CN111944952A - Smelting and rolling process for hot-rolled coil plate of titanium microalloy pipeline steel - Google Patents

Smelting and rolling process for hot-rolled coil plate of titanium microalloy pipeline steel Download PDF

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Publication number
CN111944952A
CN111944952A CN202010823610.7A CN202010823610A CN111944952A CN 111944952 A CN111944952 A CN 111944952A CN 202010823610 A CN202010823610 A CN 202010823610A CN 111944952 A CN111944952 A CN 111944952A
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steel
rolling
percent
hot
titanium
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高振伟
李延芝
李君彦
李世伟
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Wuan Yuhua Iron And Steel Co ltd
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Wuan Yuhua Iron And Steel Co ltd
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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/06Deoxidising, e.g. killing
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006Adding metallic additives
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0056Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/064Dephosphorising; Desulfurising
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/072Treatment with gases

Abstract

The invention belongs to the technical field of steel processing, and provides a rolling process for a hot-rolled coil plate of titanium microalloy pipeline steel, which comprises the following steps: the method comprises the following steps of molten iron pretreatment, top and bottom combined blown converter, LF refining, slab continuous casting, hot continuous rolling mill steel rolling, laminar cooling and coiling, wherein the LF refining: the deoxidizer comprises the following components in percentage by mass: 10 to 30 percent of Al and 5 to 20 percent of CaC21 to 5 percent of Ti, 0.1 to 2.0 percent of bentonite and 3.21 to 6.03 percent of SiO20.58 to 1.32 percent of FeO, 0.39 to 1.01 percent of MnO, 21.56 to 35.96 percent of CaO, 18.19 to 26.05 percent of Al2O33.47 to 6.32 percent of MgO. By the technical scheme, the titanium microalloy tube in the prior art is solvedLow hardenability, poor low-temperature toughness and high inclusion content of wire-line steel.

Description

Smelting and rolling process for hot-rolled coil plate of titanium microalloy pipeline steel
Technical Field
The invention belongs to the technical field of steel processing, and relates to a rolling process for a hot-rolled coil plate of titanium microalloy pipeline steel.
Background
With the development of domestic economy, the situation of saving resources and reducing emission is increasingly severe, and users have thinner and thinner requirements on the thickness of products, which means that steel products have ultrahigh strength and toughness and good forming performance so as to achieve the aim of not influencing the use safety of the products after the thickness of the products is reduced. The microalloying can effectively improve the comprehensive mechanical property of steel materials, and the grain size is controlled by adding elements such as Ti, Nb, V and the like into steel, and nano-scale carbide is precipitated, thus playing roles of precipitation strengthening and fine grain strengthening.
The microalloying elements comprise titanium, vanadium, niobium, boron, aluminum, zirconium, tantalum and the like, and the microalloying elements and carbon, nitrogen, oxygen, sulfur and other elements in the steel can form various compounds, so that the properties of the steel are influenced. Microalloying of steel is now being used in a wider variety of fields such as medium carbon non-heat treated steels, steel reinforcements, high carbon rail steels, heat resistant tool steels, stainless steels, and the like. These steels can achieve good combined use performance of strength, toughness, formability and weldability at a relatively low cost. The currently available strength range of microalloyed steel is 400-600 MPa (yield strength), and the microalloyed steel is widely applied to various engineering structures such as bridges, buildings, ships, vehicles, pressure vessels, oil extraction platforms, oil pipelines and the like. Because the demand of the steel with the application generally accounts for about 60 percent of the total demand of the society for the steel, the microalloyed steel has wide application prospect and is a main product in the modern steel industry.
At present, the price of common ferrocolumbium and ferrovanadium in the market is more than 10 times higher than that of ferrotitanium, and the price of the common ferrocolumbium and ferrovanadium in the market tends to be increased continuously, and in recent years, low-carbon titanium-containing steel as low-alloy high-strength steel is rapidly developed at home and abroad and is gradually widely applied. Titanium is used for replacing other microalloy elements, which is one of the development directions of alloying and has wide application prospect, but the prior titanium microalloy steel has the problems of low hardenability of steel, poor low-temperature toughness and high inclusion content.
Disclosure of Invention
The invention provides a rolling process for a hot-rolled coil plate of titanium micro-alloy pipeline steel, which solves the problems of low hardenability, poor low-temperature toughness and high inclusion content of the titanium micro-alloy pipeline steel in the prior art.
