CN114150218A

CN114150218A - Q355NE hot-rolled round steel for high-speed rail bogie and production process

Info

Publication number: CN114150218A
Application number: CN202111391472.0A
Authority: CN
Inventors: 张群; 卢秉军; 阚开
Original assignee: Bengang Steel Plates Co Ltd
Current assignee: Bengang Steel Plates Co Ltd
Priority date: 2021-11-23
Filing date: 2021-11-23
Publication date: 2022-03-08

Abstract

The invention provides Q355NE hot-rolled round steel for a high-speed rail bogie and a production process thereof, wherein the steel comprises the following chemical components in percentage by weight: 0.14 to 0.18 percent of C, 0.17 to 0.40 percent of Si, 1.41 to 1.49 percent of Mn, 0.05 to 0.18 percent of Cr, 0.02 to 0.05 percent of V, less than or equal to 0.05 percent of Ni, less than or equal to 0.05 percent of Cu, less than or equal to 0.05 percent of Mo, 0.015 to 0.040 percent of Als, less than or equal to 0.012 percent of P, less than or equal to 0.010 percent of S, less than or equal to 15ppm of oxygen, and the balance of iron and inevitable impurities. In order to reduce the normalizing cost, the invention develops the technology that the alloy addition is used for replacing the normalizing treatment, and the added alloy elements are subjected to solid solution and precipitation in the hot working process, so that the final structure and performance of a steel product can be improved, the normalizing production procedures are reduced, and the production cost is also reduced.

Description

Q355NE hot-rolled round steel for high-speed rail bogie and production process

Technical Field

The invention relates to the technical field of ferrous metallurgy, in particular to Q355NE hot-rolled round steel for a high-speed rail bogie and a production process thereof.

Background

The high-speed rail bogie is a key component for ensuring the safe and stable operation of the train. With the continuous increase of train speed, the requirements on the performance of the bogie are higher and higher, and the steel Q355NE for the high-speed railway bogie is required to bear high-strength load and low-temperature impact load in a non-quenched and tempered state. The rolled steel Q355NE has the requirements of low-temperature impact property not lower than 34J at the temperature of minus 40 ℃, and has very high requirements on performance indexes such as yield strength, tensile strength and the like. Therefore, the requirements on steel component design, converter smelting, refining, continuous casting and the like are very strict in the production of the steel Q355NE for the high-speed rail bogie. If the quality of any link is not guaranteed, the strength and the impact performance of the steel can be seriously influenced to be unqualified.

Disclosure of Invention

The invention aims to provide Q355NE hot-rolled round steel for a high-speed rail bogie and a production process thereof, in order to reduce the normalizing cost, the invention develops the alloy addition to replace the normalizing treatment, and the added alloy elements are subjected to solid solution and precipitation in the hot working process, so that the final structure and performance of a steel product can be improved, the normalizing production procedures are reduced, and the production cost is reduced.

In order to achieve the purpose, the invention adopts the following technical scheme:

q355NE hot-rolled round steel for a high-speed rail bogie, which comprises the following chemical components in percentage by weight: 0.14 to 0.18 percent of C, 0.17 to 0.40 percent of Si, 1.41 to 1.49 percent of Mn, 0.05 to 0.18 percent of Cr, 0.02 to 0.05 percent of V, less than or equal to 0.05 percent of Ni, less than or equal to 0.05 percent of Cu, less than or equal to 0.05 percent of Mo, 0.015 to 0.040 percent of Als, less than or equal to 0.012 percent of P, less than or equal to 0.010 percent of S, less than or equal to 15ppm of oxygen content and the balance of iron and inevitable impurities in order to ensure the design of internal control components of the impact property of steel.

The carbon equivalent calculation formula is as follows: CEV (%) ═ C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15, CEV 0.40-0.45.

The invention has the following chemical components:

c, carbon C: the carbon content in the steel increases, the yield point and tensile strength increase, but the plasticity and impact properties decrease.

Silicon Si: can increase the strength, elasticity, heat resistance, acid resistance, resistivity and the like of the steel.

Manganese Mn: can improve the strength, hardness and wear resistance of the steel.

