CN113652614A

CN113652614A - Smelting method for producing phi 12-25mm HRB500E straight steel bar through microalloying

Info

Publication number: CN113652614A
Application number: CN202111022569.4A
Authority: CN
Inventors: 陈海军; 宋维兆; 王建新
Original assignee: Xinjiang Bayi Iron and Steel Co Ltd
Current assignee: Xinjiang Bayi Iron and Steel Co Ltd
Priority date: 2021-09-01
Filing date: 2021-09-01
Publication date: 2021-11-16
Anticipated expiration: 2041-09-01
Also published as: CN113652614B

Abstract

The invention discloses a smelting method for producing phi 12-25mm HRB500E straight steel bars by microalloying, which comprises the following chemical components: c: 0.19 to 0.25%, Si: 0.60-0.80%, Mn: 1.10-1.4%, S: less than or equal to 0.04 percent, P: less than or equal to 0.04 percent, N: 0.01-0.015%, Ti: 0.03-0.05%, V: 0.05 to 0.07 percent of Cr, 0.1 to 0.3 percent of Cr, less than or equal to 1.55 percent of the sum of the mass percent of Cr and Mn and less than or equal to 0.54 percent of Ceq; the smelting method comprises the following steps: adding a pre-deoxidation composite slag washing agent into converter tapping, wherein the slag washing agent comprises the following components in percentage by mass: 5-10% of fluorite, 65-75% of calcium carbide and 15-25% of limestone; the converter tapping is finished by adding the pre-deoxidation composite slag lotion, then the silicon-manganese alloy, the ferrosilicon and the high-carbon ferrochrome alloy are added in sequence, all the alloys need to be added when the tapping is carried out at 1/3, the alloys are completely added when the tapping is carried out at 3/4, the high-nitrogen composite reinforcer is added after the converter alloy is added, the adding amount is 0.6-0.8kg/t, and the converter alloy pre-deoxidation composite slag lotion comprises the following components: 12-20% of N, 18-25% of Ti, and soft blowing after the addition of ferrotitanium and vanadium-nitrogen alloy, wherein the soft blowing effect is that the exposed diameter of the steel slag-breaking molten steel is 100-200 mm.

Description

Smelting method for producing phi 12-25mm HRB500E straight steel bar through microalloying

Technical Field

The invention belongs to the technical field of metallurgy, and relates to a smelting method for producing phi 12-25mm HRB500E straight reinforcing steel bars by microalloying Ti, v, N and Cr which meet the requirements of GB/T1499.2-2018 standard.

Background

HRB500E is GB/T1499.2-2018 part 2 of steel bar for reinforced concrete: a steel bar brand specified in the hot-rolled ribbed steel bar is an old four-grade twisted steel bar, is a high-strength anti-seismic steel bar, and is a high-strength steel bar used on high-rise buildings and super high-rise buildings at present. The upper limits of C, Si, Mn, P and S elements and the upper limit of Ceq (carbon equivalent) are specified in GB/T1499.2-2018, and elements such as V, Nb and Ti can be added according to requirements; it is also specified that the content of N in the steel should be not more than 0.012%, that the content of N in the steel can be appropriately relaxed if a sufficient amount of N-binding element is present, and that an upper limit of the relaxation of the content of N is not specified. The structure of steel is mainly required to be ferrite and pearl structure, and tempered martensite structure should not be arranged on a base circle.

The hot-rolled ribbed steel bar is a production license product, and a refining furnace is required when steel billets for 500-grade anti-seismic hot-rolled ribbed steel bar and corrosion-resistant steel bar, 600-grade hot-rolled ribbed steel bar and various grades of stainless steel bars are produced according to the regulations of the construction Steel bar production license Specification.