The technical scheme of the invention is realized as follows:
a rolling process for a hot-rolled coiled plate of titanium microalloy pipeline steel comprises the following steps: the method comprises the following steps of molten iron pretreatment, top-bottom combined blowing converter, LF refining, slab continuous casting, hot continuous rolling mill steel rolling, laminar cooling and coiling, wherein the LF refining process comprises the following steps: adding a carburant, lime, a deoxidizer, a pure calcium wire, titanium, boron and selenium into the molten steel in sequence, and then blowing argon, calming a steel ladle and discharging slag to obtain refined molten steel;
the deoxidizer comprises the following components in percentage by mass: 10 to 30 percent of Al and 5 to 20 percent of CaC21 to 5 percent of Ti, 0.1 to 2.0 percent of bentonite and 3.21 to 6.03 percent of SiO20.58 to 1.32 percent of FeO, 0.39 to 1.01 percent of MnO, 21.56 to 35.96 percent of CaO, 18.19 to 26.05 percent of Al2O33.47 to 6.32 percent of MgO;
the refined molten steel comprises the following components in percentage by mass: 0.060% -0.080% of C, 0.800% -0.950% of Mn, 0.120% -0.200% of Si, 0.025% -0.045% of Al, less than or equal to 0.010% of S, less than or equal to 0.015% of P, less than or equal to 0.008% of N, 0.055% -0.060% of Ti, 0.015% -0.020% of B, 0.050% -0.100% of Se, and the balance of Fe and impurities.
As a further technical scheme, the mass percent of the deoxidizer components is as follows: CaC2≥Ti+MgO。
According to a further technical scheme, the molten iron pretreatment is to pour molten iron into a ladle, slag before skimming is carried out for 5-8 min, 4.5-8 kg of desulfurizing agent is added into each ton of molten iron, stirring is carried out for 8-15 min, and after stirring is stopped, slag after skimming is carried out for 6-8 min, so that pretreated molten iron is obtained.
As a further technical scheme, the molten iron comprises the following components in percentage by mass: c content is 4.2-5.1%, Mn content is 0.2-0.5%, S content is less than or equal to 0.03%, P content is less than or equal to 0.130%, and Si content is 0.25-0.55%; the temperature of the molten iron is equal to or more than 1280 ℃, and the slag carrying amount of the molten iron is equal to or less than 2 cm.
As a further technical scheme, the top furnace combined blowing converter is used for conveying pretreated molten iron into the converter, then adding scrap steel into the converter for blowing to obtain molten steel, wherein the temperature of the molten steel is more than or equal to 1640 ℃.
As a further technical scheme, the argon blowing in the LF refining is to install an air supply element at the bottom of a steel ladle, and the argon is blown into molten steel through a pipeline through the bottom air supply element;
the ladle is calmed, namely the ladle is hung on a continuous casting ladle turret to wait for casting after argon blowing is finished, and the waiting time is less than or equal to 10 min;
and in the slag discharging step, after the steel ladle is killed, molten steel in the steel ladle flows into a tundish, and steel slag is discharged through a back slag discharging port at the back of the tundish.
As a further technical scheme, the slab continuous casting is to inject refined molten steel obtained after LF refining into a tundish, and the refined molten steel flows into a crystallizer through the tundish to be continuously cast to obtain a continuous casting blank;
the temperature of the tundish is 1530-1550 ℃, and the pulling speed of the crystallizer is 1-1.5 m/min.
According to the further technical scheme, the hot continuous rolling mill is used for rolling steel, a continuous casting slab is heated at 1260 ℃, the heating time is more than or equal to 150min, the heated continuous casting slab is subjected to rough rolling to obtain an intermediate slab, and the intermediate slab is subjected to finish rolling to obtain a 15-20 mm steel plate.
As a further technical scheme, the rolling speed of finish rolling is 2.5-3.0 m/s, and the finishing temperature is controlled at 820-850 ℃.
According to a further technical scheme, the coiling is to coil a finish-rolled steel plate which is cooled to 590-620 ℃ by laminar flow.
The working principle and the beneficial effects of the invention are as follows:
1. according to the invention, through reasonable proportioning design of the components of the deoxidizer, the deoxidizer and a specific titanium microalloy pipeline steel hot-rolled coil rolling process work together to ensure that the hardenability J46/49-10 of the titanium microalloy pipeline steel hot-rolled coil is more than or equal to 528MPa, the yield strength is 506-528 MPa, the tensile strength is 603-630 MPa, the impact work is 216-222J at-30 ℃, B-type inclusions are not generated, and D-type inclusions are controlled at 0.5-1 level, so that the problems of low hardenability, poor low-temperature toughness and high inclusion content of titanium microalloy pipeline steel in the prior art are solved.
2. In the invention, the deoxidizer adopts 10-30% of Al and 5-20% of CaC as the components2、1%~5 percent of Ti, 0.1 to 2 percent of bentonite and 3.21 to 6.03 percent of SiO20.58 to 1.32 percent of FeO, 0.39 to 1.01 percent of MnO, 21.56 to 35.96 percent of CaO, 18.19 to 26.05 percent of Al2O33.47 to 6.32 percent of MgO, and the yield strength and the tensile strength of the titanium microalloy pipeline steel hot-rolled coil are improved, wherein the yield strength is 506 to 528MPa, and the tensile strength is 603 to 637 MPa.
