CN117230366A

CN117230366A - Hot rolled ribbed steel bar produced by double high bars

Info

Publication number: CN117230366A
Application number: CN202311052389.XA
Authority: CN
Inventors: 陈学良; 周从锐; 庞锐; 熊良友; 金梁; 李顺奎; 钱学海
Original assignee: Guangxi Liuzhou Iron and Steel Group Co Ltd; Guangxi Liugang Huachuang Technology R&D Co Ltd
Current assignee: Guangxi Liuzhou Iron and Steel Group Co Ltd; Guangxi Liugang Huachuang Technology R&D Co Ltd
Priority date: 2022-05-27
Filing date: 2022-05-27
Publication date: 2023-12-15
Also published as: CN115011875A; CN115011875B

Abstract

The invention provides a hot rolled ribbed steel bar produced by double high bars, which comprises the following components in percentage by weight: 0.21 to 0.25 percent, si:0.40 to 0.70 percent, mn:1.10 to 1.30 percent, P is less than or equal to 0.045 percent, S is less than or equal to 0.045 percent, and the balance is Fe; the specification of the hot rolled ribbed steel bar is phi 10-phi 20mm, and two-splitting rolling is adopted; the yield strength of the hot rolled ribbed steel bar is more than or equal to 440Mpa, the tensile strength is more than or equal to 600Mpa, the elongation after fracture A is more than or equal to 25%, the maximum total elongation Agt is more than or equal to 13%, and the strength-to-deflection ratio is more than or equal to 1.33.

Description

Hot rolled ribbed steel bar produced by double high bars

The invention is a divisional application, the application number of the mother application: 2022105947479, name of invention: the method for producing the hot rolled ribbed steel bar by the double high bars comprises the following steps of: 2022, 5 and 27.

Technical Field

The invention relates to the field of steel rolling, in particular to a hot rolled ribbed steel bar produced by double high bars.

Background

Hot rolled ribbed bars are the largest steel materials used in the world, and are widely used in highways, bridges and various constructions, as part 2 of steel for reinforced concrete, GB/T1499.2-2018: in the standard, the metallographic structure of the steel bar is mainly ferrite and pearlite, and tempered martensite structure does not appear on a base circle, which means that the process path for obtaining tempered sorbite by self tempering after water cooling is used for improving the strength of the steel bar is not feasible, most of steel factories currently add micro-alloys such as Nb, V and Ti into the steel to improve the strength of the steel bar by means of solid solution strengthening, fine grain strengthening, precipitation strengthening and the like, but the adding of the micro-alloys such as Nb, V and Ti can obviously improve the alloy cost and reduce the profit of enterprises.

In summary, the following problems exist in the prior art: and (3) producing the hot-rolled ribbed steel bar which does not have tempered martensite and sorbite structures and meets the standard of the hot-rolled ribbed steel bar without adding micro-alloys such as Nb, V and Ti.

Disclosure of Invention

The invention provides a method for producing hot rolled ribbed steel bars by double high bars (namely a method for producing hot rolled ribbed steel bars by double high-speed bars), which aims to solve the problem that hot rolled ribbed steel bars with qualified performances and without tempered martensite structures and sorbite structures are produced under the condition of not adding micro alloys such as Nb, V, ti and the like.

To this end, the present invention proposes a method of producing hot rolled ribbed steel bar with double high bars, the method of producing hot rolled ribbed steel bar with double high bars comprising:

the hot rolled ribbed steel bar comprises the following components in percentage by weight: 0.21 to 0.25 percent, si:0.40 to 0.70 percent, mn:1.10 to 1.30 percent, P is less than or equal to 0.045 percent, S is less than or equal to 0.045 percent, and the balance is Fe;

the specification of the hot rolled ribbed steel bar is phi 10-phi 20mm;

the production method adopts two-segmentation rolling, and comprises the following steps: blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, billet continuous casting, heating by a heating furnace, rough rolling, middle rolling, front water tank (2) before finish rolling and recovery sections, finish rolling, front water tank (2) before reducing, shearing multiple length, cooling bed, shearing fixed length, collecting and bundling;

wherein the initial rolling temperature is 950-1000 ℃, the finish rolling temperature is 900-930 ℃, the reducing temperature is 830-870 ℃, and the rolling is naturally cooled.

