CN110923389B - Method for smelting low-carbon stainless steel by utilizing GOR converter - Google Patents

Abstract

The invention discloses a method for smelting low-carbon stainless steel by utilizing a GOR converter, which is characterized in that eight bottom guns are used in the GOR converter and are symmetrically distributed on the bottom of the converter in a groined shape and basically coincide with an impact area for blowing oxygen by a top gun, so that the bottom blowing flow is increased, the uniform mixing efficiency of a molten pool is improved, and the problem that airflow breaks through the molten pool due to overlarge bottom blowing flow is solved by utilizing the impact of blowing oxygen by the top gun, and the strong decarburization capability is realized; then, reasonable oxygen, argon/nitrogen proportion and flow distribution are adopted in the decarburization stage, oxygen and nitrogen (or argon) mixed in a certain proportion are blown in by bottom blowing in the dynamic decarburization stage, the partial pressure of CO in a molten pool is controlled, C in the molten pool is oxidized preferentially to Cr, the decarburization efficiency is improved, the oxidation of Cr is reduced, C can reach about 0.010 percent or even lower at the GOR end point, and Cr in reduced slag can reach about 0.010 percent or even lower₂O₃The content is controlled within 2 percent, and the capability of economically and stably producing the medium-high chromium stainless steel with the C content of less than 0.030 percent by the GOR converter is realized.

Description

Method for smelting low-carbon stainless steel by utilizing GOR converter

Technical Field

The invention relates to a stainless steel smelting process, in particular to a method for smelting low-carbon stainless steel by utilizing a GOR converter.

Background

The existing low-carbon stainless steel smelting technology mainly comprises the following steps:

1) AOD furnace smelting method

The technology controls the proportion of oxygen and side-blown gas by side-blowing mixed gas, and controls the content of C in a stainless steel molten pool to be about 0.0100% by utilizing the strong gas supply capacity of AOD side-blowing, thereby realizing the purpose of producing the low-carbon stainless steel.

2) VOD vacuum method

The method comprises the steps of placing stainless steel crude steelmaking water in a steel ladle, placing the steel ladle in a vacuum tank, enabling the steel ladle to be in a relative vacuum state by using a vacuum pump, reducing CO partial pressure in the steel ladle by using vacuum, achieving the aim of decarbonization and chromium protection, and reducing C in a molten pool to be below 0.0060%.

3) Converter + RH method

The representative patent of the method is a method for manufacturing low-carbon stainless steel disclosed in Chinese patent No. CN201310171216. X. The method comprises the following steps in sequence: i, pretreating molten iron; II, smelting in a converter of K-OBM-S; III, primary LF ladle refining; IV, molten steel circulating vacuum decarburization: a) Heating the RH by using common steel; b) connecting a bottom argon blowing pipe and starting vacuumizing; c) reducing the vacuum pressure and blowing oxygen for decarburization, wherein the decarburization value is 0.025-0.035%; d) The vacuum value is reduced to 40mbar at the end of oxygen blowing; e) the carbon content reaches a target value of 0.025-0.035%, and reduction operation is carried out at an RH station: f) Fine adjustment is carried out, and the molten steel mass percentage after fine adjustment reaches the specified requirement and is discharged. The method for manufacturing the low-carbon stainless steel has high decarburization efficiency, and can decarburize finished products to 0.03 percent.

The three methods for producing the low-carbon stainless steel are common methods at present, wherein the side-blown flow of the AOD causes serious erosion to the refractory material of the furnace lining, the furnace age is generally not higher and is generally between 90 and 150 furnaces, and the refractory material cost is higher; both the VOD furnace and the RH furnace need to be smelted by using vacuum equipment, special equipment needs to be built, and an electric furnace, an AOD (argon oxygen decarburization) furnace or a converter is also needed to be used as a rough smelting furnace to produce rough steelmaking water for producing the low-carbon stainless steel, so that the production flow is long, the cost is high, but the method has higher advantage in smelting the ultra-low-carbon stainless steel (the content of C is less than 0.015 percent), and is generally mainly used for producing the ultra-low-carbon stainless steel. And the method has no advantages of efficiency and cost for producing the low-carbon stainless steel with the C content of more than 0.015% and less than 0.030%.

