阅读说明：本技术 一种高纯净度珠光体钢的冶炼方法 (Smelting method of high-purity pearlite steel ) 是由 杨海西 韩报明 胡建利 樊利智 蔡晓云 于 2021-07-24 设计创作，主要内容包括：通过对成分的改进、对冶炼工艺、精炼工艺、成分的控制,提供一种高纯净度珠光体钢的冶炼方法,其包括KR法铁水预处理,顶底复吹转炉冶炼,LF炉精炼和VD处理,可以得到具有更好的硬度和更优良的耐磨性能、耐腐蚀性能的珠光体钢。(The method for smelting the high-purity pearlite steel comprises the steps of KR method molten iron pretreatment, top-bottom combined blown converter smelting, LF furnace refining and VD treatment, and the pearlite steel with better hardness and better wear resistance and corrosion resistance can be obtained.)

1. A smelting method of high-purity pearlite steel is characterized by comprising the following steps:

(1) the sulfur content of the molten iron after the molten iron pretreatment is less than or equal to 0.01 percent;

(2) smelting in a top-bottom combined blown converter;

(3) refining in an LF furnace, wherein the refining slag adopted in the LF furnace contains 48-50% of CaO and 225-28% of SiO in percentage by mass;

(4) and VD treatment, wherein the deep vacuum degassing time is more than or equal to 15min, the vacuum degree is not more than 0.08KPa, the argon blowing flow is 250-280 NL/min, and the soft blowing time after vacuum degassing is more than or equal to 18 min.

2. A smelting method of high-purity pearlite steel is characterized by comprising the following steps:

(1) the sulfur content of the molten iron after the molten iron pretreatment is less than or equal to 0.01 percent;

(2) smelting in a top-bottom combined blown converter, adopting a 120t converter, drawing carbon and tapping to ensure that phosphorus in steel is less than 0.01 percent; controlling the end point carbon of the converter to be 0.15-0.40% and controlling the temperature to be 1590-1620 ℃; slag stopping and tapping, wherein the thickness of a slag layer is 0-30 mm; adding a deoxidizer in the process of smelting molten steel and tapping in a converter, wherein the deoxidizer contains 72-73% of Si, 11-12% of Ca, 11-12% of Ba, 1-2% of SiC and the balance of Fe + Al + impurity elements in percentage by mass, and the adding amount of the deoxidizer is 1.5-2.2 kg/t of molten steel;

(3) refining in an LF furnace, controlling the flow of bottom blown argon at 150-180 NL/min after the bottom blown argon is blown for 4-5 min, deoxidizing and refining by using calcium carbide for 5-10min, then adding ferrovanadium and ferrochrome for alloying for 3-5min, adjusting the flow of argon at 180-200 NL/min to promote the dissolution and absorption of alloy elements, and then adding ferronickel and ferrocopper for alloying for 3-5 min; then feeding 2m of calcium-silicon wire per ton of steel and rare earth, adjusting the flow of argon to be 50-120 NL/min, and blowing argon for 10-15 min to promote large-particle impurities to fully float upwards and then discharging the molten steel; the LF furnace adopts specific refining slag which consists of 48-50% of CaO, 225-28% of SiO, 8-15% of MgO, 78-10% of Al2O 35, 25-10% of CaF and less than or equal to 1.5% of FeO in percentage by mass;

(4) VD treatment, wherein the deep vacuum degassing time is more than or equal to 15min, the vacuum degree is not more than 0.08KPa, the argon blowing flow is 250-280 NL/min, and the soft blowing time after vacuum degassing is more than or equal to 18 min;

the pearlite steel comprises the following components in percentage by weight: 0.83-0.88% of C; 0.7-0.8% of Si; 0.9-1.0% of Mn; 0.70-0.75% of Cr; v0.02-0.04%, Cu 0.02-0.04%, Ni 0.02-0.04%, P less than or equal to 0.008%; s is less than or equal to 0.005 percent; al is less than or equal to 0.004%, Ce: 0.001-0.005%, La 0.001-0.005%, H less than or equal to 0.00015%, N less than or equal to 0.006%, O less than or equal to 0.002%, and the balance Fe and inevitable impurities.

3. The method of claim 2, wherein: the deoxidizer contains, by mass, 72% of Si, 11% of Ca, 11% of Ba, 1% of SiC, and the balance of Fe + Al + impurity elements.

4. The method of claim 2, wherein: the deoxidizer contains 73 mass percent of Si, 12 mass percent of Ca, 12 mass percent of Ba, 2 mass percent of SiC and the balance of Fe + Al + impurity elements.