Further, after BOF blowing, molten iron is tapped by adopting a sliding plate slag blocking, then alloy and deoxidizing agent are added, so that the content of C is 0.21-0.25%, the content of Si is 0.40-0.70%, the content of Mn is 1.10-1.30%, the content of P, S is less than or equal to 0.045%, and then the molten iron is sent to an argon station for argon blowing, and the whole-process protection casting process is adopted for casting.

Further, the interior of the heating furnace is divided into four areas, namely a preheating area (section), a first heating area (section) and a second heating area (section), a soaking area (section), wherein the temperature of the first heating area is controlled between 1000 and 1060 ℃, the temperature of the second heating area is controlled between 1060 and 1120 ℃, the soaking area is controlled between 1040 and 1100 ℃, the initial rolling temperature is controlled between 950 and 1000 ℃, the finishing rolling temperature is controlled between 900 and 930 ℃, the reducing rolling temperature is controlled between 830 and 870 ℃, and the heating area is naturally cooled after rolling.

Further, the 2 water tanks before entering the finishing mill are all provided with 40% -80% of water. . Further, the 2 water tanks in front of the reducing mill are all opened with 20% -50% of water, and the water quantity is only used for controlling the temperature in the rolling process, so that the excessive temperature is prevented, the crystal grains grow up, and the water quantity of the through water cooling is not reached. The cooling is weak cooling after rolling, the diameter-entering and reducing temperature is controlled to be 830-870 ℃, and the surface of the steel bar cannot be provided with tempered sorbite tissues and martensitic tissues.

Further, the rolling speed is 14m/s-42m/s.

Further, the specification of the finished product is phi 10mm, and the rolling speed is 40m/s; the specification of the finished product is phi 12mm, and the rolling speed is 36m/s; the specification of the finished product is phi 14mm, and the rolling speed is 27m/s; the specification of the finished product is phi 16mm, and the rolling speed is 23m/s; the specification of the finished product is phi 18mm, and the rolling speed is 16m/s; or the specification of the finished product is phi 20mm, and the rolling speed is 15m/s.

Further, the hot rolled ribbed steel bar comprises the following components: c:0.22% >, si:0.48%, mn:1.18%, P:0.027%, S:0.031% and the balance of Fe.

Further, the hot rolled ribbed steel bar comprises the following components: c:0.23%, si:0.45%, mn:1.18%, P:0.041%, S:0.026% and the balance of Fe.

Further, the initial rolling temperature is controlled at 990 ℃, the finish rolling K2 temperature is 916 ℃, the reducing temperature is 846 ℃, and the product is naturally cooled by a cooling bed.

Further, the initial rolling temperature is controlled to be 984 ℃, the finish rolling K2 temperature is 919 ℃, the reducing temperature is 857 ℃, and the product is naturally cooled on a cooling bed.

Further, the temperature of the first heating section is controlled to 1012 ℃, the temperature of the second heating section is controlled to 1097 ℃, the temperature of the soaking section is controlled to 1059 ℃, and the heating time is 82 minutes.

The invention also provides a hot rolled ribbed steel bar produced by the double high bars, which comprises the following components in percentage by weight: 0.21 to 0.25 percent, si:0.40 to 0.70 percent, mn:1.10 to 1.30 percent, P is less than or equal to 0.045 percent, S is less than or equal to 0.045 percent, and the balance is Fe;

the specification of the hot rolled ribbed steel bar is phi 10-phi 20mm, and two-split rolling is adopted.

Further, the method for producing the hot rolled ribbed steel bar produced by the double high bars comprises the following steps: blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, billet continuous casting, heating by a heating furnace, rough rolling, middle rolling, a water tank (2) before finish rolling and a recovery section, a finish rolling, a water tank (2) before reducing, a recovery section, reducing, shearing multiple length, a cooling bed, shearing fixed length, collecting and bundling.

