WO2020228232A1

WO2020228232A1 - Tmcp-type high-performance bridge steel plate with a yield of 370 mpa and manufacturing method therefor

Info

Publication number: WO2020228232A1
Application number: PCT/CN2019/110795
Authority: WO
Inventors: 李伟; 洪君; 丁叶
Original assignee: 南京钢铁股份有限公司
Priority date: 2019-05-14
Filing date: 2019-10-12
Publication date: 2020-11-19
Also published as: CN110106441A

Abstract

Disclosed is a TMCP-type high-performance bridge steel plate with a yield of 370 MPa, which relates to the technical field of iron and steel smelting. The bridge steel plate has the following chemical ingredients in mass percentages: C: 0.08%-0.14%, Si: 0.20%-0.30%, Mn: 1.35%-1.50%, P ≤ 0.015%, S ≤ 0.005%, Ni ≤ 0.18%, Cr ≤ 0.18%, Nb: 0.020%-0.035%, Alt: 0.025%-0.050%, Ti: 0.008%-0.020%, the balance being Fe and other inevitable impurities. By optimizing the ingredient design, a high-performance Q370 bridge steel with excellent mechanical and welding properties is developed, which shortens a process flow, and also reduces the cost of alloys.

Description

TMCP type yielding 370MPa high performance bridge steel plate and production method

Technical field

The invention relates to the technical field of steel smelting, in particular to a TMCP type high-performance bridge steel plate with a yield of 370 MPa and a production method.

Background technique

The safety, reliability and durability of key bridge structures put forward clear requirements for the development of high-performance bridge steels that integrate multiple indicators such as high strength, high toughness, low yield ratio, and easy welding. Q370 bridge steel is currently the most widely used and the largest amount of bridge steel in large-span steel bridges in my country. However, Q370 bridge steel plates are delivered in a normalized state. Bridge factories report that there are high carbon content and carbon equivalent, and joint impact With low power and other issues, steel plants will also have problems with greater production difficulty and higher production costs.

Summary of the invention

In order to solve the above technical problems, the present invention provides a TMCP-type high-performance bridge steel plate with a yield of 370MPa. The chemical composition and mass percentage are as follows: C: 0.08%～0.14%, Si: 0.20%～0.30%, Mn: 1.35%～1.50 %, P≤0.015%, S≤0.005%, Ni≤0.18%, Cr≤0.18%, Nb: 0.020%～0.035%, Alt: 0.025%～0.050%, Ti: 0.008%～0.020%, the balance is Fe And inevitable impurities.

Technical effect: The present invention optimizes the composition design, adopts low-carbon, micro-Nb, low-carbon equivalent composition design and TMCP production process, and gives full play to the two effects of Nb on ferrite grain refinement and precipitation strengthening during the controlled rolling and controlled cooling process. In this respect, the research and development of high-performance Q370 bridge steel with excellent mechanical properties and welding properties shortens the process flow and reduces alloy costs.

The technical solution further limited by the present invention is:

For the aforementioned TMCP type high-performance bridge steel plate with a yield of 370MPa, the maximum thickness of the finished steel plate is 80mm, and when the thickness H is 10≤H≤50mm, Ni:0%, Cr:0%; when the thickness H is 50＜H≤80mm , Ni: 0.10%～0.18%, Cr: 0.10%～0.18%.

Another object of the present invention is to provide a TMCP type yielding 370MPa high-performance bridge steel plate production method, including smelting, continuous casting, heating, controlled rolling and controlled cooling processes,

The smelting and continuous casting processes specifically include molten iron desulfurization pretreatment, converter smelting, LF refining, RH vacuum treatment and continuous casting. After molten iron desulfurization pretreatment, S≤0.003%, converter smelting adopts double slag method to control P≤0.012%, LF refining White slag is used for desulfurization and deoxidation, the vacuum degree is 5.0mbar and the vacuum time is more than 12 minutes during RH vacuum treatment, calcium treatment is carried out after the vacuum is over, and the calcium treatment is statically stirred for more than 10 minutes;

The heating process adopts 150-260mm thick continuous casting billet, the total furnace time is calculated at 8-16min/cm, the soaking time is calculated at 1.4min/cm or more, and the tapping temperature is 1160-1230℃;

The controlled rolling and controlled cooling process adopts a two-stage controlled rolling process of austenite recrystallized zone + unrecrystallized zone for rolling. The final rolling temperature of the rough rolling in the first stage is controlled to 1000～1100℃, and the start rolling temperature of the second stage is 840～ 920℃, the final rolling temperature is 780～860℃, after rolling, DQ ultra-fast cooling is used for rapid cooling, the cooling rate is 3～5℃/s, and the redness temperature is 540～660℃.

