten steel temperature is ≥1650°C, the steel is tapped;

When tapping 1/3-2/3, add FeSi, FeMn alloy and recarburizer, FeV or VN alloy, control C at 0.15%-0.30%, Si at 0.30%-1.00%, and Mn at 0.60%-1.30% , V is 0.010% to 0.160%;

b. Feed cored wire

After the steel is tapped, it is transferred to the ladle. After the ladle reaches the small platform behind the furnace, an inert gas is blown into the ladle, and a cored wire containing N is added to control the N content in the molten steel to 0.0060% to 0.0180%;

c. Continuous casting

Control the superheat degree of the tundish in the continuous casting machine to 20-50°C, continuously cast the molten steel billet into a billet with a cross-section of 150mm×150mm-200mm×200mm, and air-cool it to room temperature;

d. Billet heating and rolling

The billet heating temperature is controlled at 950-1220°C, the soaking temperature is controlled at 1000-1200°C, the total heating and soaking time is 90-120 minutes, and the continuous bar rolling production line is used to roll into round bars or ribbed steel bars.

Wherein, in the production method of the above-mentioned V-containing microalloyed construction steel bar, the molten iron in step a requires that the S content is ≤0.060%.

Wherein, in the above-mentioned production method of V-containing microalloyed construction steel rods, the FeSi and FeMn alloys in step a are replaced by FeSiMn alloys.

Wherein, in the production method of the above-mentioned V-containing microalloyed construction steel bar, the inert gas described in step b is one of argon or nitrogen.

Wherein, in the production method of the above-mentioned V-containing micro-alloyed construction steel rod, the time for injecting the inert gas in step b is ≥ 2 minutes.

Wherein, in the production method of the above-mentioned V-containing micro-alloyed construction steel bar, the exit temperature of step b is 60-90° C. higher than the liquidus temperature of the steel.

Wherein, in the production method of the above-mentioned V-containing microalloyed construction steel bar, the specification of the round bar or ribbed steel bar described in step d is

The beneficial effects of the present invention are:

The present invention designs a V-containing micro-alloy building steel bar, adds alloy composition V: 0.010% to 0.160% in the steel, and then adjusts the steel type N by feeding the N-containing cored wire after converter smelting. content, rolled by a bar rolling production line, and finally a micro-alloyed construction steel bar with high strength and high nitrogen yield can be prepared. The method of the invention has simple operation, high and stable nitrogen yield, and can effectively reduce the production cost, and is worthy of popularization and use.

Detailed ways

The invention provides a V-containing microalloy building steel bar, the chemical composition of which is: by weight percentage, C: 0.15% to 0.30%, Si: 0.30% to 1.0%, Mn: 0.60% to 1.30%, N : 0.0060%～0.0180%, P≤0.040%, S≤0.040%, V: 0.010%～0.160%, the balance is Fe and unavoidable impurities.

The purpose of adding 0.010%-0.160% V in the present invention is to ensure the aging performance of the steel. Generally, when steel is smelted by converter, the residual nitrogen content in the final finished steel is in the range of 0.0030% to 0.0065%, and when steel is smelted by electric furnace, the residual nitrogen content is in the range of 0.0050% to 0.0085%. As the N content in the steel increases, the timeliness becomes worse. The present invention adopts the method of adding 0.010% to 0.160% V to ensure the timeliness of the steel, and at the same time give full play to the solid solution strengthening effect of nitrogen. Thereby increasing the strength of the steel and reducing the cost of the alloy of the steel.

In addition, in the above chemical composition, because the nitrogen content in molten steel is higher than the residual nitrogen content in ordinary steel, the addition of titanium is also easier to form V (C, N) particles, thereby promoting the precipitation of V, and can more fully exert vanadium. Precipitation strengthening and grain refinement to improve the comprehensive mechanical properties of steel, and reduce the amount of vanadium used under the premise of the same mechanical properties.