HRB500E is generally based on HRB400E, the mechanical property index of HRB500E is satisfied by adding strengthening elements through conventional hot rolling or controlled cooling after rolling. HRB500E is mainly produced by a V-N microalloy strengthening technology in China, the V content is usually about 0.09 percent, which is basically one time of HRB400E, and the enterprise cost is very high. The vanadium-nitrogen alloy has high price and large fluctuation in recent years, and the vanadium-nitrogen alloy has continuous price expansion in 2018: the content of the active carbon is increased from 20 ten thousand yuan/ton at the beginning of the year to 80 ten thousand yuan/ton at 11 months, and is kept at about 15 ten thousand yuan/ton even at 5 months in 2021; this increases the cost of HRB500E much more than HRB 400E. The ferrotitanium alloy has low price which is stabilized to about 1 ten thousand yuan/ton for years. However, the reports of the titanium alloy strengthening production of HRB400E are few, and the titanium alloy strengthening production of HRB500E is more rarely reported, mainly because the chemical property of Ti element is very active and is very easy to react with oxygen in slag and steel in the smelting alloying process, so that the yield of Ti in the smelting process is low and unstable, and the production is difficult to control. The refining is helpful to improve the yield of Ti and has the functions of fine grain and strengthening in steel. The requirement of HRB500E production necessitates the presence of refining equipment, which provides convenient conditions for Ti microalloying to produce HRB 500E. Therefore, the V \ Ti composite micro-alloy reinforced 500 MPa-grade hot-rolled ribbed steel bar and the production process thereof are designed, and the method has practical significance for reducing the cost of enterprises and improving the market competitiveness.

A paper that the Vanshining Li JING Yang Chenli is published in Henan Metallurgic of 2017, volume 25, month 2, volume 1, "HRB 500E aseismic reinforcement production process and performance optimization" provides a component range for producing phi 12-phi 32mmHRB500E by vanadium-nitrogen microalloying, which is shown in Table 1

TABLE 1

According to the paper, V-N alloy strengthening is used, giving an upper limit for V. The control range of V according to the conventional analysis is equivalent to the alloy range of HRB500E produced in China, the cost is higher, and the paper suggests that the heating time of a heating furnace needs to be increased during rolling, which affects the rolling efficiency.

The article "development of high-strength aseismic reinforcement HRB 500E" published in Gansu metallurgy 2015, volume 6, month 37, and phase 3 of Liuyanglin. The article provides the compositional ranges of HRB500E with different specifications, see Table 2, and proposes the concept of extracting carbon, manganese, adding Cr elements, and producing HRB500E with properly reduced V content.

TABLE 2

Internal control brand

Specification mm

C%

Si%

Mn%

P，S%

Cr%

V%

Ceq%

HRB500E-1

10~12

0.21~0.25

0.3~0.5

1.35~1.50

≤0.035

Proper amount of

0.05~0.07

≤0.55

HRB500E-2

14~25

0.21~0.25

0.35~0.55

1.3~1.50

≤0.035

Proper amount of

0.06~0.08

≤0.55

HRB500E-3

28~32

0.20~0.24

0.4~0.55

1.35~1.55

≤0.035

Proper amount of

0.08~0.10

≤0.55

HRB500E-4

36~50

0.19~0.25

0.4~0.55

1.30~1.55

≤0.035

Proper amount of

0.10~0.12

≤0.55

According to Table 2, Si is 0.3 to 0.55%, Mn is 1.3 to 1.55%, and V (14 to 25 standard) is 0.06 to 0.08, although Cr is added, no specific amount is given for the Cr content. According to the paper, the cost of HRB500E is still high, the rolling speed needs to be controlled during rolling, the cooling mode of combining slight water penetration and air cooling is carried out after rolling, the temperature of an upper cooling bed after rolling is properly reduced, and the temperature of the upper cooling bed is controlled to be 980 +/-20 ℃. This requires control of the rolling speed and the presence of post-rolling water cooling equipment to ensure the temperature of the upper cooling bed.

GB/T1499.2-2018 stipulates that the metallographic structure of the steel bar should be mainly ferrite plus pearlite, and HRB500E is no exception. According to the introduction of microalloy non-quenched and tempered steel published by the publisher of metallurgical industry, edited by Dong Cheng Rui et al, the bainite transformation of steel is promoted when the Mn content exceeds 1.5% to 1.6%. Therefore, the Mn content should not exceed 1.5%. Cr and Mn are elements for increasing hardenability in steel. The simultaneous addition of Cr and Mn has the effect of improving the strength, but can also cause the appearance of a non-ferrite pearlite structure in a steel bar structure, easily cause brittle fracture of the steel bar during bending, and increase the quality risk.

Disclosure of Invention

The invention provides a smelting method for producing small-specification phi 12-25mmHRB500E by using Ti, V, N and Cr, which reduces the addition of expensive V-N alloy and realizes low-cost production.