Chromium Cr: can increase the mechanical property and the wear resistance of the steel and can increase the quenching degree of the steel and the deformability of the quenched steel. Meanwhile, the hardness, elasticity, diamagnetic force and strength resistance of the steel can be increased, and the corrosion resistance, heat resistance and the like of the steel are increased.

Phosphorus P: the cold brittleness of the steel is generated, and the impact toughness of the steel is reduced; but the machinability of the steel can be improved.

S, sulfur: causing hot embrittlement of the steel, reducing the plasticity, impact toughness, fatigue strength, rust resistance, and the like of the steel. Meanwhile, the proper addition of the sulfur element can improve the finish of the processing surface of the steel; easy chip breaking during cutting and machining, small stress and energy consumption of the machining cutter and long service life of the cutter.

V, V: the structure crystal grains can be refined, and the strength and the toughness are improved. The carbide formed by vanadium and carbon can improve the hydrogen corrosion resistance under high temperature and high pressure.

A production process of Q355NE hot-rolled round steel for a high-speed rail bogie comprises the following steps:

1) smelting in a converter: 20-30 wt% of scrap steel and 70-80 wt% of molten iron; oxidizing oxygen, boiling violently, automatically flowing slag, and tapping at 1670-1680 ℃, wherein C is 0.12-0.13% and P is less than or equal to 0.010% during tapping, and slag making materials, pre-deoxidizers and ferroalloy are added during tapping 1/4-1/3; the adding amount of slag making materials and pre-deoxidizer per ton steel is as follows: 10-12 Kg/t magnesite, 20-22 Kg/t active lime, 12-15 Kg/t lime, 7-7.5 Kg/t iron-carbon balls and 100 Kg/furnace of rectangular blank heat-insulating agent.

2) And (4) LF furnace: the method comprises the steps of heating and slagging by adopting 20000-25000A high current, supplementing active lime when the slag surface fluctuates and molten steel and electric arcs are not exposed, adding 200-300 kg of active lime into each ton of steel, sampling for the first time after 5-8 min to analyze chemical components, supplementing alloy according to the target value of the chemical components, and recarburizing, wherein the alloy and carbon powder are added to argon gas flow to promote the rapid melting and homogenization of the alloy and the carbon powder. Adding 1-3 kg/t of diffusion deoxidizer when the temperature of molten steel reaches 1600-1610 ℃ for diffusion deoxidation, closing a furnace door for 10-12 min, sampling for the second time when the temperature of molten steel reaches 1630-1640 ℃ for analyzing chemical components to confirm deviation values of the content of each chemical element component from a target value, adding the diffusion deoxidizer to continuously adjust slag after taking away the secondary sample, and adding alloy: the addition amount of aluminum particles of the deoxidizer is 0.5-1 kg/t, the pH value of slag alkalinity is kept to be 2.5-3.5, the viscosity of the slag is 0.80-1.20 Pa.s, meanwhile, white slag smelting is kept for 20-30 min, when the temperature of molten steel reaches 1630-1640 ℃, final deoxidation is carried out, Al lines are fed for 0.5-1.0 kg/t, static argon blowing is started after the line feeding is finished, and the holding time is 10-20 min.

3) RH refining: controlling the argon pressure to be 0.1-0.3 MPa before starting a vacuum pump, slightly moving molten steel to be not exposed by a slag surface, timing when the vacuum degree reaches less than or equal to 100Pa, keeping for 10-15 min, supplementing aluminum particles and high manganese according to the components of the molten steel, simultaneously adjusting the argon pressure to be 0.3-0.5 MPa, and adding 200-220 kg of calcium silicate wire per furnace after the argon static blowing is finished;

4) continuous casting: continuous casting 1545-1555 ℃, the temperature of the tundish 1530-1536 ℃, the pulling speed 0.5-0.6 m/min, the control of the tundish H is less than or equal to 3ppm, the electromagnetic stirring current of the crystallizer is 400A +/-10A, the electromagnetic stirring current of the tail end is 330A +/-10A, and the whole process frequency is 8Hz +/-1 Hz; the whole process is casting-protected, and the crystallizer casting powder is medium-carbon steel casting powder; the casting blank cutting adopts the mode of automatically adding manual work and combining, the red steel of continuous casting blank fills up the bottom, and two stove casting blanks of top pressure guarantee the straightness, and the heat preservation time is 30 ~ 40 h.