The present invention also provides a production method of V-containing micro-alloyed construction steel bars, comprising the following steps:

a. Converter smelting

First, add molten iron and steel scrap into the converter. It is required that the S content of the added molten iron is not more than 0.060%. To 0.05% ~ 0.15% of C, P is not more than 0.025%, S is not more than 0.035%, and the steel is tapped into the ladle when the tapping temperature is not lower than 1650°C;

Add FeSi alloy containing Si element, FeMn alloy containing Mn element, and alloy containing V element and recarburizing agent during the tapping process. The recarburizing agent is C powder or anthracite, and the C is controlled in the range of 0.15% to 0.30%. Inside, control Si in the range of 0.30% to 1.00%, control Mn in the range of 0.60% to 1.30%, control V in the range of 0.010% to 0.160%; start adding FeSi, FeMn and FeV or For VN alloy, it must be added when the steel is tapped to 2/3;

In the addition of the above alloys, FeSiMn alloys containing Si and Mn can also be used instead of FeSi and FeMn alloys;

b. Inert gas is blown into the converter and the cored wire is fed

When tapping is completed, the ladle is immediately connected to the pipeline, and inert gas is blown into the molten steel in the ladle. The inert gas blown in can be argon or nitrogen, and the time for blowing inert gas should not be less than 2 minutes. ; The inert gas blowing time is specified to be not less than 2 minutes to ensure that the molten steel has sufficient circulation time to fully melt and homogenize the various alloys added;

After blowing inert gas for more than 2 minutes, take samples for N content detection, and add N-containing cored wire by feeding the wire according to the test results. The N-containing cored wire is mainly N-containing alloys, such as SiN, etc., and control the molten steel The N content in the medium is in the range of 0.0060% to 0.0180%. If the N content control in the molten steel after the furnace is relatively stable, it is not necessary to take a sample for N content detection, and directly feed the cored wire;

Before feeding the cored wire, the ladle needs to be connected to the pipe for blowing inert gas again, and the inert gas can only be fed into the cored wire containing N. The inert gas can be argon or nitrogen. After the line feeding is completed, the time for blowing inert gas needs to be extended by more than 2 minutes to ensure the uniformity of N elements in the molten steel and to control the temperature of the molten steel out of the station;

Measure the temperature before exiting the station to ensure that the exiting temperature is 60-90°C higher than the liquidus temperature of the steel;

c. Continuous casting into billets

Control the superheat degree of the tundish of the continuous casting machine to 20-50°C, which is achieved through the control of the above-mentioned converter tapping and post-station temperature control;

The cross-section of the steel billet made by molten steel continuous casting is 150mm×150mm～200mm×200mm. The small cross-section of the billet below 150mm×150mm is not conducive to the continuous operation of the converter process, and the cross-section of the billet larger than 200mm×200mm will prolong the subsequent Heating time when rolling billets;

The steel billet made by continuous casting of molten steel is naturally cooled to room temperature in the air;

d. Billet heating and rolling

The heating of the billet requires a total heating time of 90-120 minutes, the maximum heating temperature of the heating furnace is 1220°C, the maximum soaking temperature is 1200°C, and the temperature of the billet out of the heating furnace is controlled within the range of 1000-1200°C;

The final product specification is The round bar, or the shape of the ribbed steel bar specified in GB 1499.2 Ribbed steel bars for construction can be rolled by a continuous bar rolling production line.

The following will further explain the specific implementation of the present invention through examples, but it does not mean that the protection scope of the present invention is limited to the scope described in the examples.

Embodiment 1 uses the inventive method to prepare containing V microalloy building steel bars

A steel plant adopts the technology of the present invention to produce ribbed steel bars for construction in the converter process with a nominal capacity of 120 tons (the actual steel output is in the range of 120 to 140 tons). The production process is converter smelting → blowing inert gas after the furnace + feeding Core-spun wire → 6-machine 6-strand billet continuous casting machine casting into 150mm×150mm billet → billet heating → rolling into continuous bar rolling production line Ribbed steel bars.