The aforementioned TMCP type yielding 370MPa high-performance bridge steel plate production method, the thickness of the finished steel plate is 16mm, and its chemical composition and mass percentage are as follows: The thickness of the finished steel plate is 16mm, and its chemical composition and mass percentage are as follows: C: 0.09%～0.11% , Si: 0.2%～0.3%, Mn: 1.43%～1.50%, P≤0.015%, S≤0.005%, Ti: 0.01%～0.02%, Nb: 0.025%～0.035%, Alt: 0.028%～0.038% , Ceq: 0.35%～0.38%, the balance is Fe and other inevitable impurities;

Steelmaking process: molten steel undergoes desulfurization pretreatment, converter smelting, LF refining, RH vacuum treatment, and then continuous casting into a 260mm thick continuous casting billet. After molten iron desulfurization pretreatment, S≤0.003% is controlled. Converter smelting adopts double slag method Control P≤0.012%, LF refining adopts white slag operation for desulfurization and deoxidation. During RH vacuum treatment, the vacuum is 5.0mbar and the vacuum time is more than 12 minutes. After the vacuum is completed, the calcium treatment is carried out, and the calcium treatment is completed and statically stirred for more than 10 minutes;

The total heating time of the continuous casting billet is 274min, the soaking time is 66min, and the tapping temperature is 1194℃; the two-stage controlled rolling technology of austenite recrystallized zone and austenite non-recrystallized zone is adopted, the first stage The rough rolling opening temperature is 1080°C, the second stage finishing rolling opening temperature is 935°C, and the final rolling temperature is 814°C. After finishing rolling, ultra-fast cooling and rapid cooling are carried out, the cooling rate is 3°C/s, and the redness temperature is 654°C. .

The aforementioned TMCP type yielding 370MPa high-performance bridge steel plate production method, the thickness of the finished steel plate is 48mm, and its chemical composition and mass percentage are as follows: the thickness of the finished steel plate is 48mm, and its chemical composition and mass percentage are as follows: C: 0.12%～0.14% , Si: 0.2%～0.3%, Mn: 1.35%～1.45%, P≤0.015%, S≤0.005%, Ti: 0.01%～0.02%, Nb: 0.025%～0.035%, Alt: 0.032%～0.042% , Ceq: 0.35%～0.38%, the balance is Fe and other inevitable impurities;

The molten steel undergoes desulfurization pretreatment, converter smelting, LF refining, RH vacuum treatment, and then continuous casting is cast into a 260mm thick continuous casting billet. After the molten iron desulfurization pretreatment, the control S≤0.003%, the converter smelting adopts the double slag method to control P≤0.012 %, LF refining adopts white slag operation for desulfurization and deoxidation. During RH vacuum treatment, the vacuum degree is 5.0 mbar and the vacuum time is more than 12 minutes. After the vacuum is completed, the calcium treatment is performed, and the calcium treatment is completed and statically stirred for more than 10 minutes;

The total heating time of the continuous casting billet is 269min, the soaking time is 44min, and the tapping temperature is 1172℃; the two-stage controlled rolling technology of austenite recrystallization zone and austenite non-recrystallization zone is adopted, the first stage The rough rolling opening temperature is 1072℃, the second stage finishing rolling opening temperature is 865℃, and the final rolling temperature is 807℃. After finishing rolling, ultra-rapid cooling is carried out. The cooling rate is 4℃/s and the redness temperature is 634℃. .