Besides the three mainstream smelting methods of the low-carbon stainless steel, the GOR converter can also be used for smelting the low-carbon stainless steel. The GOR converter is a bottom blowing converter with a top lance, and the GOR converter method is a technology for smelting stainless steel by using bottom blowing oxygen-nitrogen-argon mixed gas. Utilize GOR converter bottom blowing mode have other with AOD's side-blown mode, GOR converter bottom blowing rifle sets up 3 to 5 usually, be limited in the molten bath degree of depth on the flow, for preventing that the bottom blowing flow is too big, lead to the molten bath to puncture and can not reach good kinetic condition, lead to smelting effect to reduce, and take place the oxidation of a large amount of Cr when the low carbon district decarbonization, the alloy is received the yield and is low, and is with high costs, simultaneously because of needing more ferrosilicon to throw and add and reduce and lead to the recarburization, can not produce low carbon stainless steel steadily, with low costs. Therefore, it is generally used only for producing stainless steel with a carbon content of more than 0.030%, and is more difficult to produce particularly when the Cr content of the stainless steel is more than 16%.

Disclosure of Invention

The invention aims to provide a method for smelting low-carbon stainless steel by utilizing a GOR converter.

The technical scheme for realizing the purpose of the invention is as follows: a method for smelting low-carbon stainless steel by utilizing a GOR converter comprises the following steps:

s1: adding stainless steel crude steelmaking water into a GOR furnace at the temperature of 1500-1550 ℃; the GOR furnace is characterized in that a top gun is arranged at the top of the GOR furnace, eight bottom guns are arranged at the bottom of the GOR furnace, a cross coordinate is set according to the distribution position of the eight bottom guns by taking the center point of the bottom of the furnace as a reference, four bottom guns are symmetrically arranged on two sides of an abscissa axis respectively, the four bottom guns on each side are arranged in an isosceles trapezoid shape, the bottom guns positioned at the lower bottom of the isosceles trapezoid are arranged close to the abscissa axis, two waists of the isosceles trapezoid are symmetrically arranged relative to the ordinate axis, and the eight bottom guns are arranged in a shape like a Chinese character 'jing' around the center point and basically;

s2: a first main decarburization stage: the top lance oxygen flow of the GOR furnace is 90-100 Nm³Min; the flow rate of bottom-blown oxygen is 80-90 Nm³A flow rate of bottom-blown nitrogen/argon is 5-10 Nm³Blowing in the stage that the decarburization oxygen supply amount is limited by reducing the carbon content in the molten pool to 1.0 +/-0.1%;

s3: a second stage of main decarburization: controlling the temperature of a molten pool to be 1620-1650 ℃, and controlling the ratio of blown oxygen to nitrogen/argon to be 3:1, and controlling the oxygen flow of a top lance of the GOR furnace to be 80-100 Nm³Min, bottom blowing oxygen flow rate of 40-50 Nm³/minConverting, and blowing nitrogen/argon bottom flow according to 40-50 Nm³Blowing at the stage of decarburization oxygen supply amount is limited by reducing the carbon content in the molten pool to 0.35 +/-0.03%;

s4: a first dynamic decarburization stage: stopping blowing with top lance oxygen, controlling the temperature of the molten pool to 1650-1680 ℃, controlling the ratio of oxygen blown in by bottom blowing to nitrogen/argon to be 1:2, and controlling the flow of bottom blowing oxygen to be 30-40 Nm³The flow rate of bottom-blown nitrogen/argon is 60-80 Nm/min³The blowing is carried out at the stage, and the decarburization oxygen supply amount is limited by reducing the carbon content in the molten pool to 0.11 +/-0.01 percent;

s5: and a second stage of dynamic decarburization: the top lance oxygen continues to stop converting, the temperature of the molten pool is controlled to be 1680-1700 ℃, the ratio of oxygen blown in by bottom blowing to nitrogen/argon is 1:3, and the flow of bottom blowing oxygen is controlled according to 20-25 Nm³The flow rate of bottom-blown nitrogen/argon is 60-75 Nm/min³The blowing is carried out at the stage, and the decarburization oxygen supply amount is limited by reducing the carbon content in the molten pool to 0.04 +/-0.01 percent;

s6: a third dynamic decarburization stage: the top lance oxygen continues to stop converting, the temperature of the molten pool is controlled to 1650-1680 ℃, the ratio of oxygen blown in by bottom blowing to nitrogen/argon is 1:5, and the flow of bottom blowing oxygen is 10-15 Nm³A flow rate of bottom-blown nitrogen/argon is 50-75 Nm³The blowing is carried out at the min, the oxygen supply amount in the stage is limited by reducing the carbon content in the molten pool to 0.010 +/-0.002 percent, and then the bottom lance stops blowing;

s7: reduction and desulfurization;

s8: tapping;

wherein, the oxygen supply amount in the decarburization process is according to the chemical equation: c + O = CO, specifically, oxygen supply amount = ((16/12) × C%)/oxygen utilization coefficient, which is an empirical value for each manufacturer.