Firstly, 120 tons of molten iron and 20 tons of scrap steel are added into the converter, and the S content of the added molten iron is 0.047%. After the molten iron and steel scrap are added to the converter, the molten iron and steel scrap are initially smelted into molten steel by using the function of the converter to remove C by blowing oxygen. When the composition of the molten steel is initially smelted to 0.09% C, 0.020% P, and 0.025% S, the temperature is 1676°C When tapping into the ladle, the actual tapping amount is 136 tons (about 5% of the raw material is burned in the converter smelting process). Add FeSi, FeMn, FeV alloy and anthracite to the molten steel during the tapping process to carry out alloying of Si, Mn, V and C elements, wherein the content of Si in the added FeSi alloy is 74%, and the content of Mn in the FeMn alloy is 82%. The V content in the FeV alloy is 78%, the fixed C in the anthracite is 92%, the Si content in the molten steel is controlled to be 0.30%, the Mn content is 0.60%, the V content is 0.011%, and the C content is 0.15%. .

After the molten steel reaches the small platform behind the furnace, the ladle is immediately connected to the pipeline, and nitrogen gas is blown into the molten steel in the ladle. After blowing nitrogen gas for 4 minutes, the N-containing cored wire is added by feeding the wire, and the N content in the molten steel is controlled to 0.0064 %.

After feeding the cored wire, continue to blow in nitrogen for 2 minutes before measuring the temperature. Determine the time to continue blowing nitrogen according to the temperature measurement results to adjust the temperature of the molten steel. Measure the temperature again before leaving the station. When the temperature of the molten steel is 1671°C, leave the station and The molten steel is sent to the continuous casting machine for casting.

Cast billets of 150mm×150mm on a 6-machine, 6-strand billet continuous casting machine. During continuous casting, the temperature of the tundish is 1549°C, and the liquidus temperature of the steel is 1515°C. Sampling and analysis of the chemical composition of molten steel in the continuous casting machine 0.15% C, 0.30% Si, 0.63% Mn, 0.03% Cr, 0.010% V, 0.038% P, 0.028% S, 0.0061% N, the rest is Fe and other unavoidable impurities . The slab stack is naturally cooled to room temperature.

After the slab is cooled, it is sent to the continuous bar production line for heating and rolling. The rolling specification is ribbed steel bars. The billet heating temperature is 1213°C, the soaking temperature is 1182°C, the total heating time reaches 95 minutes, and then it is rolled out of the furnace. The final rolling temperature is 955°C, and it is naturally air-cooled after being placed on the cooling bed, and finally collected and bundled.

The test results of the mechanical properties of the steel are: ReL (Rp0.2) is 346MPa, the tensile strength is 452MPa, the elongation is 37.1%, and the total elongation of the maximum force is 17.4%. Bend qualified. The structure of steel is ferrite + pearlite.

Example 2 Preparation of V-containing microalloyed building steel bars by the method of the present invention

A steel plant adopts the technology of the present invention to produce ribbed steel bars for construction in the converter process with a nominal capacity of 120 tons (the actual steel output is in the range of 120 to 140 tons). The production process is converter smelting → blowing inert gas after the furnace + feeding Core-spun wire → 6-machine 6-strand billet continuous casting machine casting into 150mm×150mm billet → billet heating → rolling into continuous bar rolling production line Ribbed steel bars.

Firstly, 120 tons of molten iron and 20 tons of scrap steel are added into the converter, and the S content of the added molten iron is 0.042%. After the molten iron and steel scrap are added to the converter, the molten iron and steel scrap are initially smelted into molten steel by using the function of the converter to remove C by blowing oxygen. When the composition of the molten steel is initially smelted to 0.06% C, 0.020% P, and 0.025% S, the temperature is 1683°C When tapping into the ladle, the actual tapping amount is 131 tons (about 5% of the raw material is burned in the converter smelting process). Add FeSi, FeMn, FeV alloy and anthracite to the molten steel during the tapping process to carry out alloying of Si, Mn, V and C elements, wherein the content of Si in the added FeSi alloy is 74%, and the content of Mn in the FeMn alloy is 82%. The V content in the FeV alloy is 78%, the fixed C in the anthracite is 92%, the Si content in the controlled molten steel is 0.95%, the Mn content is 1.29%, the V content is 0.156%, and the C content is 0.29%.

After the molten steel reaches the small platform behind the furnace, the ladle is immediately connected to the pipeline, and nitrogen gas is blown into the molten steel in the ladle. After blowing nitrogen gas for 4 minutes, the N-containing cored wire is added by wire feeding method, and the N content in the molten steel is controlled at 0.0164 % range.