The aforementioned TMCP yielding 370MPa high-performance bridge steel plate production method, the thickness of the finished steel plate is 80mm, and its chemical composition and mass percentage are as follows: the thickness of the finished steel plate is 80mm, and its chemical composition and mass percentage are as follows: C: 0.08%～0.10% , Si: 0.2%～0.3%, Mn: 1.4%～1.5%, P≤0.015%, S≤0.005%, Ti: 0.008%～0.018%, Nb: 0.02%～0.03%, Alt: 0.03%～0.04% , Ni: 0.10%～0.18%, Cr: 0.10%～0.18%, Ceq: 0.35%～0.38%, the balance is Fe and other unavoidable impurities;

The total heating time of the continuous casting billet is 274min, the soaking time is 66min, and the tapping temperature is 1194℃; the two-stage controlled rolling technology of austenite recrystallized zone and austenite non-recrystallized zone is adopted, the first stage The rough rolling opening temperature is 1060℃, the second stage finishing rolling opening temperature is 931℃, and the final rolling temperature is 809℃. After finishing rolling, ultra-fast cooling and rapid cooling are carried out, the cooling rate is 5℃/s, and the redness temperature is 570℃ .

The beneficial effects of the present invention are:

(1) The present invention produces 370MPa high-performance bridge steel plates with a thickness of 10 to 80mm, adopts TMCP production process, and produces steel plates with high strength, yield strength not less than 370MPa, and excellent low-temperature toughness and plasticity results;

(2) The chemical composition design principle adopted in the present invention is: C and Mn elements play the role of solid solution strengthening; the thin plate is strengthened by micro-Nb alloy fine-grained, and the thick plate is added with appropriate amounts of Cr, Ni and other fine-grained elements. Low-C, micro-Nb, Ti alloy composition design, 50mm thick steel plate supplemented with Ni, Cr and other alloy elements to ensure the strength of the steel plate and low-temperature impact toughness; through reasonable heating, controlled rolling and controlled cooling processes, the steel plate has a good integration Mechanical properties

(3) The delivery method of the steel plate of the present invention is TMCP, and the TMCP state structure is mainly ferrite + pearlite, no heat treatment is required, and process cost can be saved;

(4) The present invention optimizes the composition design, Ceq is 0.35～0.38%, controls the smelting and continuous casting processes, and carries out appropriate heating and controlled rolling and cooling processes. The final steel plate has good mechanical properties, and the yield strength is 400～ 480MPa, tensile strength between 520～600MPa, elongation ＞21%, yield ratio ≤0.83, 1/4 plate thickness -20℃ longitudinal impact energy ≥200J, product meets GB/T714-2015 "Structural steel for bridges" "standard.

Description of the drawings

Fig. 1 is a morphology diagram of the 1/4 thickness of the steel plate in Example 1 of the present invention;

Fig. 2 is a morphology diagram of the 1/4 thickness of the steel plate in Example 2 of the present invention;

Figure 3 is a morphology diagram of the 1/4 thickness of the steel plate in Example 3 of the present invention.

Detailed ways

Example 1

This embodiment provides a TMCP type high-performance bridge steel plate with a yield of 370MPa. The finished steel plate has a thickness of 16mm, and its chemical composition and mass percentage are as follows: C: 0.09%～0.11%, Si: 0.2%～0.3%, Mn: 1.43% ～1.50%, P≤0.015%, S≤0.005%, Ti: 0.01%～0.02%, Nb: 0.025%～0.035%, Alt: 0.028%～0.038%, Ceq: 0.35%～0.38%, the balance is Fe And other inevitable impurities.

The mechanical properties of the obtained steel plate are: the yield ratio is 0.82, the yield strength is 459MPa, the tensile strength is 560MPa, the elongation is 24.7%, and the average longitudinal impact energy of 1/4 plate thickness at -20°C is 236J.

Example 2

This embodiment provides a TMCP type high-performance bridge steel plate with a yield of 370 MPa. The finished steel plate has a thickness of 48 mm, and its chemical composition and mass percentage are as follows: C: 0.12% to 0.14%, Si: 0.2% to 0.3%, Mn: 1.35% ～1.45%, P≤0.015%, S≤0.005%, Ti: 0.01%～0.02%, Nb: 0.025%～0.035%, Alt: 0.032%～0.042%, Ceq: 0.35%～0.38%, the balance is Fe And other inevitable impurities.

The mechanical properties of the obtained steel plate are: the yield ratio is 0.80, the yield strength is 433MPa, the tensile strength is 541MPa, the elongation is 23.2%, and the average longitudinal impact energy of 1/4 plate thickness at -20°C is 235J.