Meanwhile, the mass percentage of the used components in the LF refining process conforms to that of CaC2The deoxidizer with the condition of more than or equal to Ti and MgO effectively reduces the inclusion content of the titanium micro-alloy pipeline steel, the prepared titanium micro-alloy pipeline steel hot-rolled coil has no B-type inclusions, and the generated D-type inclusions are controlled at 0.5 level; and the titanium micro-alloy pipeline steel hot-rolled coil plate prepared by using the deoxidizer which does not meet the condition or using medium-carbon ferromanganese and aluminum ingots to replace the deoxidizer can generate 0.5-grade B-type inclusions, and the D-type inclusions are 1-1.5-grade, so that the yield strength, the tensile strength and the low-temperature toughness are also reduced.
3. In the invention, when the refined molten steel meets the conditions of 0.060-0.080% of C, 0.800-0.950% of Mn, 0.120-0.200% of Si, 0.025-0.045% of Al, less than or equal to 0.010% of S, less than or equal to 0.015% of P, less than or equal to 0.008% of N, 0.055-0.060% of Ti, 0.015-0.020% of B, 0.050-0.100% of Se and the balance of Fe and impurities, the hardenability of the titanium steel prepared by refining the molten steel is not reduced due to the addition of Se element, and B, Se element generates a mutual synergistic enhancement effect and is matched with other components to further improve the yield strength and the tensile strength.
4. In the invention, the molten steel can be added with titanium after being fully deoxidized by the deoxidizer, and because the molten steel has high viscosity, the non-metal inclusions are not easy to separate and float upwards, so the key point of the steelmaking process is deep deoxidation at the back of a furnace, the deoxidizer is added in the tapping process, the steel ladle is fully stirred, the molten steel, the deoxidizer and the alloy are fully melted, the inclusions float upwards, and the inclusion content in the molten steel is reduced.
5. According to the invention, the C content in the refined molten steel is controlled to be 0.060-0.080%, so that the welding performance of the finally prepared titanium microalloy pipeline steel is improved; the content of S, P in the molten iron pretreatment procedure is reduced, the S content is controlled to be less than or equal to 0.010 percent, the P content is controlled to be less than or equal to 0.015 percent, and the content of inclusions in the finally prepared titanium steel is reduced; 0.055 to 0.060 percent of titanium is added to form TiN particles, and titanium nitride can be dissolved at higher temperature, so that the capability of preventing the grains from growing is stronger, which means that the titanium-containing steel can use higher heating temperature, and the higher the heating temperature is, more titanium carbide is dissolved, thereby leading to the subsequent precipitation strengthening, and the yield strength and the tensile strength of the finally prepared titanium micro-alloy pipeline steel are improved; in addition, in the steel rolling process, according to the precipitation characteristics of TiC and TiN, the temperature of a soaking section of the heating furnace is controlled to be 1260 ℃, and the heat preservation time is prolonged to be more than 150 min; the rolling speed of finish rolling is controlled and the finish rolling temperature is guaranteed to be 820-850 ℃, so that the aims of refining grains and reducing the precipitation of larger TiN particles are fulfilled; meanwhile, the coiling temperature is controlled at 590-620 ℃, and finally the low-temperature toughness of the titanium microalloy pipeline steel hot-rolled coil is improved.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the following examples 1 to 5 and comparative examples 1 to 7, blowing argon gas means that a gas supply element is installed at the bottom of a ladle, and argon gas is blown into molten steel through a pipeline through the bottom gas supply element;
the ladle calming means that the ladle is hung on a continuous casting ladle revolving platform for casting after argon blowing is finished, and the waiting time is less than or equal to 10 min;
slag discharge means that after the steel ladle is calmed, molten steel in the steel ladle flows into a tundish, and steel slag is discharged through a back slag discharge port at the back of the tundish;
the carburant is a steel-making carburant produced by Wuhan Pudong metallurgy materials Limited liability company;
the desulfurizer is an RH refining desulfurizer produced by Wuhan Xincheng chemical products Limited;
the waste steel is the waste steel produced when Yuhua steel plant produces SPHC type steel.
The compositions of the deoxidizers in examples 1 to 5 and comparative examples 1 to 7 are shown in Table 1, and the compositions of refined molten steel are shown in Table 2.