After feeding the cored wire, continue to blow nitrogen for 2 minutes before measuring the temperature. Determine the time to continue blowing nitrogen according to the temperature measurement results to adjust the temperature of the molten steel. Measure the temperature again before leaving the station. When the temperature of the molten steel reaches 1677°C, leave the station and The molten steel is sent to the continuous casting machine for casting.

Cast billets of 200mm×200mm on a 6-machine, 6-strand billet continuous casting machine. During continuous casting, the temperature of the tundish is 1530 ° C, and the liquidus temperature of the steel is 1495 ° C. Sampling and analysis of the chemical composition of molten steel in the continuous casting machine 0.30% C, 0.98% Si, 1.29% Mn, 0.03% Cr, 0.156% V, 0.034% P, 0.022% S, 0.0162% N, the rest is Fe and other unavoidable impurities . The slab stack is naturally cooled to room temperature.

After the slab is cooled, it is sent to the continuous bar production line for heating and rolling. The rolling specification is ribbed steel bars. The billet heating temperature is 1032°C, the soaking temperature is 1005°C, the total heating time reaches 95 minutes, and then it is rolled out of the furnace. The final rolling temperature is 881°C, and it is naturally air-cooled after being placed on the cooling bed, and finally collected and bundled.

The test results of the mechanical properties of the steel are: ReL (Rp0.2) is 536MPa, the tensile strength is 702MPa, the elongation is 17.3%, the maximum total elongation is 12.3%, and the cold bending at 180°C is qualified. The structure of steel is ferrite + pearlite.

Example 3 Preparation of V-containing microalloyed building steel bar by the method of the present invention

A steel plant adopts the technology of the present invention to produce ribbed steel bars for construction in the converter process with a nominal capacity of 120 tons (the actual steel output is in the range of 120 to 140 tons). The production process is converter smelting → blowing inert gas after the furnace + feeding Core-spun wire→6-machine 6-strand billet continuous casting machine casting into 150mm×150mm steel billet→steel billet heating→rolling into continuous bar rolling production line Ribbed steel bars.

Firstly, 120 tons of molten iron and 20 tons of scrap steel are added into the converter, and the S content of the added molten iron is 0.051%. After the molten iron and steel scrap are added to the converter, the molten iron and steel scrap are initially smelted into molten steel by using the function of the converter to remove C by blowing oxygen. When the composition of the molten steel is initially smelted to 0.06% C, 0.020% P, and 0.025% S, the temperature is 1681°C When tapping into the ladle, the actual tapping amount is 134 tons (about 5% of the raw material is burned in the converter smelting process). Add FeSi, FeMn, FeV alloy and anthracite to the molten steel during the tapping process to carry out alloying of Si, Mn, V and C elements, wherein the content of Si in the added FeSi alloy is 74%, and the content of Mn in the FeMn alloy is 82%. The V content in the FeV alloy is 78%, the fixed C in the anthracite is 92%, and the Si content in the controlled molten steel is 0.64%, the Mn content is 0.96%, the V content is 0.080%, and the C content is 0.21%.

After the molten steel reaches the small platform behind the furnace, the ladle is immediately connected to the pipeline, and nitrogen gas is blown into the molten steel in the ladle. After blowing nitrogen gas for 4 minutes, the N-containing cored wire is added by feeding the wire, and the N content in the molten steel is controlled at 0.0132 %.

After feeding the cored wire, continue to blow nitrogen for 2 minutes before measuring the temperature. Determine the time to continue blowing nitrogen according to the temperature measurement results to adjust the temperature of the molten steel. Measure the temperature again before leaving the station. When the temperature of the molten steel is 1665°C, leave the station and put The molten steel is sent to the continuous casting machine for casting.

Cast billets of 150mm×150mm on a 6-machine 6-strand billet continuous casting machine. During continuous casting, the temperature of the tundish is 1532°C, and the liquidus temperature of the steel is 1510°C. Sampling and analysis of the chemical composition of molten steel in the continuous casting machine 0.21% C, 0.67% Si, 0.97% Mn, 0.03% Cr, 0.080% V, 0.033% P, 0.022% S, 0.0131% N, the rest is Fe and other unavoidable impurities . The slab stack is naturally cooled to room temperature.

