CN119061316A - Austenitic stainless steel with less slag generated during welding pipe making and preparation method thereof - Google Patents
Austenitic stainless steel with less slag generated during welding pipe making and preparation method thereof Download PDFInfo
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- CN119061316A CN119061316A CN202411523301.2A CN202411523301A CN119061316A CN 119061316 A CN119061316 A CN 119061316A CN 202411523301 A CN202411523301 A CN 202411523301A CN 119061316 A CN119061316 A CN 119061316A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/02—Dephosphorising or desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
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Abstract
本发明公开了焊接制管时焊渣生成量少的奥氏体不锈钢的制备方法，包括以下步骤：（1）将原料投入EAF炉进行熔融；出钢前预脱硫；（2）AOD炉精炼工序包括：吹氧脱碳→还原→出钢；其中：在还原工序中，采用低铝硅铁合金进行脱氧，低铝硅铁合金的投入量为20～35kg/吨，所述低铝硅铁合金中的硅含量为75～80%，所述低铝硅铁合金中的铝含量在0.5%以下；在整个AOD精炼过程中，将精炼渣的碱度控制在1.7±0.1；在出钢工序中，出钢温度控制在1625±25°C；（3）将AOD炉精炼后的钢水倒入白云石钢包；（4）连铸：将白云石钢包中的钢水经中间包进入连铸机连铸。本发明具有焊接制管时焊渣生成量少的优点。
The invention discloses a method for preparing austenitic stainless steel with less slag generated during welding pipe making, comprising the following steps: (1) putting raw materials into an EAF furnace for melting; pre-desulfurization before tapping; (2) an AOD furnace refining process comprising: oxygen blowing decarburization→reduction→tapping; wherein: in the reduction process, a low aluminum silicon ferroalloy is used for deoxidation, the input amount of the low aluminum silicon ferroalloy is 20-35 kg/ton, the silicon content in the low aluminum silicon ferroalloy is 75-80%, and the aluminum content in the low aluminum silicon ferroalloy is below 0.5%; in the entire AOD refining process, the basicity of the refined slag is controlled at 1.7±0.1; in the tapping process, the tapping temperature is controlled at 1625±25°C; (3) pouring the molten steel refined in the AOD furnace into a dolomite ladle; (4) continuous casting: the molten steel in the dolomite ladle is continuously casted in a continuous casting machine through a tundish. The invention has the advantage of less slag generated during welding pipe making.
Description
Technical Field
The invention relates to the technical field of austenitic stainless steel, in particular to a preparation method of austenitic stainless steel with small welding slag generation amount during pipe welding.
Background
When the austenitic stainless steel is used for welding a pipe, an austenitic stainless steel strip with the thickness of less than 2.0mm is usually manufactured by adopting a self-fluxing argon arc welding (TIG) welding method, namely the TIG welding provides heat, welding wires are not added during welding, and welding seams are obtained only by melting and solidifying the butt joint parts of the stainless steel strips, so that the stainless steel strips are butt-jointed to form the welded pipe.
Welding slag is formed on the surface (inner/outer) of a welding seam in the welding process, and the welding slag occurs because inclusions in a material matrix are not easy to melt during welding, and the main components of the inclusions comprise MgAl 2O4、CaO、SiO2 and other unavoidable oxides, gather under the action of welding convection and float on the surface of the welding seam to form the welding slag. The welding slag can affect the quality of the welding seam, so that the welding seam is incomplete, the corrosion resistance is reduced due to the existence of local impurities, and under the condition of allowing polishing, the thickness of the pipe wall of the welded pipe can be reduced to be below the nominal thickness after the welding slag is completely polished, so that the quality of the finished product of the welded pipe is affected. The occurrence of slag during welding should be minimized.
Currently, the invention patent of CN102308012a discloses a "ferritic stainless steel with less black spot generation", in which the reduction of the black spot generation amount is achieved by controlling bi=3al+ti+0.5si+200ca.ltoreq.0.8, but the conventional grade 304, 316 stainless steel does not contain Ti element, and thus has a limitation in application of austenitic stainless steel.
Disclosure of Invention
It is a first object of the present invention to provide austenitic stainless steel with a small amount of slag formation when welding a pipe.
The austenitic stainless steel is characterized in that the composition of inclusions in the austenitic stainless steel comprises 32.0-66.0% of MgAl 2O4：8.0～31.0%,CaO：9.5～38.0%,SiO2 and the balance of other unavoidable oxides, and the sum of the components of MgAl 2O4、CaO、SiO2 is 82-95% of the total number of inclusion components.
A second object of the present invention is to provide a method for producing austenitic stainless steel with a small amount of slag formation when welding a pipe.