5. The method of claim 2, wherein: the refining slag comprises 48% of CaO, 225% of SiO, 10% of MgO, 38% of Al2O, 28% of CaF and less than or equal to 1.5% of FeO by mass percentage.

6. The method of claim 2, wherein: the refining slag comprises, by mass, 50% of CaO, 228% of SiO, 8% of MgO, 8% of Al2O 36%, 27% of CaF and less than or equal to 1.5% of FeO.

Technical Field

The invention relates to the field of steel, in particular to a method for smelting a high-purity pearlitic steel rail.

Background

The railway transportation has the characteristics of high speed, safety and high cost performance, the wire net is more and more tense along with the continuous improvement of the running speed, and the steel rail can be corroded in part of areas due to the influence of the climate environment, so that the abrasion of the steel rail can be accelerated and fatigue cracks can be generated obviously. If the crack expands a little bit and finally leads to rail breakage, the largest safety accident can be caused. Therefore, the requirements on the crack resistance, the wear resistance and the corrosion resistance of the steel rail are higher and higher.

Pearlite is a typical type of rail grade, and pearlite steel has a wide range of applications, and comprises lamellar cementite phases and ferrite phases alternately arranged. There are many factors that affect the mechanical properties of pearlitic steel, one of the important factors is the pearlite plate spacing. The strength of the pearlite steel can be improved and the hardness can be improved by thinning the pearlite inter-sheet distance. The pearlite inter-lamellar spacing also affects the plasticity of pearlite steel, and when the pearlite inter-lamellar spacing becomes smaller, the number of lamellae participating in deformation is larger, the deformation is more uniform, so that the plasticity of the steel is improved.

The purity and stability of the rail are important factors affecting quality and performance. In the smelting and rolling process, non-metallic inclusions and some harmful elements are inevitably present in the steel material along with the change of temperature. The key of the purity control is the control of hydrogen, total oxygen, aluminum, non-metallic inclusions and the like in steel, aluminum deoxidation is frequently used in the smelting process of conventional steel, but aluminum can form alumina inclusions to cause the cracks of steel rails. In addition, the refining process has great influence on P, S, O and inclusion control, if the continuous casting process is not controlled properly, gas enters molten steel, and a large amount of inclusions are formed, so that good deoxidation technology and deoxidation product removal are always desired in the smelting process, the refining process and the continuous casting process.

Disclosure of Invention

The invention aims to provide a method for smelting pearlitic steel with high purity, better hardness, and better wear resistance and corrosion resistance by improving components and controlling a smelting process and a refining process.

The invention provides a method for smelting a high-purity pearlite steel rail, which is characterized by comprising the following steps of:

(1) the sulfur content of the molten iron after the molten iron pretreatment is less than or equal to 0.01 percent;

(2) smelting in a top-bottom combined blown converter;

(3) refining in an LF furnace, wherein the refining slag adopted in the LF furnace contains 48-50% of CaO and 225-28% of SiO in percentage by mass;

(4) and VD treatment, wherein the deep vacuum degassing time is more than or equal to 15min, the vacuum degree is not more than 0.08KPa, the argon blowing flow is 250-280 NL/min, and the soft blowing time after vacuum degassing is more than or equal to 18 min.

Further, the invention provides a method for smelting high-purity pearlite steel, which is characterized by comprising the following steps:

(1) the sulfur content of the molten iron after the molten iron pretreatment is less than or equal to 0.01 percent;

(2) smelting in a top-bottom combined blown converter, adopting a 120t converter, drawing carbon and tapping to ensure that phosphorus in steel is less than 0.01 percent; controlling the end point carbon of the converter to be 0.15-0.40% and controlling the temperature to be 1590-1620 ℃; slag stopping and tapping, wherein the thickness of a slag layer is 0-30 mm; adding a deoxidizer in the process of smelting molten steel and tapping in a converter, wherein the deoxidizer contains 72-73% of Si, 11-12% of Ca, 11-12% of Ba, 1-2% of SiC and the balance of Fe + Al + impurity elements in percentage by mass, and the adding amount of the deoxidizer is 1.5-2.2 kg/t of molten steel;