Further, the hot rolled ribbed steel bar of the invention has a metallographic structure of: macroscopic organization: no loop; surface layer tissue: p+f (pearlite+ferrite); 1/4 tissue: p+f (pearlite+ferrite); grain size at 1/4: 11.0-12 stages; 34% -41% of P (pearlite) content at 1/4 position; center organization: P+F.

Further, the yield strength of the hot rolled ribbed steel bar is more than or equal to 440Mpa, the tensile strength is more than or equal to 600Mpa, the elongation after fracture A is more than or equal to 25%, the maximum total elongation Agt is more than or equal to 13%, and the strength-to-deflection ratio is more than or equal to 1.33.

Further, the hot rolled ribbed steel bar of the invention has a yield strength: 445M-470pa, tensile strength: 610-630Mpa, elongation after break a:27% -31%, maximum force total elongation Agt: 13.9-18% and 1.34-1.36% of strong buckling ratio.

The invention can fully utilize the fine grain strengthening effect of controlled rolling and cooling, reduce the use amount of micro alloys such as Nb, V, ti and the like, and obtain the hot rolled ribbed steel bar which has no tempered martensite and sorbite structure and meets the standard of the hot rolled ribbed steel bar. The yield strength is more than or equal to 440Mpa, the tensile strength is more than or equal to 600Mpa, the elongation after breaking A is more than or equal to 25%, the maximum total elongation Agt is more than or equal to 13%, and the strength-to-deflection ratio is more than or equal to 1.33. The alloy cost of the ton steel is reduced to 65 yuan, and meanwhile, the manual input alloy amount of a converter can be reduced, and the labor intensity is reduced.

Detailed Description

The present invention will now be described for a clearer understanding of technical features, objects, and effects of the present invention.

The principle of the invention is as follows: the microalloy such as Nb, V, ti and the like can improve the strength performance of the steel bar in the modes of solid solution strengthening, fine grain strengthening, precipitation strengthening and the like, so that the consumption of the microalloy such as Nb, V, ti and the like is reduced, the strength of the steel bar can be obviously reduced, and the GB/T1499.2-2018 part 2 of steel for reinforced concrete can still be met for ensuring the strength of the steel bar: the requirement of hot rolled ribbed bars requires that the strength of the bars be increased by other means. Wherein, the crystal grains can be obviously refined by the controlled rolling and cooling technology, and the strength of the steel bar is greatly improved.

And (3) component design: the chemical components of the common bar (hereinafter referred to as common bar) are as follows in percentage by weight: 0.21 to 0.25 percent, si:0.40 to 0.70 percent, mn:1.10 to 1.30 percent, P is less than or equal to 0.045 percent, S is less than or equal to 0.045 percent, and the balance is Fe;

1. the invention sets the initial rolling temperature of the double high bars to 950-1000 ℃, can prevent the growth of crystal grains in the heating process and refines austenite crystal grains. In order to prevent the crystal grain growth caused by temperature rise in the rolling process, the 2 water tanks before entering the finishing mill are all opened with 40-80% of water, the two high bars are controlled to enter the finishing mill at 900-930 ℃, the 2 water tanks before entering the reducing mill are all opened with 20-50% of water, the entering reducing mill is controlled to be 830-870 ℃ and the cooling bed is naturally cooled. In addition, the water tank and the recovery section after reducing are not arranged, or the water tank and the recovery section after reducing are arranged, but when the steel bar passes through the water tank and the recovery section after reducing, the water in the water tank after reducing is not opened, so that water penetration or forced cooling is avoided. Because the water passing through the water is cooled and boiled, the cooling strength is high, and the surface of the steel bar is provided with tempered sorbite tissues. According to the invention, through temperature control in the rolling process, especially weak cooling control after rolling, the surface of the steel bar is only ferrite and pearlite, and no tempered sorbite structure or martensitic structure exists.

2. The double high bar process (two-split) is: blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, billet continuous casting, heating by a heating furnace, rough rolling, middle rolling, a water tank and a recovery section, finish rolling, a water tank and a recovery section, reducing a diameter, cutting multiple lengths, cooling, cutting fixed lengths, collecting, bundling, weighing, listing and warehousing.