After the slab is cooled, it is sent to the continuous bar production line for heating and rolling. The rolling specification is ribbed steel bars. The billet heating temperature is 1137°C, the soaking temperature is 1115°C, the total heating time reaches 95 minutes, and then it is rolled out of the furnace. The final rolling temperature is 919°C, and it is naturally air-cooled after being placed on the cooling bed, and finally collected and bundled.

The test results of the mechanical properties of the steel are: ReL (Rp0.2) is 433MPa, tensile strength is 581MPa, elongation is 22.9%, the maximum total elongation is 15.4%, and the cold bending at 180°C is qualified. The structure of steel is ferrite + pearlite.

Claims (9)

1. microalloy containing V builds steel bar, it is characterised in that chemical composition is：By weight percentage, C：0.15%~ 0.30%th, Si：0.30%~1.00%, Mn：0.60%~1.30%, N:0.0060%~0.0180%, P≤0.040%, S ≤ 0.040%, V:0.010%~0.160%, surplus is Fe and inevitable impurity.

2. the production method of the building steel bar of microalloy containing V described in claim 1, it is characterised in that comprise the following steps：

It is blast-melted that steel billet is made through converter smelting, continuous casting；Steel billet is heated, the rolling of continous way rolling bar production line is become a useful person, Pole or Ribbed Bar is made in cooling；Core-spun yarn adjustment N, billet heating temperature control are fed in the ladle of chain-wales wherein after stove 950~1220 DEG C are made as, soaking temperature control is 1000~1200 DEG C, heating and 90~120min of soaking total time；The steel Base component is：By weight percentage, C：0.15%~0.30%, Si：0.30%~1.00%, Mn：0.60%~1.30%, N:0.0060%~0.0180%, P≤0.040%, S≤0.040%, V:0.010%~0.160%, surplus is Fe and can not The impurity avoided.

3. the production method of the building of microalloy containing V steel bar according to claim 2, it is characterised in that including following step Suddenly：

A, converter smelting

Molten iron and steel scrap are added in converter, C is taken off using Converter Oxigen Blowing, is smelted, treat molten steel C content for 0.05%~ 0.15%, P content≤0.025%, S content≤0.035%, when liquid steel temperature >=1650 DEG C, tap；

Tap 1/3-2/3 when, add FeSi, FeMn alloy and carburant, FeV or VN alloys, control C be 0.15%~ 0.30%th, Si is that 0.30%~1.00%, Mn is that 0.60%~1.30%, V is 0.010%~0.160%；

B, core-spun yarn is fed

It is transferred to ladle after tapping, ladle is reached after stove after chain-wales, and inert gas is blown into ladle, adds core-spun yarn containing N, is controlled N content is 0.0060%~0.0180% in molten steel processed；

C, continuous casting

It is 20~50 DEG C to control the degree of superheat wrapped in conticaster, the steel billet section that molten steel is casting continuously to form for 150mm × 150mm~ The square billet of 200mm × 200mm, is air-cooled to room temperature；

D, heating steel billet and rolling

Billet heating temperature control is 950~1220 DEG C, and soaking temperature control is 1000~1200 DEG C, heating and soaking total time For 90~120min, pole or Ribbed Bar are rolled into using continous way rolling bar production line.

4. the production method of the building of microalloy containing V steel bar according to claim 3, it is characterised in that：Described in step a Molten iron requires S content≤0.060%.

5. the production method of the building of microalloy containing V steel bar according to claim 3, it is characterised in that：Described in step a FeSi and FeMn alloys FeSiMn alloy replacings.

6. the production method of the building of microalloy containing V steel bar according to claim 3, it is characterised in that：Described in step b Inert gas be one kind in argon gas or nitrogen.

7. the production method of the building of microalloy containing V steel bar according to claim 3, it is characterised in that：Described in step b It is blown into time >=2min of inert gas.

8. the production method of the building of microalloy containing V steel bar according to claim 3, it is characterised in that：The outbound temperature of step b Liquidus temperature 60~90 DEG C of the degree higher than steel.

9. the production method of the building of microalloy containing V steel bar according to claim 3, it is characterised in that：Described in step d The specification of pole or Ribbed Bar is