(3) refining in an LF furnace, controlling the flow of bottom blown argon at 150-180 NL/min after the bottom blown argon is blown for 4-5 min, deoxidizing and refining by using calcium carbide for 5-10min, then adding ferrovanadium and ferrochrome for alloying for 3-5min, adjusting the flow of argon at 180-200 NL/min to promote the dissolution and absorption of alloy elements, and then adding ferronickel and ferrocopper for alloying for 3-5 min; then feeding 2m of calcium-silicon wire per ton of steel and rare earth, adjusting the flow of argon to be 50-120 NL/min, and blowing argon for 10-15 min to promote large-particle impurities to fully float upwards and then discharging the molten steel; the LF furnace adopts specific refining slag which consists of 48-50% of CaO, 225-28% of SiO, 8-15% of MgO, 78-10% of Al2O 35, 25-10% of CaF and less than or equal to 1.5% of FeO in percentage by mass;

(4) VD treatment, wherein the deep vacuum degassing time is more than or equal to 15min, the vacuum degree is not more than 0.08KPa, the argon blowing flow is 250-280 NL/min, and the soft blowing time after vacuum degassing is more than or equal to 18 min;

the pearlite steel comprises the following components in percentage by weight: 0.83-0.88% of C; 0.7-0.8% of Si; 0.9-1.0% of Mn; 0.70-0.75% of Cr; v0.02-0.04%, Cu 0.02-0.04%, Ni 0.02-0.04%, P less than or equal to 0.008%; s is less than or equal to 0.005 percent; al is less than or equal to 0.004%, Ce: 0.001-0.005%, La 0.001-0.005%, H less than or equal to 0.00015%, N less than or equal to 0.006%, O less than or equal to 0.002%, and the balance Fe and inevitable impurities.

The tensile strength of the steel manufactured by the conventional rolling method in the field is more than or equal to 1180MPa, the elongation A after fracture is more than or equal to 12 percent, the pearlite inter-lamellar spacing is less than or equal to 0.17 micrometer, and the hardness is 400-430 HB.

Further, the deoxidizer contains, by mass%, 72% of Si, 11% of Ca, 11% of Ba, 1% of SiC, and the balance of Fe + Al + impurity elements.

Further, the deoxidizer contains 73% by mass of Si, 12% by mass of Ca, 12% by mass of Ba, 2% by mass of SiC, and the balance of Fe + Al + impurity elements.

Further, the refining slag comprises 48% of CaO, 225% of SiO, 10% of MgO, 38% of Al2O, 28% of CaF and less than or equal to 1.5% of FeO by mass percentage.

Further, the refining slag comprises, by mass, 50% of CaO, 228% of SiO, 8% of MgO, 36% of Al2O, 27% of CaF and less than or equal to 1.5% of FeO.

The invention has the beneficial effects that:

most of the deoxidizers in the prior steel smelting technology are aluminum deoxidization and silicon deoxidization, and a small part of deoxidizers adopt composite alloying deoxidization. However, as the prices of deoxidizing agents of Si, Ca and Ba are higher, in order to reduce production cost, a small amount of SiC is gradually considered to be used for assisting deoxidation, but the SiC content cannot be added too much, because the addition of SiC causes carburetion of molten steel, and is not favorable for accurate control of the C content.

The use of refining slag is common in the field, and the general components are CaO + SiO2+ MgO + Al2O3, but not all the refining slag have universality and have certain degree of matching with the process and the components, so the control of the content of the refining slag should be matched with the actual application scene. In addition, a small amount of CaF2 was also used in consideration of the viscosity, fluidity, desulfurization ability, and oxygen potential of the refining slag.

The content of O, N, H element is obviously reduced through the specific design of deoxidizer and refining slag, the specific improvement of refining process and the component of pearlite steel, the improvement of strength, hardness, wear resistance and crack resistance is obviously improved, and the method has obvious popularization significance. Class A inclusions are not more than 0.5 grade, class B, C inclusions are 0 grade, and class D inclusions are not more than 0.5 grade;

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

Examples 1 to 4

A smelting method of a high-purity pearlite steel rail is characterized by comprising the following steps:

(1) the sulfur content of the molten iron after the molten iron pretreatment is less than or equal to 0.01 percent;

(2) smelting in a top-bottom combined blown converter, adopting a 120t converter, drawing carbon and tapping to ensure that phosphorus in steel is less than 0.01 percent; controlling the end point carbon of the converter to be 0.15-0.40% and controlling the temperature to be 1590-1620 ℃; slag stopping and tapping, wherein the thickness of a slag layer is 0-30 mm; adding a deoxidizer in the process of smelting molten steel and tapping in a converter, wherein the adding amount of the deoxidizer is 1.5-2.2 kg/t molten steel;