Example 1
A. Pouring molten iron into a ladle, wherein the temperature of the molten iron is 1280 ℃, the slag content of the molten iron is 2cm, and the molten iron comprises the following components in percentage by mass: 5.1% of C, 0.2% of Mn, 0.03% of S, 0.130% of P and 0.55% of Si; slagging off the pre-slag for 5min, inserting a stirring head into the molten iron below the liquid level by 1200mm, adding 8kg of desulfurizer into each ton of molten iron, stirring for 15min, lifting the stirring head to an upper limit after stopping stirring, and slagging off the pre-slag for 6min to obtain pretreated molten iron;
B. b, conveying the molten iron pretreated in the step A into a converter, adding scrap steel into the converter, and blowing to prepare molten steel, wherein the temperature of the molten steel is 1640 ℃; wherein the mass ratio of the scrap steel to the molten iron is 1: 4;
C. adding a carburant, lime, a deoxidizer, a pure calcium wire, titanium, boron and selenium into the molten steel in the step B in sequence, blowing argon, calming a steel ladle, and discharging slag to obtain refined molten steel;
D. pouring the refined molten steel obtained in the step C into a tundish, and flowing into a crystallizer through the tundish for continuous casting to obtain a continuous casting billet with the thickness of 200mm, wherein the temperature of the tundish is 1530 ℃, and the casting speed of the crystallizer is 1.5 m/min;
E. and D, heating the continuous casting slab in the step D by a heating furnace, wherein the soaking temperature is 1260 ℃, the total in-furnace time is 200min, roughly rolling the heated continuous casting slab to obtain an intermediate slab with the thickness of 35mm, finely rolling the intermediate slab by a 7-stand finishing mill group to obtain a steel plate, controlling the rolling speed at 3.0m/s, controlling the finish rolling temperature at 820 ℃, and finely rolling the steel plate to obtain the steel plate with the thickness of 20 mm.
F. And E, carrying out laminar cooling on the steel plate obtained after the finish rolling in the step E, cooling to 620 ℃, and then coiling to obtain the titanium micro-alloy pipeline steel hot-rolled coil.
Example 2
A. Pouring molten iron into a ladle, wherein the temperature of the molten iron is 1300 ℃, the slag quantity of the molten iron is 1cm, and the molten iron comprises the following components in percentage by mass: the content of C is 4.8%, the content of Mn is 0.4%, the content of S is 0.02%, the content of P is 0.12%, and the content of Si is 0.25%; removing pre-slag for 8min, inserting a stirring head into the molten iron below the liquid level by 1400mm, adding 6kg of desulfurizer into each ton of molten iron, stirring for 10min, lifting the stirring head to an upper limit after stopping stirring, and removing post-slag for 8min to obtain pretreated molten iron;
B. conveying the molten iron pretreated in the step A into a converter, adding scrap steel into the converter, and blowing to prepare molten steel, wherein the temperature of the molten steel is 1650 ℃; wherein the mass ratio of the scrap steel to the molten iron is 1: 4;
C. adding a carburant, lime, a deoxidizer, a pure calcium wire, titanium, boron and selenium into the molten steel in the step B in sequence, blowing argon, calming a steel ladle, and discharging slag to obtain refined molten steel;
D. c, injecting the refined molten steel obtained in the step C into a tundish, and flowing into a crystallizer through the tundish for continuous casting to obtain a continuous casting billet with the thickness of 200mm, wherein the temperature of the tundish is 1550 ℃, and the casting speed of the crystallizer is 1 m/min;
E. and D, heating the continuous casting slab in the step D by a heating furnace, wherein the soaking temperature is 1260 ℃, the total in-furnace time is 180min, roughly rolling the heated continuous casting slab to obtain an intermediate slab with the thickness of 35mm, finely rolling the intermediate slab by a 7-stand finishing mill group to obtain a steel plate, controlling the rolling speed at 2.5m/s, controlling the finishing temperature at 850 ℃, and finely rolling to obtain the steel plate with the thickness of 15 mm.
F. And E, carrying out laminar cooling on the steel plate obtained after the finish rolling in the step E, cooling to 600 ℃, and then coiling to obtain the titanium micro-alloy pipeline steel hot-rolled coil.