5) Rolling: cogging by adopting a 1150mm BD blooming mill, rolling for 7 times, and rolling reduction: 60 +/-1 mm of the 1 st pass, 70 +/-1 mm of the 2 nd pass, 66 +/-1 mm of the 3 rd pass, 57 +/-1 mm of the 4 th pass, 66 +/-1 mm of the 5 th pass, 72 +/-1 mm of the 6 th pass and 72 +/-1 mm of the 7 th pass, pass through 3 frames of 850mm rolling mills and 1 frame of 735mm rolling mills, and then enter 8 frames of continuous rolling units for rolling.

The mechanical properties and the low-temperature impact property at minus 40 ℃ of the invention are shown in Table 1;

TABLE 1 mechanical properties and-40 ℃ Low temperature impact Properties of the inventive products

Compared with the prior art, the invention has the beneficial effects that:

1) the invention adopts the 180t converter + LF + RH + rectangular billet (350mm multiplied by 470mm) process to produce the steel Q355NE for the high-speed rail bogie, thereby ensuring the purity of the steel and the continuous casting property.

2) The reasonable component design of the invention ensures the internal structure, mechanical property and impact property of the steel.

3) The macrostructure, non-metallic inclusions, mechanical property and low-temperature impact property of the finished steel product meet the quality requirement of high-end products.

Drawings

FIG. 1 is a flow chart of the converter production process of the present invention.

In the figure: 1-molten iron desulphurization process, 2-converter process, 3-LF furnace process, 4-RH furnace process, 5-continuous casting process and 6-rectangular casting blank.

Detailed Description

The following examples further illustrate embodiments of the present invention.

The invention adopts the 180t converter + LF + RH + rectangular billet (350mm multiplied by 470mm) process to produce the steel Q355NE for the high-speed rail bogie, thereby ensuring the purity of the steel and the continuous casting property.

Example (b):

the chemical compositions of examples 1-5 are shown in Table 2; the macrostructures of the products of examples 1 to 5 are shown in Table 3; non-metallic inclusions of the products of examples 1-5 are shown in Table 4; the mechanical properties of the products of examples 1 to 5 are shown in Table 5; the impact properties of the products of examples 1 to 5 are shown in Table 6.

TABLE 2 chemical composition (wt%) of steel of each example

Element(s)	C	Si	Mn	Cr	P	S	Ni	V	Mo	Alt	Cu	CEV
													Example 1	0.16	0.27	1.45	0.14	0.009	0.005	0.02	0.03	0.02	0.025	0.02	0.43
Example 2	0.15	0.23	1.42	0.12	0.010	0.002	0.01	0.02	0.01	0.020	0.01	0.41
													Example 3	0.17	0.35	1.43	0.10	0.008	0.005	0.02	0.04	0.01	0.030	0.01	0.42
Example 4	0.14	0.30	1.48	0.06	0.005	0.003	0.01	0.05	0.02	0.035	0.02	0.44
													Example 5	0.18	0.20	1.46	0.16	0.004	0.002	0.02	0.03	0.01	0.038	0.01	0.40

The invention relates to a production process of Q355NE hot-rolled round steel for a high-speed rail bogie, which comprises the following steps: molten iron in a blast furnace → molten iron pretreatment → 180t converter smelting → a refining furnace LF → vacuum degassing RH → continuous casting of a rectangular billet with the thickness of 350mm and 470mm → heating of a walking beam furnace → high-pressure water descaling → rolling of a blooming mill → a tandem mill group → slow cooling → finishing → flaw detection → inspection → warehousing, which specifically comprises the following steps:

1) smelting in a converter: 20-30 wt% of scrap steel and 70-80 wt% of molten iron; oxidizing oxygen, boiling violently, automatically flowing slag, and tapping at 1670-1680 ℃, wherein C is 0.12-0.13% and P is less than or equal to 0.010% during tapping, and slag charge, pre-deoxidizer and ferroalloy are added during tapping 1/4-1/3; adding auxiliary materials (slag charge and pre-deoxidizer) per ton of steel: 10-12 Kg/t magnesite, 20-22 Kg/t active lime, 12-15 Kg/t lime, 7-7.5 Kg/t iron-carbon balls and 100 Kg/furnace of rectangular blank heat-insulating agent.