The invention adopts the technical scheme that a smelting method for producing phi 12-25mm HRB500E straight steel bars by microalloying comprises the following chemical components in percentage by mass: c: 0.19 to 0.25%, Si: 0.60-0.80%, Mn: 1.10-1.4%, S: less than or equal to 0.04 percent, P: less than or equal to 0.04 percent, N: 0.01-0.015%, Ti: 0.03-0.05%, V: 0.05 to 0.07 percent of Cr, 0.1 to 0.3 percent of Cr, less than or equal to 1.55 percent of the sum of the mass percent of Cr and Mn and less than or equal to 0.54 percent of Ceq; the smelting method comprises the following steps: adding a pre-deoxidation composite slag washing agent into converter tapping, wherein the slag washing agent comprises the following components in percentage by mass: 5-10% of fluorite, 65-75% of calcium carbide and 15-25% of limestone; by adopting Ti and V composite microalloying smelting process technology and process steps, the adding time of Ti iron is controlled, new material for adding N in molten steel, namely high-nitrogen composite reinforcer, the higher Si content is controlled, Cr is added, Mn is reduced, and the small-specification phi 12-25mm HRB500E straight steel bars are produced by Ti and V composite microalloying: the end-point carbon content of the converter is less than or equal to 0.06 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 2.0; the carbon content at the end point of the converter is more than or equal to 0.07 percent and less than or equal to 0.08 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 1.5; the carbon content at the end point of the converter is more than 0.08 percent and less than or equal to 0.12 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 1.2; the carbon content at the end point of the converter is more than 0.12 percent and less than or equal to 0.14 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 1.0; the carbon content at the end point of the converter is more than 0.14 percent and less than or equal to 0.16 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 0.8; the carbon content at the end point of the converter is more than 0.16 percent and less than or equal to 0.20 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 0.6; the converter tapping is finished by adding the pre-deoxidation composite slag lotion, then the silicomanganese alloy, the ferrosilicon and the high-carbon ferrochrome alloy are sequentially added, the addition amount is set according to the component requirements, all the alloys must be added when tapping 1/3, the alloys are completely added when tapping 3/4, the high-nitrogen composite reinforcer is added after the converter alloy is added, the high-nitrogen composite reinforcer must be stirred by large argon during and after tapping, the addition amount of the high-nitrogen composite reinforcer is 0.6-0.8kg/t, and the components of the high-nitrogen composite reinforcer are as follows: the method comprises the following steps of adding 12-20% of N, 18-25% of Ti, soft blowing after adding ferrotitanium and vanadium-nitrogen alloy, wherein the soft blowing time is 5-7min, sampling and rapidly analyzing, and then fine-adjusting Ti, wherein the Ti content is adjusted by adopting titanium wire feeding in the fine-adjusting process, and the soft blowing effect is achieved by breaking the exposed diameter of the steel slag and the molten steel of 100 mm and 200 mm.

The steel bar produced by the method has the specification size of phi 12-25mm, the tensile strength of more than or equal to 630MPa, the yield strength of more than or equal to 500MPa, the yield ratio of less than or equal to 1.3, the strength-yield ratio of more than or equal to 1.25 and the maximum total elongation of more than or equal to 9.0 percent, and meets the requirements of the national standard GB/T1499.2-2018 part 2 of steel for reinforced concrete: hot rolled ribbed bar (HRB 500E).

The method comprises the following steps: 1. si is substantially dissolved in ferrite in steel and is present in inclusions. Dissolved in ferrite and can play a role in solid solution strengthening. Therefore, the Si content is designed to be 0.6-0.8% of the upper limit specified in GB/T1499.2-2018, and the function of Si is fully exerted. 2. In order to ensure that the steel bar structure mainly comprises ferrite and pearlite, the Mn content is properly reduced, Cr element is added, the sum of Cr and Mn content is controlled, Ceq is controlled to be less than or equal to 0.54%, and the welding performance of the steel bar is improved. The concrete requirements are as follows: the content range of Mn: 1.1-1.4%; the content range of Cr is as follows: 0.1-0.3%; the content of (Cr + Mn) is less than or equal to 1.55 percent. 3. Ti and V are compounded and strengthened, the content of V with high price is controlled in a lower range, and the effect of reducing the cost is achieved. The concrete requirements are as follows: the content range of V: 0.05-0.07%, and the content range of Ti is as follows: 0.03 to 0.05 percent. 4. Adding a high-nitrogen composite reinforcer to increase the nitrogen content of the molten steel and fully play the reinforcing role of Ti (CN) and V (CN); refining is carried out in the steelmaking process, and Ti iron is added in the later period of refining, so that the yield of Ti is improved. In order to strengthen Ti (CN) and V (CN), the content of N in the steel is controlled to be 0.010-0.015%. 5. The method adopts conventional rolling, and a water cooling process after rolling is not needed to produce the small-specification phi 12-25mm HRB500E straight steel bars.