Example 3
A. Pouring molten iron into a ladle, wherein the temperature of the molten iron is 1280 ℃, the slag content of the molten iron is 2cm, and the molten iron comprises the following components in percentage by mass: the content of C is 4.2%, the content of Mn is 0.3%, the content of S is 0.028%, the content of P is 0.124%, and the content of Si is 0.51%; removing pre-slag for 5min, inserting a stirring head into the molten iron below the liquid level by 1200mm, adding 4.5kg of desulfurizer into each ton of molten iron, stirring for 8min, stopping stirring, lifting the stirring head to an upper limit, and removing post-slag for 6min to obtain pretreated molten iron;
B. b, conveying the molten iron pretreated in the step A into a converter, adding scrap steel into the converter, and blowing to prepare molten steel, wherein the temperature of the molten steel is 1660 ℃; wherein the mass ratio of the scrap steel to the molten iron is 1: 4;
C. adding a carburant, lime, a deoxidizer, a pure calcium wire, titanium, boron and selenium into the molten steel in the step B in sequence, blowing argon, calming a steel ladle, and discharging slag to obtain refined molten steel;
D. pouring the refined molten steel obtained in the step C into a tundish, and allowing the refined molten steel to flow into a crystallizer through the tundish for continuous casting to obtain a continuous casting billet of 200mm, wherein the temperature of the tundish is 1530 ℃, and the casting speed of the crystallizer is 1.2 m/min;
E. and D, heating the continuous casting slab in the step D by a heating furnace, wherein the soaking temperature is 1260 ℃, the total in-furnace time is 160min, roughly rolling the heated continuous casting slab to obtain an intermediate slab with the thickness of 35mm, finely rolling the intermediate slab by a 7-stand finishing mill group to obtain a steel plate, controlling the rolling speed at 2.6m/s, controlling the finish rolling temperature at 840 ℃, and finely rolling to obtain the steel plate with the thickness of 18 mm.
F. And E, carrying out laminar cooling on the steel plate obtained after the finish rolling in the step E, cooling to 600 ℃, and then coiling to obtain the titanium micro-alloy pipeline steel hot-rolled coil.
Example 4
A. Pouring molten iron into a ladle, wherein the temperature of the molten iron is 1300 ℃, the slag quantity of the molten iron is 1cm, and the molten iron comprises the following components in percentage by mass: the content of C is 4.8%, the content of Mn is 0.5%, the content of S is 0.03%, the content of P is 0.1%, and the content of Si is 0.5%; removing pre-slag for 6min, inserting a stirring head into the molten iron to be 1200mm below the liquid level, adding 4.5kg of desulfurizer into each ton of molten iron, stirring for 15min, stopping stirring, lifting the stirring head to an upper limit, and removing post-slag for 6min to obtain pretreated molten iron;
B. b, conveying the molten iron pretreated in the step A into a converter, adding scrap steel into the converter, and blowing to prepare molten steel, wherein the temperature of the molten steel is 1640 ℃; wherein the mass ratio of the scrap steel to the molten iron is 1: 4;
C. adding a carburant, lime, a deoxidizer, a pure calcium wire, titanium, boron and selenium into the molten steel in the step B in sequence, blowing argon, calming a steel ladle, and discharging slag to obtain refined molten steel;
D. c, injecting the refined molten steel obtained in the step C into a tundish, and flowing into a crystallizer through the tundish for continuous casting to obtain a continuous casting billet with the thickness of 200mm, wherein the temperature of the tundish is 1540 ℃, and the casting speed of the crystallizer is 1.4 m/min;
E. and D, heating the continuous casting slab in the step D by a heating furnace, wherein the soaking temperature is 1260 ℃, the total in-furnace time is 150min, roughly rolling the heated continuous casting slab to obtain an intermediate slab with the thickness of 35mm, finely rolling the intermediate slab by a 7-stand finishing mill group to obtain a steel plate, controlling the rolling speed at 2.7m/s, controlling the finish rolling temperature at 830 ℃, and finely rolling to obtain the steel plate with the thickness of 16 mm.
F. And E, carrying out laminar cooling on the steel plate obtained after the finish rolling in the step E, cooling to 590 ℃, and then coiling to obtain the titanium micro-alloy pipeline steel hot-rolled coil.
Example 5
A. Pouring molten iron into a ladle, wherein the temperature of the molten iron is 1280 ℃, the slag quantity of the molten iron is 1cm, and the molten iron comprises the following components in percentage by mass: the content of C is 4.1%, the content of Mn is 0.2%, the content of S is 0.03%, the content of P is 0.121%, and the content of Si is 0.32%; slagging off the pre-slag for 5min, inserting a stirring head into the molten iron below the liquid level by 1200mm, adding 8kg of desulfurizer into each ton of molten iron, stirring for 12min, lifting the stirring head to an upper limit after stopping stirring, and slagging off the pre-slag for 6min to obtain pretreated molten iron;
B. b, conveying the molten iron pretreated in the step A into a converter, adding scrap steel into the converter, and blowing to prepare molten steel, wherein the temperature of the molten steel is 1640 ℃; wherein the mass ratio of the scrap steel to the molten iron is 1: 4;
C. adding a carburant, lime, a deoxidizer, a pure calcium wire, titanium, boron and selenium into the molten steel in the step B in sequence, blowing argon, calming a steel ladle, and discharging slag to obtain refined molten steel;
D. pouring the refined molten steel obtained in the step C into a tundish, and flowing into a crystallizer through the tundish for continuous casting to obtain a continuous casting billet with the thickness of 200mm, wherein the temperature of the tundish is 1530 ℃, and the casting speed of the crystallizer is 1.5 m/min;
E. and D, heating the continuous casting slab in the step D by a heating furnace, wherein the soaking temperature is 1260 ℃, the total in-furnace time is 160min, roughly rolling the heated continuous casting slab to obtain an intermediate slab with the thickness of 35mm, finely rolling the intermediate slab by a 7-stand finishing mill group to obtain a steel plate, controlling the rolling speed at 2.9m/s, controlling the finishing temperature at 830 ℃, and finely rolling to obtain the steel plate with the thickness of 15 mm.