2) And (4) LF furnace: the method comprises the steps of heating and slagging by adopting 20000-25000A high current, supplementing active lime when the slag surface fluctuates and molten steel and electric arcs are not exposed, adding 200-300 kg of active lime into each ton of steel, sampling for the first time after 5min to analyze chemical components, supplementing alloy according to target values of the chemical components, and recarburizing, wherein the alloy and carbon powder are added to argon gas flow so as to promote quick melting and homogenization of the alloy and the carbon powder. Adding a diffusion deoxidizer for diffusion deoxidation when the temperature of the molten steel reaches 1600-1610 ℃, closing the furnace door for 10min, sampling for the second time when the temperature of the molten steel reaches 1630-1640 ℃, analyzing chemical components to confirm deviation values of the content of each chemical element component from target values, supplementing the diffusion deoxidizer for continuously regulating slag after the secondary samples are taken away, and supplementing alloy; 0.5-1 kg/t of deoxidizer aluminum particles, keeping the pH value of slag at 2.5-3.5, keeping the viscosity of slag at 0.80-1.20 Pa.s, continuously keeping white slag smelting for 20-30 min, performing final deoxidation when the temperature of molten steel reaches 1630-1640 ℃, feeding 0.5-1.0 kg/t of Al wires, starting static argon blowing after wire feeding, and keeping for 10-20 min.

3) RH refining: controlling the argon pressure to be 0.1-0.3 MPa before starting a vacuum pump, slightly moving molten steel to be not exposed by a slag surface, timing when the vacuum degree reaches 100Pa, keeping for 10-15 min, supplementing aluminum particles and high manganese according to the components of the molten steel, simultaneously adjusting the argon pressure to be 0.3-0.5 MPa, and adding a calcium silicate wire to 200 kg/furnace after the argon static blowing is finished;

4) continuous casting: continuous casting 1545-1555 ℃, the temperature of the tundish 1530-1536 ℃, the pulling speed 0.5m/min, the control of the tundish H is less than or equal to 3ppm, the electromagnetic stirring current of the crystallizer is 400A, the electromagnetic stirring current of the tail end is 330A, and the frequency is 8 Hz; the whole process is casting-protected, and the crystallizer casting powder is medium-carbon steel casting powder; the casting blank cutting adopts the mode of automatically adding manual work and combining, the red steel of continuous casting blank fills up the bottom, and two stove casting blanks of top pressure guarantee the straightness, and the heat preservation time is 30 ~ 40 h.

5) Rolling: cogging by adopting a 1150mm BD blooming mill, rolling for 7 times, and rolling reduction: 60mm for the 1 st pass, 70mm for the 2 nd pass, 66mm for the 3 rd pass, 57mm for the 4 th pass, 66mm for the 5 th pass, 72mm for the 6 th pass and 72 for the 7 th pass, passing through 3 stands of 850mm rolling mills and 1 stand of 735mm rolling mills, and then entering into 8 stands of continuous rolling mills for rolling.

TABLE 3 macrostructures of the products of the examples

Examples	Center porosity	Generally loose	Ingot type segregation
				1	0.5	1.0	1.0
2	0.5	1.0	1.0
				3	0.5	1.0	1.0
4	0.5	1.0	0.5
				5	0.5	1.0	0.5

TABLE 4 non-metallic inclusions in the products of the examples

TABLE 5 mechanical Properties of the products of the examples

Examples	Specification of	R_eH/MPa	R_M/MPa	A/％	Yield ratio
						1	Φ180	360	550	30.5	0.65
2	Φ150	355	545	32.0	0.65
						3	Φ110	361	559	32.0	0.65
4	Φ100	335	543	31.0	0.62
						5	Φ150	340	528	33.5	0.64

TABLE 6 impact properties of the products of the examples

Examples	Specification of	Temperature of	Impact single value A	Impact single value B	Impact single value C	Mean value of impact
							1	Φ180	-40℃	58	70	70	66
2	Φ150	-40℃	50	48	48	49
							3	Φ110	-40℃	50	60	44	51
4	Φ100	-40℃	92	100	152	115
							5	Φ150	-40℃	152	96	50	99

This patent application compares with prior art: 1) other methods have poor quality stability, and the macrostructure, nonmetallic inclusion, mechanical property and low-temperature impact property of the invention are not stable. 2) The smelting cost, the rolling cost and other process costs of other methods are higher than the production process cost of the invention.