The invention mainly adds the pre-deoxidation composite slag washing agent in the converter tapping, aiming at performing the pre-deoxidation function in the early stage of the tapping, the calcium carbide can be oxidized into CaO and CO2, the lime stone is decomposed into CaO and CO2 at high temperature, and the fluorite has the function of quickly forming a slag layer with low melting point and good adsorptivity with deoxidation products on the surface layer of the steel ladle, so that the early stage in the steel ladle has good dynamic conditions, and the surface layer of the steel ladle forms a thin protective slag layer.

The performance indexes of the chemical components of the steel bar produced by the method are shown in the table 3:

TABLE 3 chemical composition%

C

Si

Mn

P,S

Ti

Cr

N

V

Ceq

Design of

0.19～0.25

0.60～0.80

1.1～1.4

≤0.04

0.03～0.05

0.1～0.3

0.01～0.015

0.05～0.07

≤0.54

GB/T1499.2

≤0.25

≤0.8

≤1.6

≤0.045

/

≤0.55

Phi 12 mm-phi 25mm are produced according to the requirements of the invention. The sampling and detecting data are shown in tables 4 and 5

TABLE 4 sample composition case%

TABLE 5 sample Performance conditions

Serial number

Specification mm

Yield strength MPa

Tensile strength MPa

Total elongation of maximum force%

Ratio of yield to strength

Ratio of flexion to flexion

1

Φ12

532/534

691/689

14/13

1.3/1.29

1.06/1.07

2

Φ12

534/533

694/692

13.5/13.5

1.3/1.3

1.07/1.07

3

Φ12

536/544

695/699

14.5/14

1.3/1.28

1.07/1.09

4

Φ16

543/536

697/695

13.5/13.5

1.28/1.3

1.09/1.07

5

Φ16

536/537

694/696

13/12.5

1.29/1.3

1.07/1.07

6

Φ16

556/556

713/713

14/14.5

1.28/1.28

1.11/1.11

7

Φ22

544/548

691/694

13.5/14.5

1.27/1.27

1.09/1.1

8

Φ22

539/534

693/690

15/13.5

1.29/1.29

1.08/1.07

9

Φ22

546/550

693/700

14.5/14.5

1.27/1.27

1.09/1.1

10

Φ25

580/573

740/738

13.5/13.5

1.28/1.29

1.16/1.15

11

Φ25

544/541

691/690

13.5/14

1.27/1.28

1.09/1.08

12

Φ25

546/550

693/700

14.5/14.5

1.27/1.27

1.09/1.1

Detailed Description

A smelting method for producing phi 12-25mm HRB500E straight steel bars through microalloying comprises the following chemical components in percentage by mass: c: 0.19 to 0.25%, Si: 0.60-0.80%, Mn: 1.10-1.4%, S: less than or equal to 0.04 percent, P: less than or equal to 0.04 percent, N: 0.01-0.015%, Ti: 0.03-0.05%, V: 0.05 to 0.07 percent of Cr, 0.1 to 0.3 percent of Cr, less than or equal to 1.55 percent of the sum of the mass percent of Cr and Mn and less than or equal to 0.54 percent of Ceq; the smelting method comprises the following steps: adding a pre-deoxidation composite slag washing agent into converter tapping, wherein the slag washing agent comprises the following components in percentage by mass: 5-10% of fluorite, 65-75% of calcium carbide and 15-25% of limestone; by adopting Ti and V composite microalloying smelting process technology and process steps, the adding time of Ti iron is controlled, new material for adding N in molten steel, namely high-nitrogen composite reinforcer, the higher Si content is controlled, Cr is added, Mn is reduced, and the small-specification phi 12-25mm HRB500E straight steel bars are produced by Ti and V composite microalloying: the end-point carbon content of the converter is less than or equal to 0.06 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 2.0; the carbon content at the end point of the converter is more than or equal to 0.07 percent and less than or equal to 0.08 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 1.5; the carbon content at the end point of the converter is more than 0.08 percent and less than or equal to 0.12 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 1.2; the carbon content at the end point of the converter is more than 0.12 percent and less than or equal to 0.14 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 1.0; the carbon content at the end point of the converter is more than 0.14 percent and less than or equal to 0.16 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 0.8; the carbon content at the end point of the converter is more than 0.16 percent and less than or equal to 0.20 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 