F. And E, performing laminar cooling on the steel plate obtained after the finish rolling in the step E, cooling to 610 ℃, and then coiling to obtain the titanium micro-alloy pipeline steel hot-rolled coil.
Comparative example 1
Compared with example 2, the difference is only that comparative example 1 adopts medium carbon ferromanganese and aluminum ingot to replace the deoxidizer in step C; the remaining steps were the same as in example 2.
Comparative example 2
Compared with example 2, the difference is only that comparative example 2 has no selenium added in step C, and the refined molten steel composition is shown in Table 2;
the remaining steps were the same as in example 2.
Comparative example 3
Compared with example 2, the only difference is that comparative example 3 has no boron added in step C, and the refined molten steel composition is shown in Table 2;
the remaining steps were the same as in example 2.
Comparative example 4
The only difference compared to example 2 is that comparative example 4 has no selenium and boron added in step C and the refined molten steel composition is shown in table 2;
the remaining steps were the same as in example 2.
Comparative example 5
Compared with the example 2, the difference is that the finishing temperature of the comparative example 5 is controlled to 780 ℃ in the step E, and the steel plate obtained after the finish rolling in the step F is cooled to 570 ℃ and then coiled;
the remaining steps were the same as in example 2.
Comparative example 6
Compared with example 2, the difference is that in comparative example 6, the finish rolling temperature is controlled at 880 ℃ in step E, and the steel plate obtained after finish rolling in step F is cooled to 650 ℃ and then coiled;
the remaining steps were the same as in example 2.
Table 1 composition mass% of deoxidizer%
TABLE 2 refined molten steel composition in percent by mass
Test experiments
1. Hardenability detection
The results of the Jominy test in GB/T225-.
2. Yield strength test
The yield strength test method of GB/T31922-.
3. Tensile strength testing
The tensile strength test is carried out by GB/T34219-2017, and the result is shown in Table 3.
4. Low temperature toughness test
The low-temperature Charpy impact test method of metal in GB 4159-1984 is adopted, the test temperature is-30 ℃, the low-temperature toughness is expressed by the impact energy, and the result is shown in Table 3.
5. Inclusion detection
The results of the tests carried out by the scanning electron microscope method in GB/T30834-2014 are shown in Table 3.
TABLE 3 mechanical Properties and inclusions of the titanium microalloy pipeline steel hot-rolled coil
As can be seen from Table 3, the titanium microalloy pipeline steel hot rolled coils prepared in the examples 1-5 have hardenability J46/49-10 or more, yield strength 506-528 MPa, tensile strength 603-630 MPa, impact power 216-222J at-30 ℃, B-type inclusions are not generated, D-type inclusions are controlled to be 0.5-1 level, and the problems of low hardenability, poor low-temperature toughness and high inclusion content of titanium microalloy pipeline steel in the prior art are solved.
Wherein the deoxidizer of examples 1 to 3 and 5 contains a compound corresponding to CaC2The condition of more than or equal to Ti and MgO is adopted, the yield strength of the prepared titanium micro-alloy pipeline steel hot-rolled coil is 523-528 MPa, the tensile strength is 630-637 MPa, D-type inclusions are controlled at 0.5 grade, and the CaC in the deoxidizer of the embodiment 42The titanium microalloy pipeline steel hot-rolled coil prepared in the example 4 has obviously reduced yield strength and tensile strength compared with the titanium microalloy pipeline steel hot-rolled coils prepared in the examples 1 to 3 and 5, the D-type inclusion is grade 1, and the deoxidizer meets the requirements of CaC2The condition of more than or equal to Ti and MgO improves the yield strength and the tensile strength of the titanium micro-alloy pipeline steel hot-rolled coil plate and reduces the content of D-type inclusions.
In the examples 1-5, the deoxidizer is adopted for LF refining, the yield strength of the prepared titanium microalloy pipeline steel hot-rolled coil is 506-528 MPa, the tensile strength is 603-630 MPa, the impact work is 216-222J at-30 ℃, B-type inclusions are not generated, and D-type inclusions are controlled to be 0.5-1 grade, while in the comparative example 1, medium-carbon ferromanganese and aluminum ingots are adopted for replacing the deoxidizer for LF refining, the yield strength, the tensile strength and the low-temperature toughness of the prepared titanium microalloy pipeline steel hot-rolled coil are all reduced, and the content of the B-type inclusions and the content of the D-type inclusions are increased.