According to the invention, the number of bottom guns in the GOR converter is increased and the positions of the bottom guns are reasonably arranged, eight bottom guns are symmetrically distributed on the bottom of the converter in a # -shape and basically coincide with an impact area of oxygen blowing of a top gun, so that the bottom blowing flow can be increased, the uniform mixing efficiency of a molten pool is improved, the problem that the molten pool is punctured by airflow due to overlarge bottom blowing flow can be suppressed by utilizing the impact of oxygen blowing of the top gun, and the oxygen supply intensity of GOR is improvedCreates a powerful condition with the bottom blowing stirring capability and realizes the strong decarburization capability; then, reasonable oxygen, argon/nitrogen proportion and flow distribution are adopted in the decarburization stage, oxygen and nitrogen (or argon) mixed in a certain proportion are blown in by bottom blowing in the dynamic decarburization stage, the partial pressure of CO in a molten pool is controlled, C in the molten pool is oxidized preferentially to Cr, the decarburization efficiency is improved, the oxidation of Cr is reduced, C can reach about 0.010 percent or even lower at the GOR end point, and Cr in reduced slag can reach about 0.010 percent or even lower₂O₃The content is controlled within 2 percent, the technical index of the AOD method is achieved, the furnace life level is superior to that of the AOD method, the capability of economically and stably producing medium-high chromium stainless steel with the C content of less than 0.030 percent is realized, and a new method for smelting and producing low-carbon stainless steel is developed for a top-bottom combined blowing GOR converter.

Drawings

FIG. 1 is a schematic view of the distribution of bottom guns on the bottom of a furnace according to the present invention; wherein the dotted lines indicate that the arrangement of the four bottom guns on each side is in the shape of an isosceles trapezoid.

Detailed Description

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in figure 1, eight bottom guns (11-18) are arranged at the top and bottom of the GOR furnace, cross coordinates are set up according to the distribution positions of the eight bottom guns by taking the center point of the furnace bottom as a reference, four bottom guns (11-14, 15-18) are symmetrically arranged on two sides of an abscissa axis respectively, the four bottom guns on each side are arranged in an isosceles trapezoid shape, the bottom guns (13, 14,15, 16) positioned at the bottom of the isosceles trapezoid are arranged close to the abscissa axis, two waists of the isosceles trapezoid are symmetrically arranged relative to the ordinate axis, and the eight bottom guns are arranged in a well shape around the center point and basically coincide with an oxygen blowing impact area of the top guns.

Taking a 90-ton GOR furnace as an example, the distribution positions of eight bottom guns are divided into four intervals according to a cross coordinate established by taking the center point of the furnace bottom as a reference, wherein four bottom guns are respectively arranged at positions which are 925mm away from the horizontal coordinate of a central line and 300mm away from the vertical coordinate, and four bottom guns are respectively arranged at positions which are 600mm away from the horizontal coordinate of the central line and 1025mm away from the vertical coordinate.

Example 1:

the number of the furnace is as follows: 1907-147

Steel grade: 304L

Example 1 weight of liquid steel in furnace for rough smelting stainless steel: 93.2 tons, composition (%) of molten steel in the crude stainless steel charged into the furnace is shown in the following table:

C	Si	Mn	P	S	Cr	Ni	Cu	N
									2.652	0.04	0.11	0.036	0.254	17.71	6.45	0.04	0.03

the GOR converter smelting decarburization process is as follows:

s1: adding stainless steel crude steelmaking water with the temperature of 1500 ℃ into a GOR furnace;

s2, first stage of main decarburization: top lance oxygen flow rate: 90Nm³Min; bottom blowing flow rate: oxygen 80Nm³Min, nitrogen 5Nm³Min; blowing time: 16min, and entering a second stage of main decarburization after the carbon content in the molten pool is reduced to 1.0%;

s3: a second stage of main decarburization: controlling the temperature of a molten pool to be 1620-1650 ℃, the ratio of oxygen and nitrogen gases blown in to be 3:1, and the oxygen blowing flow rate of a top lance: 90Nm³Min; bottom blowing flow rate: oxygen 45Nm³Min, nitrogen 45Nm³Min, converting time: 13min, until the carbon content in the molten pool is reduced to 0.35%;

s4: a first dynamic decarburization stage: stopping blowing of top lance oxygen, controlling the temperature of a molten pool to 1650-1680 ℃, controlling the ratio of oxygen and nitrogen gases blown in by bottom blowing to be 1:2, and controlling the flow rate of bottom blowing oxygen to be 30Nm³Min, bottom-blown nitrogen/argon flow 60Nm³The blowing is carried out, and the decarburization oxygen supply amount is reduced to 0.10 percent by the carbon content in the molten pool;