(3) refining in an LF furnace, controlling the flow of bottom blown argon at 150-180 NL/min after the bottom blown argon is blown for 4-5 min, deoxidizing and refining by using calcium carbide for 5-10min, then adding ferrovanadium and ferrochrome for alloying for 3-5min, adjusting the flow of argon at 180-200 NL/min to promote the dissolution and absorption of alloy elements, and then adding ferronickel and ferrocopper for alloying for 3-5 min; then feeding 2m of calcium-silicon wire per ton of steel and rare earth, adjusting the flow of argon to be 50-120 NL/min, and blowing argon for 10-15 min to promote large-particle impurities to fully float upwards and then discharging the molten steel; the LF furnace adopts specific refining slag which consists of 48-50% of CaO, 225-28% of SiO, 8-15% of MgO, 78-10% of Al2O 35, 25-10% of CaF and less than or equal to 1.5% of FeO in percentage by mass;

(4) VD treatment, wherein the deep vacuum degassing time is more than or equal to 15min, the vacuum degree is not more than 0.08KPa, the argon blowing flow is 250-280 NL/min, and the soft blowing time after vacuum degassing is more than or equal to 18 min;

the pearlite steel comprises the following components in percentage by weight: 0.83-0.88% of C; 0.7-0.8% of Si; 0.9-1.0% of Mn; 0.70-0.75% of Cr; v0.02-0.04%, Cu 0.02-0.04%, Ni 0.02-0.04%, P less than or equal to 0.008%; s is less than or equal to 0.005 percent; al is less than or equal to 0.004%, Ce: 0.001-0.005%, La 0.001-0.005%, H less than or equal to 0.00015%, N less than or equal to 0.006%, O less than or equal to 0.002%, and the balance Fe and inevitable impurities.

Comparative examples 1 to 3

Comparative examples 1 to 3 are different from examples 1 to 4 in the oxygen scavenger.

The oxygen scavengers used in examples 1 to 4 and comparative examples 1 to 3 have the following effects as shown in Table 1 below:

	Si	Ca	Ba	SiC	balance of	[H][N][O]
							Example 1	72	11	11	1	Fe + Al + impurity elements	[H]≤0.00015、[N]≤0.006、[O]≤0.002
Example 2	72.3	11.4	11.4	1.2	Fe + Al + impurity elements	[H]≤0.00015、[N]≤0.006、[O]≤0.002
							Example 3	72.7	11.8	11.8	1.6	Fe + Al + impurity elements	[H]≤0.00015、[N]≤0.006、[O]≤0.002
Example 4	73	12	12	2	Fe + Al + impurity elements	[H]≤0.00015、[N]≤0.006、[O]≤0.002
							Comparative example 1	50	15	15	0	Fe + Al + impurity elements	[H]≤0.0005、[N]≤0.015、[O]≤0.009
Comparative example 2	60	18	18	0	Fe + Al + impurity elements	[H]≤0.0005、[N]≤0.015、[O]≤0.007
							Comparative example 3	60	18	18	4	Fe + Al + impurity elements	[H]≤0.0004、[N]≤0.012、[O]≤0.007

Examples 5 to 6

A smelting method of a high-purity pearlite steel rail is characterized by comprising the following steps:

(1) the sulfur content of the molten iron after the molten iron pretreatment is less than or equal to 0.01 percent;

(2) smelting in a top-bottom combined blown converter, adopting a 120t converter, drawing carbon and tapping to ensure that phosphorus in steel is less than 0.01 percent; controlling the end point carbon of the converter to be 0.15-0.40% and controlling the temperature to be 1590-1620 ℃; slag stopping and tapping, wherein the thickness of a slag layer is 0-30 mm; adding a deoxidizer in the process of smelting molten steel and tapping in a converter, wherein the deoxidizer contains 72-73% of Si, 11-12% of Ca, 11-12% of Ba, 1-2% of SiC and the balance of Fe + Al + impurity elements in percentage by mass, and the adding amount of the deoxidizer is 1.5-2.2 kg/t of molten steel;

(3) refining in an LF furnace, controlling the flow of bottom blown argon at 150-180 NL/min after the bottom blown argon is blown for 4-5 min, deoxidizing and refining by using calcium carbide for 5-10min, then adding ferrovanadium and ferrochrome for alloying for 3-5min, adjusting the flow of argon at 180-200 NL/min to promote the dissolution and absorption of alloy elements, and then adding ferronickel and ferrocopper for alloying for 3-5 min; then feeding 2m of calcium-silicon wire per ton of steel and rare earth, adjusting the flow of argon to be 50-120 NL/min, and blowing argon for 10-15 min to promote large-particle impurities to fully float upwards and then discharging the molten steel; the LF furnace adopts specific refining slag;