Example 3

This embodiment provides a TMCP-type high-performance bridge steel plate with a yield of 370 MPa. The finished steel plate has a thickness of 80mm, and its chemical composition and mass percentage are as follows: C: 0.08%～0.10%, Si: 0.2%～0.3%, Mn: 1.4% ～1.5%, P≤0.015%, S≤0.005%, Ti: 0.008%～0.018%, Nb: 0.02%～0.03%, Alt: 0.03%～0.04%, Ni: 0.10%～0.18%, Cr: 0.10% ~0.18%, Ceq: 0.35%~0.38%, the balance is Fe and other unavoidable impurities.

The mechanical properties of the obtained steel plate are: the yield ratio is 0.77, the yield strength is 410 MPa, the tensile strength is 532 MPa, the elongation is 22.7%, and the average longitudinal impact energy of 1/4 plate thickness at -20°C is 232J.

The mechanical properties of the steel plate obtained in the present invention all meet the performance requirements of Q370qD in the GB/T 714-2015 "Steel for Bridge Structures" standard, and the mechanical properties are excellent and have strong operability.

The annual output of TMCP 370MPa high-performance bridge steel plates below 80mm is about 1.7 tons, and the profit per ton of steel is about 300 yuan/ton. The annual benefit is about 300 yuan/ton×17,000 tons=5.1 million yuan.

In addition to the foregoing embodiments, the present invention may also have other embodiments. All technical solutions formed by equivalent replacements or equivalent transformations fall within the protection scope of the present invention.

Claims

A TMCP type high-performance bridge steel plate with a yield of 370MPa, characterized in that its chemical composition and mass percentage are as follows: C: 0.08%～0.14%, Si: 0.20%～0.30%, Mn: 1.35%～1.50%, P≤0.015 %, S≤0.005%, Ni≤0.18%, Cr≤0.18%, Nb: 0.020%～0.035%, Alt: 0.025%～0.050%, Ti: 0.008%～0.020%, the balance is Fe and inevitable impurities .
The TMCP type high-performance bridge steel plate with a yield of 370MPa according to claim 1, wherein the maximum thickness of the finished steel plate is 80mm, and when the thickness H is 10≤H≤50mm, Ni:0%, Cr:0%; thickness H When 50<H≤80mm, Ni: 0.10% to 0.18%, Cr: 0.10% to 0.18%.
A TMCP type yielding 370MPa high-performance bridge steel plate production method is characterized by including smelting, continuous casting, heating, controlled rolling and controlled cooling processes,

The smelting and continuous casting processes specifically include molten iron desulfurization pretreatment, converter smelting, LF refining, RH vacuum treatment and continuous casting. After molten iron desulfurization pretreatment, S≤0.003%, converter smelting adopts double slag method to control P≤0.012%, LF refining White slag is used for desulfurization and deoxidation, the vacuum degree is 5.0mbar and the vacuum time is more than 12 minutes during RH vacuum treatment, calcium treatment is carried out after the vacuum is over, and the calcium treatment is statically stirred for more than 10 minutes;

The heating process adopts 150-260mm thick continuous casting billet, the total furnace time is calculated at 8-16min/cm, the soaking time is calculated at 1.4min/cm or more, and the tapping temperature is 1160-1230℃;

The controlled rolling and controlled cooling process adopts a two-stage controlled rolling process of austenite recrystallized zone + unrecrystallized zone for rolling. The final rolling temperature of the rough rolling in the first stage is controlled to 1000～1100℃, and the start rolling temperature of the second stage is 840～ 920℃, the final rolling temperature is 780～860℃, after rolling, DQ ultra-fast cooling is used for rapid cooling, the cooling rate is 3～5℃/s, and the redness temperature is 540～660℃.
The method for producing TMCP high-performance bridge steel plate with a yield of 370 MPa according to claim 3, characterized in that: the thickness of the finished steel plate is 16mm, and its chemical composition and mass percentage are as follows: C: 0.09%～0.11%, Si: 0.2%～0.3 %, Mn: 1.43%～1.50%, P≤0.015%, S≤0.005%, Ti: 0.01%～0.02%, Nb: 0.025%～0.035%, Alt: 0.028%～0.038%, Ceq: 0.35%～0.38 %, the balance is Fe and other unavoidable impurities;