3. After BOF blowing, adopting a sliding plate to stop slag and discharge steel, then adding alloy and deoxidizer to ensure that the content of C is 0.21-0.25%, the content of Si is 0.40-0.70%, the content of Mn is 1.10-1.30%, and the content of P, S is less than or equal to 0.045%, then sending the molten iron to an argon station to blow argon, adopting proper secondary cooling parameters for continuous casting, and adopting a whole-course protection casting process to cast;

4. the square billet cast by continuous casting is heated by a heating furnace, the temperature of a first heating section is controlled to be 1000-1060 ℃, the temperature of a second heating section is controlled to be 1060-1120 ℃, the temperature of a soaking section is controlled to be 1040-1100 ℃, the initial rolling temperature is controlled to be 950-1000 ℃, after rough rolling and intermediate rolling, the temperature of finish rolling is controlled to be 900-930 ℃, the temperature of reducing diameter is controlled to be 830-870 ℃, and the square billet is naturally cooled by a cooling bed.

Table 1: composition of the example steels

Examples	Production line	Specification of specification	C	Si	Mn	P	S
								Example 1	Double high rod	Φ10	0.22	0.48	1.18	0.027	0.031
Example 2	Double high rod	Φ12	0.22	0.50	1.19	0.030	0.025
								Example 3	Double high rod	Φ14	0.23	0.45	1.18	0.041	0.026
Example 4	Double high rod	Φ16	0.23	0.47	1.20	0.031	0.021
								Example 5	Double high rod	Φ18	0.22	0.45	1.19	0.020	0.022
Example 6	Double high rod	Φ20	0.22	0.44	1.18	0.029	0.020

Table 2: heating process of steel of each embodiment

Examples	Production line	Specification of specification	Temperature of furnace charging	A heating temperature	Two heating temperatures	Soaking temperature	Heating time
								Example 1	Double high rod	Φ10	682	1012	1097	1059	82
Example 2	Double high rod	Φ12	633	1027	1079	1062	80
								Example 3	Double high rod	Φ14	642	1029	1085	1058	79
Example 4	Double high rod	Φ16	695	1018	1096	1049	75
								Example 5	Double high rod	Φ18	701	1023	1076	1048	78
Example 6	Double high rod	Φ20	642	1019	1092	1066	81

Table 3: rolling technology of steel of each embodiment of bar

Examples	Production line	Segmentation	Specification of specification	Start rolling temperature	Temperature of finish rolling	Reducing temperature of inlet and outlet
							Example 1	Double high rod	2	Φ10	971	915	845
Example 2	Double high rod	2	Φ12	975	903	851
							Example 3	Double high rod	2	Φ14	984	919	835
Example 4	Double high rod	2	Φ16	983	913	838
							Example 5	Double high rod	2	Φ18	973	911	833
Example 6	Double high rod	2	Φ20	990	916	839

Table 4: mechanical Properties of the steels of the examples

Examples	Production line	Specification of specification	Yield strength Mpa	Tensile strength Mpa	A(％)	Agt(％)	Ratio of strong to bending
								Example 1	Double high rod	Φ10	460	630	31	17.6	1.37
Example 2	Double high rod	Φ12	455	620	29	14.5	1.36
								Example 3	Double high rod	Φ14	455	620	27	14.2	1.36
Example 4	Double high rod	Φ16	445	615	28	15.3	1.38
								Example 5	Double high rod	Φ18	450	610	28	13.9	1.36
Example 6	Double high rod	Φ20	455	610	29	14.6	1.34

A is elongation after breaking, unit, agt is maximum force total elongation, unit: % of (B)