Comparing examples 1-5 with comparative examples 2-4, wherein B, Se is not added in the LF refining process in the comparative example 4, the hardenability of the prepared titanium micro-alloy pipeline steel hot-rolled coil is J42/46-10, the yield strength is 486MPa, the tensile strength is 576MPa, Se is added in the LF refining process in the comparative example 3, and compared with the comparative example 4, the hardenability of the titanium micro-alloy pipeline steel hot-rolled coil prepared in the comparative example 3 is reduced; compared with the comparative example 4, the titanium microalloy pipeline steel hot-rolled coil prepared in the comparative example 2 has improved hardenability, the yield strength is improved by 16MPa, and the tensile strength is improved by 8 MPa; and B, Se is added in the embodiment 2, compared with the comparative example 4, the yield strength of the hot-rolled coil of the titanium microalloy pipeline steel prepared in the embodiment 2 is improved by 20-42 MPa, the tensile strength is improved by 27-61 MPa, and the hardenability is not reduced, so that the B, Se and other components in refined molten steel generate a mutual synergistic enhancement effect, and the yield strength and the tensile strength of the hot-rolled coil of the titanium microalloy pipeline steel are improved together.
In examples 1 to 5, the finish rolling temperature of the finish rolling was controlled to 820 to 850 ℃, the laminar cooling temperature was controlled to 590 to 620 ℃, the impact work of the produced titanium microalloy pipeline steel hot rolled plate at-30 ℃ was 216 to 222J, while the finish rolling temperature of the finish rolling in comparative example 5 was < 820 ℃, the laminar cooling temperature was < 590 ℃, the impact work of the produced titanium microalloy pipeline steel hot rolled plate at-30 ℃ was 196J, the finish rolling temperature of the finish rolling in comparative example 6 was > 820 ℃, the laminar cooling temperature was > 590 ℃, the impact work of the produced titanium microalloy pipeline steel hot rolled plate at-30 ℃ was 199J, and compared with examples 1 to 5, the low temperature toughness of the titanium microalloy pipeline steel hot rolled plates produced in comparative example 5 and comparative example 6 was significantly reduced, as a result, in the present invention, the finish rolling temperature was controlled to 820 to 850 ℃, the laminar cooling temperature was 590 to 620 ℃, the low-temperature toughness of the titanium micro-alloy pipeline steel hot-rolled coil is improved. The analysis reason is to ensure that the final rolling temperature is 820-850 ℃ to refine crystal grains, reduce the precipitation of larger TiN particles, control the laminar cooling temperature at 590-620 ℃ and ensure the precipitation strengthening of TiC and TiN, thereby improving the low-temperature toughness of the titanium microalloy pipeline steel hot-rolled coil. The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A rolling process for a hot-rolled coiled plate of titanium microalloy pipeline steel comprises the following steps: the method comprises the following steps of molten iron pretreatment, top-bottom combined blowing converter, LF refining, slab continuous casting, hot continuous rolling mill steel rolling, laminar cooling and coiling, and is characterized in that the LF refining process comprises the following steps: adding a carburant, lime, a deoxidizer, a pure calcium wire, titanium, boron and selenium into the molten steel in sequence, and then blowing argon, calming a steel ladle and discharging slag to obtain refined molten steel;
the deoxidizer comprises the following components in percentage by mass: 10 to 30 percent of Al and 5 to 20 percent of CaC21 to 5 percent of Ti, 0.1 to 2.0 percent of bentonite and 3.21 to 6.03 percent of SiO20.58 to 1.32 percent of FeO, 0.39 to 1.01 percent of MnO, 21.56 to 35.96 percent of CaO, 18.19 to 26.05 percent of Al2O33.47 to 6.32 percent of MgO;
the refined molten steel comprises the following components in percentage by mass: 0.060% -0.080% of C, 0.800% -0.950% of Mn, 0.120% -0.200% of Si, 0.025% -0.045% of Al, less than or equal to 0.010% of S, less than or equal to 0.015% of P, less than or equal to 0.008% of N, 0.055% -0.060% of Ti, 0.015% -0.020% of B, 0.050% -0.100% of Se, and the balance of Fe and impurities.
2. The rolling process of the titanium micro-alloy pipeline steel hot-rolled coil, according to claim 1, is characterized in that the mass percentages of the components of the deoxidizer are as follows: CaC2≥Ti+MgO。
3. The hot rolling and rolling process of the titanium microalloy pipeline steel as claimed in any one of claims 1 to 2, wherein the molten iron pretreatment is to pour molten iron into a ladle, slag before skimming is carried out for 5 to 8min, 4.5 to 8kg of desulfurizing agent is added into each ton of molten iron, stirring is carried out for 8 to 15min, and after stopping stirring, slag after skimming is carried out for 6 to 8min, so that pretreated molten iron is obtained.