(4) VD treatment, wherein the deep vacuum degassing time is more than or equal to 15min, the vacuum degree is not more than 0.08KPa, the argon blowing flow is 250-280 NL/min, and the soft blowing time after vacuum degassing is more than or equal to 18 min;

the pearlite steel comprises the following components in percentage by weight: 0.83-0.88% of C; 0.7-0.8% of Si; 0.9-1.0% of Mn; 0.70-0.75% of Cr; v0.02-0.04%, Cu 0.02-0.04%, Ni 0.02-0.04%, P less than or equal to 0.008%; s is less than or equal to 0.005 percent; al is less than or equal to 0.004%, Ce: 0.001-0.005%, La 0.001-0.005%, H less than or equal to 0.00015%, N less than or equal to 0.006%, O less than or equal to 0.002%, and the balance Fe and inevitable impurities.

Comparative examples 4 to 7

Comparative examples 4 to 7 are different from examples 5 to 6 in the refining slag. The parameters and effects are shown in the following table 2:

	CaO	SiO2	MgO	Al2O3	CaF2	[H][N][O]
							example 5	48	25	10	8	8	[H]≤0.00015、[N]≤0.006、[O]≤0.002
Example 6	50	28	8	6	7	[H]≤0.00015、[N]≤0.006、[O]≤0.002
							Comparative example 4	48	26	18	8	0	[H]≤0.0008、[N]≤0.020、[O]≤0.006
Comparative example 5	50	26	17	7	0	[H]≤0.0008、[N]≤0.015、[O]≤0.006
							Comparative example 6	48	26	20	5	1	[H]≤0.0007、[N]≤0.017、[O]≤0.006
Comparative example 7	50	27	16	4	3	[H]≤0.0007、[N]≤0.010、[O]≤0.006

Example 7

A smelting method of a high-purity pearlite steel rail is characterized by comprising the following steps:

(1) the sulfur content of the molten iron after the molten iron pretreatment is less than or equal to 0.01 percent;

(2) smelting in a top-bottom combined blown converter, adopting a 120t converter, drawing carbon and tapping to ensure that phosphorus in steel is less than 0.01 percent; controlling the end point carbon of the converter to be 0.15-0.40% and controlling the temperature to be 1590-1620 ℃; slag stopping and tapping, wherein the thickness of a slag layer is 0-30 mm; adding a deoxidizer in the process of smelting molten steel and tapping in a converter, wherein the deoxidizer contains 72-73% of Si, 11-12% of Ca, 11-12% of Ba, 1-2% of SiC and the balance of Fe + Al + impurity elements in percentage by mass, and the adding amount of the deoxidizer is 1.5-2.2 kg/t of molten steel;

(3) refining in an LF furnace, controlling the flow of bottom blown argon at 150-180 NL/min after the bottom blown argon is blown for 4-5 min, deoxidizing and refining by using calcium carbide for 5-10min, then adding ferrovanadium and ferrochrome for alloying for 3-5min, adjusting the flow of argon at 180-200 NL/min to promote the dissolution and absorption of alloy elements, and then adding ferronickel and ferrocopper for alloying for 3-5 min; then feeding 2m of calcium-silicon wire per ton of steel and rare earth, adjusting the flow of argon to be 50-120 NL/min, and blowing argon for 10-15 min to promote large-particle impurities to fully float upwards and then discharging the molten steel; the LF furnace adopts specific refining slag which consists of 48-50% of CaO, 225-28% of SiO, 8-15% of MgO, 78-10% of Al2O 35, 25-10% of CaF and less than or equal to 1.5% of FeO in percentage by mass;

(4) VD treatment, wherein the deep vacuum degassing time is more than or equal to 15min, the vacuum degree is not more than 0.08KPa, the argon blowing flow is 250-280 NL/min, and the soft blowing time after vacuum degassing is more than or equal to 18 min;

the tensile strength of the steel manufactured by the conventional rolling method in the field is more than or equal to 1180MPa, the elongation A after fracture is more than or equal to 12 percent, the pearlite inter-lamellar spacing is less than or equal to 0.17 micrometer, and the hardness is 400-430 HB.

Comparative examples 8 to 10

The parameters and effects of the above example 7 and comparative examples 8 to 10 are shown in the following table 3:

the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.