Table 5: metallographic structure of the steels of each example

Examples

Production line

Specification of specification

Macroscopic tissue

Superficial tissue

1/4 of the tissue

Grain size at 1/4

P content at 1/4 position

Center organization

Example 1

Double high rod

Φ10

No loop

P+F

11.5

39％

P+F

Example 2

Double high rod

Φ12

No loop

P+F

11.5

34％

P+F

Example 3

Double high rod

Φ14

No loop

P+F

11.5

36％

P+F

Example 4

Double high rod

Φ16

No loop

P+F

11.0

41％

P+F

Example 5

Double high rod

Φ18

No loop

P+F

11.0

38％

P+F

Example 6

Double high rod

Φ20

No loop

P+F

11.0

35％

P+F

The embodiment 1-6 shows that the invention can reduce the use amount of Nb, V, ti and other micro alloys by adopting a proper rolling process through reasonable chemical composition control, reduce the alloy cost of ton steel to 65 yuan, simultaneously reduce the manual input alloy amount of a converter, reduce the labor intensity, and simultaneously ensure that the steel bar has better mechanical property and the metallographic structure meets the requirements of GB/T1499.2-2018.

The foregoing is illustrative of the present invention and is not to be construed as limiting the scope of the invention. In order that the components of the invention may be combined without conflict, any person skilled in the art shall make equivalent changes and modifications without departing from the spirit and principles of the invention.

Claims

1. The hot rolled ribbed steel bar produced by the double high bars is characterized by comprising the following components in percentage by weight: 0.21 to 0.25 percent, si:0.40 to 0.70 percent, mn:1.10 to 1.30 percent, P is less than or equal to 0.045 percent, S is less than or equal to 0.045 percent, and the balance is Fe;

the specification of the hot rolled ribbed steel bar is phi 10-phi 20mm, and two-splitting rolling is adopted;

the yield strength of the hot rolled ribbed steel bar is more than or equal to 440Mpa, the tensile strength is more than or equal to 600Mpa, the elongation after fracture A is more than or equal to 25%, the maximum total elongation Agt is more than or equal to 13%, and the strength-to-deflection ratio is more than or equal to 1.33;

the hot rolled ribbed steel bar has a metallographic structure of: macroscopic organization: no loop; surface layer tissue: pearlite + ferrite; 1/4 tissue: pearlite + ferrite; grain size at 1/4: 11.0-12 stages; the pearlite content at 1/4 position is 34% -41%; center organization: pearlite + ferrite.

2. The hot rolled ribbed steel bar produced by double high bar as in claim 1 wherein the method of producing the hot rolled ribbed steel bar produced by double high bar comprises: the production method adopts two-segmentation and high-speed bar rolling; the production method comprises the following steps: blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, billet continuous casting, heating by a heating furnace, rough rolling, middle rolling, a front finish rolling water tank and a recovery section, finish rolling, a front reducing water tank and a recovery section, reducing, shearing multiple length, cooling bed, shearing fixed length, collecting and bundling;

3. The hot rolled ribbed bar produced by twin high rod as claimed in claim 1, wherein the finished gauge is phi 10mm and the rolling speed is 40m/s.

4. The hot rolled ribbed bar produced by twin high rod as claimed in claim 1, wherein the finished gauge is phi 12mm and the rolling speed is 36m/s.

5. The hot rolled ribbed bar produced from dual high bar according to claim 1, characterized in that the finished gauge is phi 14mm, the rolling speed is 27m/s.

6. The hot rolled ribbed bar produced by twin high rod as claimed in claim 1, wherein the finished gauge is phi 16mm and the rolling speed is 23m/s.

7. The hot rolled ribbed bar of claim 1 wherein the finished gauge is 18mm and the rolling speed is 16m/s.

8. The hot rolled ribbed bar produced by twin high rod as claimed in claim 1, wherein the finished gauge is phi 20mm and the rolling speed is 15m/s.

9. The hot rolled ribbed steel bar produced from double high bars of claim 1 wherein the hot rolled ribbed steel bar comprises the following components: c:0.22% >, si:0.48%, mn:1.18%, P:0.027%, S:0.031% and the balance of Fe.

10. The hot rolled ribbed bar produced from double high bar as in claim 1 wherein C:0.23%, si:0.45%, mn:1.18%, P:0.041%, S:0.026% and the balance of Fe.