4. The rolling process of the titanium microalloy pipeline steel hot-rolled coil, according to claim 3, characterized in that the molten iron comprises the following components in percentage by mass: c content is 4.2-5.1%, Mn content is 0.2-0.5%, S content is less than or equal to 0.03%, P content is less than or equal to 0.130%, and Si content is 0.25-0.55%; the temperature of the molten iron is equal to or more than 1280 ℃, and the slag carrying amount of the molten iron is equal to or less than 2 cm.
5. The rolling process of the titanium microalloy pipeline steel hot-rolled coil, according to claim 3, characterized in that the top furnace combined blowing converter is used for carrying the pretreated molten iron into the converter, then adding the waste steel into the converter for blowing to obtain molten steel, wherein the temperature of the molten steel is more than or equal to 1640 ℃.
6. The rolling process of the titanium microalloy pipeline steel hot-rolled coil, as recited in claim 5, wherein the argon blowing in the LF refining is performed by installing a gas supply element at the bottom of the steel ladle, and the argon is blown into the molten steel through a pipeline via the bottom gas supply element;
the ladle is calmed, namely the ladle is hung on a continuous casting ladle turret to wait for casting after argon blowing is finished, and the waiting time is less than or equal to 10 min;
and in the slag discharging step, after the steel ladle is killed, molten steel in the steel ladle flows into a tundish, and steel slag is discharged through a back slag discharging port at the back of the tundish.
7. The titanium microalloy pipeline steel hot-rolled coil rolling process as claimed in claim 6, wherein the slab continuous casting is to inject refined molten steel obtained after LF refining into a tundish, and flow the molten steel into a crystallizer through the tundish to carry out continuous casting to obtain a continuous casting billet;
the temperature of the tundish is 1530-1550 ℃, and the pulling speed of the crystallizer is 1-1.5 m/min.
8. The titanium microalloy pipeline steel hot-rolled coil rolling process as claimed in claim 7, wherein the hot continuous rolling mill is used for rolling steel, a continuous casting billet is heated at 1260 ℃, the heating time is not less than 150min, the heated continuous casting billet is subjected to rough rolling to obtain an intermediate plate blank, and the intermediate plate blank is subjected to finish rolling to obtain a 15-20 mm steel plate.
9. The rolling process of the titanium microalloy pipeline steel hot-rolled coil as claimed in claim 8, wherein the rolling speed of the finish rolling is 2.5-3.0 m/s, and the finishing temperature is controlled at 820-850 ℃.
10. The hot-rolled coil rolling process for the titanium microalloy pipeline steel as claimed in any one of claims 8 to 9, wherein the coiling is performed by coiling a finish-rolled steel plate which is cooled to 590 to 620 ℃ by laminar flow.
CN202010823610.7A 2020-08-17 2020-08-17 Smelting and rolling process for hot-rolled coil plate of titanium microalloy pipeline steel Pending CN111944952A (en)

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JPH04141519A (en) * 1990-10-02 1992-05-15 Nippon Steel Corp Production of structural steel plate excellent in toughness at low temperature and having high young's modulus
CN101613787A (en) * 2009-07-17 2009-12-30 凌幸福 Liquid steel high-efficiency composite refining agent
CN106319352A (en) * 2016-08-31 2017-01-11 安阳钢铁股份有限公司 Titanium microalloy strengthened pipeline steel hot-rolled coiled plate and production method thereof
CN106854737A (en) * 2016-12-15 2017-06-16 苏州赛斯德工程设备有限公司 A kind of outdoor cabinet anticorrosive steel
CN108754338A (en) * 2018-05-11 2018-11-06 敬业钢铁有限公司 A kind of production technology of high-magnetic induction, low-iron loss orientation silicon steel
CN110396637A (en) * 2019-08-30 2019-11-01 武安市裕华钢铁有限公司 The technique of low cost, short route, high efficiency production SPHC

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04141519A (en) * 1990-10-02 1992-05-15 Nippon Steel Corp Production of structural steel plate excellent in toughness at low temperature and having high young's modulus
CN101613787A (en) * 2009-07-17 2009-12-30 凌幸福 Liquid steel high-efficiency composite refining agent
CN106319352A (en) * 2016-08-31 2017-01-11 安阳钢铁股份有限公司 Titanium microalloy strengthened pipeline steel hot-rolled coiled plate and production method thereof
CN106854737A (en) * 2016-12-15 2017-06-16 苏州赛斯德工程设备有限公司 A kind of outdoor cabinet anticorrosive steel
CN108754338A (en) * 2018-05-11 2018-11-06 敬业钢铁有限公司 A kind of production technology of high-magnetic induction, low-iron loss orientation silicon steel
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