Steelmaking process: molten steel undergoes desulfurization pretreatment, converter smelting, LF refining, RH vacuum treatment, and then continuous casting into a 260mm thick continuous casting billet. After molten iron desulfurization pretreatment, S≤0.003% is controlled. Converter smelting adopts double slag method Control P≤0.012%, LF refining adopts white slag operation for desulfurization and deoxidation. During RH vacuum treatment, the vacuum is 5.0mbar and the vacuum time is more than 12 minutes. After the vacuum is completed, the calcium treatment is carried out, and the calcium treatment is completed and statically stirred for more than 10 minutes;

The total heating time of the continuous casting billet is 274min, the soaking time is 66min, and the tapping temperature is 1194℃; the two-stage controlled rolling technology of austenite recrystallized zone and austenite non-recrystallized zone is adopted, the first stage The rough rolling opening temperature is 1080°C, the second stage finishing rolling opening temperature is 935°C, and the final rolling temperature is 814°C. After finishing rolling, ultra-fast cooling and rapid cooling are carried out, the cooling rate is 3°C/s, and the redness temperature is 654°C. .
The TMCP type yielding 370MPa high-performance bridge steel plate production method according to claim 3, characterized in that the thickness of the finished steel plate is 48mm, and its chemical composition and mass percentage are as follows: C: 0.12% to 0.14%, Si: 0.2% to 0.3 %, Mn: 1.35%～1.45%, P≤0.015%, S≤0.005%, Ti: 0.01%～0.02%, Nb: 0.025%～0.035%, Alt: 0.032%～0.042%, Ceq: 0.35%～0.38 %, the balance is Fe and other unavoidable impurities;

The molten steel undergoes desulfurization pretreatment, converter smelting, LF refining, RH vacuum treatment, and then continuous casting is cast into a 260mm thick continuous casting billet. After the molten iron desulfurization pretreatment, the control S≤0.003%, the converter smelting adopts the double slag method to control P≤0.012 %, LF refining adopts white slag operation for desulfurization and deoxidation. During RH vacuum treatment, the vacuum degree is 5.0 mbar and the vacuum time is more than 12 minutes. After the vacuum is completed, the calcium treatment is performed, and the calcium treatment is completed and statically stirred for more than 10 minutes;

The total heating time of the continuous casting billet is 269min, the soaking time is 44min, and the tapping temperature is 1172℃; the two-stage controlled rolling technology of austenite recrystallization zone and austenite non-recrystallization zone is adopted, the first stage The rough rolling opening temperature is 1072℃, the second stage finishing rolling opening temperature is 865℃, and the final rolling temperature is 807℃. After finishing rolling, ultra-rapid cooling is carried out. The cooling rate is 4℃/s and the redness temperature is 634℃. .
The TMCP type yielding 370MPa high-performance bridge steel plate production method according to claim 3, characterized in that the thickness of the finished steel plate is 80mm, and its chemical composition and mass percentage are as follows: C: 0.08%～0.10%, Si: 0.2%～0.3 %, Mn: 1.4%～1.5%, P≤0.015%, S≤0.005%, Ti: 0.008%～0.018%, Nb: 0.02%～0.03%, Alt: 0.03%～0.04%, Ni: 0.10%～0.18 %, Cr: 0.10%～0.18%, Ceq: 0.35%～0.38%, the balance is Fe and other inevitable impurities;

The molten steel undergoes desulfurization pretreatment, converter smelting, LF refining, RH vacuum treatment, and then continuous casting is cast into a 260mm thick continuous casting billet. After the molten iron desulfurization pretreatment, the control S≤0.003%, the converter smelting adopts the double slag method to control P≤0.012 %, LF refining adopts white slag operation for desulfurization and deoxidation. During RH vacuum treatment, the vacuum degree is 5.0 mbar and the vacuum time is more than 12 minutes. After the vacuum is completed, the calcium treatment is performed, and the calcium treatment is completed and statically stirred for more than 10 minutes;

The total heating time of the continuous casting billet is 274min, the soaking time is 66min, and the tapping temperature is 1194℃; the two-stage controlled rolling technology of austenite recrystallized zone and austenite non-recrystallized zone is adopted, the first stage The rough rolling opening temperature is 1060℃, the second stage finishing rolling opening temperature is 931℃, and the final rolling temperature is 809℃. After finishing rolling, ultra-fast cooling and rapid cooling are carried out, the cooling rate is 5℃/s, and the redness temperature is 570℃ .