Claims

1. The Q355NE hot-rolled round steel for the high-speed rail bogie is characterized in that the steel comprises the following chemical components in percentage by weight: 0.14 to 0.18 percent of C, 0.17 to 0.40 percent of Si, 1.41 to 1.49 percent of Mn, 0.05 to 0.18 percent of Cr, 0.02 to 0.05 percent of V, less than or equal to 0.05 percent of Ni, less than or equal to 0.05 percent of Cu, less than or equal to 0.05 percent of Mo, 0.015 to 0.040 percent of Als, less than or equal to 0.012 percent of P, less than or equal to 0.010 percent of S, less than or equal to 15ppm of oxygen, and the balance of iron and inevitable impurities.

2. The Q355NE hot-rolled round steel for high-speed rail bogies according to claim 1, wherein the carbon equivalent calculation formula is as follows: CEV (%) ═ C + Mn/6+ (Cr + Mo + V)/5+ (Ni + Cu)/15, CEV 0.40-0.45.

3. A process for producing Q355NE hot-rolled round steel for a high-speed railway bogie as claimed in claim 1 or 2, which comprises the steps of:

1) smelting in a converter: the tapping temperature is 1670-1680 ℃, the C is 0.12-0.13% and the P is less than or equal to 0.010% during tapping, and slag charge, pre-deoxidizer and ferroalloy are added during tapping;

2) and (4) LF furnace: heating up by adopting 20000-25000A heavy current to melt slag, supplementing active lime, supplementing alloy after 5-8 min, adding carbon, adding a diffusion deoxidizer to perform diffusion deoxidation when the temperature of molten steel reaches 1600-1610 ℃, supplementing the diffusion deoxidizer to continue slag adjustment when the temperature of molten steel reaches 1630-1640 ℃, supplementing alloy, keeping the pH value of molten slag at 2.5-3.5 and the viscosity of molten slag at 0.80-1.20 Pa.s, continuing to keep white slag smelting for 20-30 min, feeding Al line at 0.5-1.0 kg/t by performing final deoxidation when the temperature of molten steel reaches 1630-1640 ℃, starting static argon blowing after the line feeding is finished, and keeping for 10-20 min.

3) RH refining: controlling the argon pressure to be 0.1-0.3 MPa before starting the vacuum pump, starting timing when the vacuum degree reaches less than or equal to 100Pa, keeping for 10-15 min, supplementing aluminum particles and high manganese according to the components of molten steel, adjusting the argon pressure to be 0.3-0.5 MPa, and adding a calcium silicate wire after the argon static blowing is finished;

4) continuous casting: and (3) carrying out continuous casting 1545-1555 ℃, the temperature of the tundish 1530-1536 ℃, the pulling speed is 0.5-0.6 m/min, the control of the tundish H is less than or equal to 3ppm, and the heat preservation time of the continuous casting billet is 30-40H.

4. The process for producing the Q355NE hot-rolled round steel for the high-speed railway bogie according to claim 3, wherein the steel scrap is 20-30 wt% and the molten iron is 70-80 wt% in the converter smelting in the step 1).

5. The process for producing Q355NE hot-rolled round steel for high-speed rail bogie according to claim 3, wherein slag forming material, pre-deoxidizer and ferroalloy are added during the step 1) tapping of 1/4-1/3; adding slag making materials and pre-deoxidizer into per ton of steel: 10-12 Kg/t magnesite, 20-22 Kg/t active lime, 12-15 Kg/t lime, 7-7.5 Kg/t iron-carbon balls and 100 Kg/furnace of rectangular blank heat-insulating agent.

6. The production process of Q355NE hot-rolled round steel for high-speed rail bogie according to claim 3, wherein the amount of supplementary active lime added in step 2) is 200-300 kg per ton of steel.

7. The process for producing the Q355NE hot-rolled round steel for the high-speed railway bogie according to claim 3, wherein in the step 4), the electromagnetic stirring current of the crystallizer is 400A +/-10A, the electromagnetic stirring current of the tail end is 330A +/-10A, and the whole process frequency is 8Hz +/-1 Hz; the whole process is casting-protected, and the crystallizer casting powder is medium-carbon steel casting powder.