0.6; the converter tapping is finished by adding the pre-deoxidation composite slag lotion, then the silicomanganese alloy, the ferrosilicon and the high-carbon ferrochrome alloy are sequentially added, the addition amount is set according to the component requirements, all the alloys must be added when tapping 1/3, the alloys are completely added when tapping 3/4, the high-nitrogen composite reinforcer is added after the converter alloy is added, the high-nitrogen composite reinforcer must be stirred by large argon during and after tapping, the addition amount of the high-nitrogen composite reinforcer is 0.6-0.8kg/t, and the components of the high-nitrogen composite reinforcer are as follows: the method comprises the following steps of adding 12-20% of N, 18-25% of Ti, soft blowing after adding ferrotitanium and vanadium-nitrogen alloy, wherein the soft blowing time is 5-7min, sampling and rapidly analyzing, and then fine-adjusting Ti, wherein the Ti content is adjusted by adopting titanium wire feeding in the fine-adjusting process, and the soft blowing effect is achieved by breaking the exposed diameter of the steel slag and the molten steel of 100 mm and 200 mm.

Claims

1. A smelting method for producing phi 12-25mm HRB500E straight steel bars through microalloying is characterized in that the steel bars comprise the following chemical components in percentage by mass: c: 0.19 to 0.25%, Si: 0.60-0.80%, Mn: 1.10-1.4%, S: less than or equal to 0.04 percent, P: less than or equal to 0.04 percent, N: 0.01-0.015%, Ti: 0.03-0.05%, V: 0.05 to 0.07 percent of Cr, 0.1 to 0.3 percent of Cr, less than or equal to 1.55 percent of the sum of the mass percent of Cr and Mn and less than or equal to 0.54 percent of Ceq;

the smelting method comprises the following steps: adding a pre-deoxidation composite slag washing agent in a converter tapping stage, wherein the slag washing agent comprises the following components in percentage by mass: 5-10% of fluorite, 65-75% of calcium carbide and 15-25% of limestone; the end-point carbon content of the converter is less than or equal to 0.06 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 2.0; the carbon content at the end point of the converter is more than or equal to 0.07 percent and less than or equal to 0.08 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 1.5; the carbon content at the end point of the converter is more than 0.08 percent and less than or equal to 0.12 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 1.2; the carbon content at the end point of the converter is more than 0.12 percent and less than or equal to 0.14 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 1.0; the carbon content at the end point of the converter is more than 0.14 percent and less than or equal to 0.16 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 0.8; the carbon content at the end point of the converter is more than 0.16 percent and less than or equal to 0.20 percent, and the addition amount kg/t of the pre-deoxidation composite slag washing agent is 0.6; the method comprises the following steps of adding a pre-deoxidation composite slag washing agent after converter tapping is finished, then adding a silicon-manganese alloy, a silicon-iron alloy and a high-carbon ferrochrome alloy in sequence, wherein the addition amount is set according to component requirements, all the alloys need to be added when the converter tapping is 1/3, the alloys are completely added when the converter tapping is 3/4, a high-nitrogen composite reinforcer is added after the converter alloy is added, the addition amount of the high-nitrogen composite reinforcer is 0.6-0.8kg/t, and the components of the high-nitrogen composite reinforcer are as follows: the method comprises the following steps of adding 12-20% of N, 18-25% of Ti, soft blowing after adding ferrotitanium and vanadium-nitrogen alloy, wherein the soft blowing time is 5-7min, sampling and rapidly analyzing, and then fine-adjusting Ti, wherein the Ti content is adjusted by adopting titanium wire feeding in the fine-adjusting process, and the soft blowing effect is achieved by breaking the exposed diameter of the steel slag and the molten steel of 100 mm and 200 mm.