s5: and a second stage of dynamic decarburization: the top lance oxygen continues to stop converting, the temperature of the molten pool is controlled to be 1680-1700 ℃, the oxygen-nitrogen gas ratio of bottom blowing oxygen is 1:3, and the flow rate of bottom blowing oxygen is 25Nm³Min, bottom-blown nitrogen/argon flow at 75Nm³The blowing is carried out, and the decarburization oxygen supply amount is reduced to 0.05 percent by the carbon content in the molten pool;

s6: a third dynamic decarburization stage: the top lance oxygen continues to stop converting, the temperature of the molten pool is controlled to 1650-1680 ℃, the ratio of oxygen and nitrogen gases blown in by bottom blowing is 1:5, and the flow rate of the bottom blowing oxygen is 12Nm³Min, bottom-blown nitrogen/argon flow 60Nm³Blowing for min;

s7: stopping blowing by a bottom lance when the carbon content of decarburization oxygen supply in a molten pool is reduced to 0.01 percent by calculation, and then carrying out reduction desulfurization; adding 3100kg of low-carbon low-aluminum ferrosilicon and 1000kg of lime according to calculation; 500kg of fluorite. Bottom blowing nitrogen is adopted, stirring is carried out for 8min, desulfurization reduction is carried out, and steel is tapped after the temperature and the components are qualified;

s8: tapping;

the steel tapping composition (%) of example 1 is shown in the following table:

C	Si	Mn	P	S	Cr	Ni	Cu	N
									0.019	0.54	1.33	0.034	0.002	18.24	7.97	0.05	0.034

example 2

The number of the furnace is as follows: 1907-148

Steel grade: 304L

Example 2 weight of molten steel of charged rough stainless steel 91.6 ton, the composition (%) of the molten steel of charged rough stainless steel is shown in the following table:

C	Si	Mn	P	S	Cr	Ni	Cu	N
									3.00	0.23	0.14	0.034	0.257	17.55	6.47	0.04	0.023

tapping composition (%) of example 2

C	Si	Mn	P	S	Cr	Ni	Cu	N
									0.023	0.51	1.45	0.033	0.003	18.28	7.96	0.05	0.047

Example 3:

the number of the furnace is as follows: 1907-186

Steel grade: 316L

Example 3 the weight of molten steel in the furnace-charged raw stainless steel was 92.2 tons, and the composition (%) of the molten steel in the furnace-charged raw stainless steel is shown in the following table:

C	Si	Mn	P	S	Cr	Ni	Cu	N
									1.70	0.37	0.16	0.033	0.277	16.23	6.70	0.05	0.027

the steel tapping composition (%) of example 3 is shown in the following table:

C	Si	Mn	P	S	Cr	Ni	Cu	N	Mo
										0.021	0.52	1.43	0.034	0.004	16.23	10.15	0.07	0.030	2.038

the GOR converter smelting decarburization process of examples 2-3 is different from that of example 1 in the parameters of each step, and the specific parameters are shown in Table 1.

Table 1:

the oxygen supply amount in the decarburization process of the invention is as follows: c + O = CO, specifically, oxygen supply amount = ((16/12) × C%)/oxygen utilization coefficient, which is an empirical value for each manufacturer; the reduction desulfurization step is prior art and will not be described herein.

In the dynamic decarburization stage, because the carbon in the molten pool is already low, the decarburization reaction is not as violent as in a high carbon area, and the decarburization requirement of the molten pool can be met only by utilizing the flow of bottom blowing oxygen supply, so that the top lance oxygen blowing is stopped; in the dynamic decarburization stage, oxygen and nitrogen (or argon) are blown in by bottom blowing in a certain proportion, the partial pressure of CO in the molten pool is controlled, so that C in the molten pool is oxidized preferentially to Cr, the gas dosage in the process needs to be controlled within a reasonable range, if too much oxygen increases the excessive oxidation loss of beneficial element Cr in the molten pool, the process is not economical, and if too low oxygen greatly prolongs the blowing time.

The invention breaks through the technical bottleneck that the traditional GOR furnace can cause overlarge bottom blowing flow due to the increase of bottom guns, so that a molten pool can be punctured, the eight bottom guns are arranged in a cross shape around the central point and basically coincide with the impact area of top gun oxygen blowing, so that the bottom blowing flow can be increased, the impact of the top gun oxygen blowing can be utilized to suppress airflow generated by overlarge bottom blowing flow, powerful conditions are created for improving the oxygen supply intensity and the bottom blowing stirring capacity of GOR, and the strong decarburization capacity is realized; meanwhile, in the decarburization process, according to a certain proportion and blowing flow, the temperature of the molten pool in different carbon content stages is controlled to achieve rapid decarburization, the Cr element in the molten pool is oxidized as little as possible, a stainless steel product with the carbon content lower than 0.03 percent and the medium-high chromium content is obtained economically and efficiently, the total oxygen blowing time can be controlled within 60 minutes, and the Cr in the reduced slag can be controlled within 60 minutes₂O₃The content is controlled within 2 percent, the technical index of the AOD method is achieved, and the furnace life level is superior to that of the AOD method.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent flow transformations made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (1)

1. A method for smelting low-carbon stainless steel by utilizing a GOR converter is characterized by comprising the following steps: which comprises the following steps:

s1: adding stainless steel crude steelmaking water into a GOR furnace at the temperature of 1500-1550 ℃; the GOR furnace is characterized in that a top gun is arranged at the top of the GOR furnace, eight bottom guns are arranged at the bottom of the GOR furnace, a cross coordinate is set according to the distribution position of the eight bottom guns by taking the center point of the bottom of the furnace as a reference, four bottom guns are symmetrically arranged on two sides of an abscissa axis respectively, the four bottom guns on each side are arranged in an isosceles trapezoid shape, the bottom guns positioned at the lower bottom of the isosceles trapezoid are arranged close to the abscissa axis, two waists of the isosceles trapezoid are symmetrically arranged relative to the ordinate axis, and the eight bottom guns are arranged in a shape like a Chinese character 'jing' around the center point and basically;

s2: a first main decarburization stage: the top lance oxygen flow of the GOR furnace is 90-100 Nm³Min; the flow rate of bottom-blown oxygen is 80-90 Nm³A flow rate of bottom-blown nitrogen/argon is 5-10 Nm³Blowing in the stage that the decarburization oxygen supply amount is limited by reducing the carbon content in the molten pool to 1.0 +/-0.1%;

s3: a second stage of main decarburization: controlling the temperature of a molten pool to be 1620-1650 ℃, and controlling the ratio of blown oxygen to nitrogen/argon to be 3:1, and controlling the oxygen flow of a top lance of the GOR furnace to be 80-100 Nm³Min, bottom blowing oxygen flow rate of 40-50 Nm³Blowing at min, and blowing nitrogen/argon from bottom at 40-50 Nm³Blowing in the stage that the decarburization oxygen supply amount is limited by reducing the carbon content in the molten pool to 0.35 +/-0.03%;

s4: a first dynamic decarburization stage: stopping blowing of top lance oxygen, controlling the temperature of a molten pool at 1650-1680 ℃, and controlling the ratio of oxygen blown in by bottom blowing to nitrogen/argonUnder the condition of 1:2, the flow rate of bottom blowing oxygen is 30-40 Nm³The flow rate of bottom-blown nitrogen/argon is 60-80 Nm/min³Blowing in the stage that the decarburization oxygen supply amount is limited by reducing the carbon content in the molten pool to 0.11 +/-0.01%;

s5: and a second stage of dynamic decarburization: the top lance oxygen continues to stop converting, the temperature of the molten pool is controlled to be 1680-1700 ℃, the ratio of oxygen blown in by bottom blowing to nitrogen/argon is 1:3, and the flow of bottom blowing oxygen is controlled according to 20-25 Nm³The flow rate of bottom-blown nitrogen/argon is 60-75 Nm/min³The blowing is carried out at the stage, and the decarburization oxygen supply amount is limited by reducing the carbon content in the molten pool to 0.04 +/-0.01 percent;

s6: a third dynamic decarburization stage: the top lance oxygen continues to stop converting, the temperature of the molten pool is controlled to 1650-1680 ℃, the ratio of oxygen blown in by bottom blowing to nitrogen/argon is 1:5, and the flow of bottom blowing oxygen is 10-15 Nm³A flow rate of bottom-blown nitrogen/argon is 50-75 Nm³The blowing is carried out at the min, the oxygen supply amount in the stage is limited by reducing the carbon content in the molten pool to 0.010 +/-0.002 percent, and then the bottom lance stops blowing;

s7: reduction and desulfurization;

s8: tapping;

wherein, the oxygen supply amount in the decarburization process is according to the chemical equation: c + O = CO, specifically, oxygen supply amount = ((16/12) × C%)/oxygen utilization coefficient.

Images