In order to achieve the aim, the invention adopts the following technical scheme that the preparation method of the austenitic stainless steel with small welding slag generation amount during pipe making welding comprises the following steps:
(1) Pre-desulfurizing the molten steel before tapping, and controlling the sulfur content in the molten steel to be below 0.05%;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
in the reduction process, deoxidizing by adopting a low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 20-35 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 75-80%, and the aluminum content in the low-aluminum ferrosilicon alloy is below 0.5%;
In the whole AOD refining process, controlling the alkalinity of refining slag to be 1.7+/-0.1;
in the tapping process, the tapping temperature is controlled to be 1625+/-25 ℃;
(3) Pouring molten steel refined by an AOD furnace into a dolomite ladle, wherein a refractory layer in the dolomite ladle, which is in contact with molten steel, is made of a dolomite material;
(4) The method comprises the steps of continuously casting molten steel in a dolomite ladle into a continuous casting machine through a tundish to form austenitic stainless steel, wherein the components of inclusions in the austenitic stainless steel comprise 32.0-66.0% of MgAl 2O4：8.0～31.0%,CaO：9.5～38.0%,SiO2 and the balance of other unavoidable oxides, the sum of the components of MgAl 2O4、CaO、SiO2 is 82-95% of the total number of inclusion components, and before the molten steel is put into the tundish, air in the tundish is exhausted by using protective gas, and the protective gas is always introduced into the tundish in the whole continuous casting process.
Further, in the method for producing austenitic stainless steel with a small amount of slag formation during pipe making by welding, in the step (1), lime is added to molten steel to pre-desulfurize the molten steel.
Further, in the method for producing austenitic stainless steel with a small amount of slag formation in welding pipe production, in the step (2), when deoxidizing is performed using a low-aluminum ferrosilicon alloy in which the silicon content is 78% and the aluminum content is 0.5% or less in the reduction step, the amount of the low-aluminum ferrosilicon alloy to be charged is 30 kg/ton.
Further, in the above-mentioned method for producing austenitic stainless steel with a small amount of slag formation in welding pipe production, in step (2), the basicity of the refining slag is controlled to 1.7 throughout the AOD refining process.
Further, in the above method for producing austenitic stainless steel with a small amount of slag formation in welding pipe production, in step (2), the tapping temperature is controlled at 1625 ℃ in the tapping step.
In the method for preparing austenitic stainless steel with small slag formation during pipe making by welding, argon is selected as the shielding gas in the step (4).
Through implementation of the technical scheme, the invention has the beneficial effects that the main component composition of the inclusions in the austenitic stainless steel in the steelmaking process is controlled through the smelting process, and the melting point of the inclusions is effectively reduced through controlling the component compositions of the main components MgAl 2O4、CaO、SiO2 of the inclusions.
Drawings
Fig. 1 is a schematic structural view of a dolomite ladle.
Fig. 2 is a schematic structural diagram of a tundish.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent.
The austenitic stainless steel with small welding slag generation amount during pipe making is welded, wherein the composition of inclusions in the austenitic stainless steel comprises 32.0-66.0% of MgAl 2O4：8.0～31.0%,CaO：9.5～38.0%,SiO2 and the balance of other unavoidable oxides, and the total composition of the three components of MgAl 2O4、CaO、SiO2 accounts for 82-95% of the total composition of the inclusions; the melting point of the inclusion is controlled by controlling the composition ratio of the three main components of MgAl 2O4、CaO、SiO2 in the inclusion, and when the composition ratio of the three main components of MgAl 2O4、CaO、SiO2 in the inclusion meets the conditions, the melting point of the inclusion is low, so that the inclusion is easy to melt and become liquid during welding, and the inclusion is prevented from gathering and floating on the surface of a welding line to form welding slag during welding, thereby effectively reducing the generation of the welding slag.
As shown in fig. 1 and 2, the method for producing austenitic stainless steel with a small amount of slag formation during welding of a pipe comprises the steps of:
(1) The method comprises the steps of feeding raw materials into an EAF furnace to melt to form molten steel, pre-desulfurizing the molten steel by feeding lime into the molten steel before tapping, and controlling the sulfur content in the molten steel to be below 0.05 percent;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
in the reduction process, deoxidizing by adopting a low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 20-35 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 75-80%, and the aluminum content in the low-aluminum ferrosilicon alloy is below 0.5%;
In the whole AOD refining process, controlling the alkalinity of refining slag to be 1.7+/-0.1;
in the tapping process, the tapping temperature is controlled to be 1625+/-25 ℃, and the low tapping temperature can reduce the reaction degree of Mg, al and oxygen in molten steel, so that the reaction of Mg, al and oxygen in molten steel to generate MgAl 2O4 and the generation of inclusion MgAl 2O4 in the process of entering a dolomite ladle;
(3) The structure of the dolomite ladle comprises a ladle body 1 with an open top and closed sides, wherein the inner wall of the ladle body 1 is covered with a layer of dolomite refractory layer 2 made of dolomite, and the dolomite refractory layer 2 in contact with the steel water in the dolomite ladle is free of aluminum, so that the reaction between the refractory layer and the steel water can be avoided, the increase of aluminum content in the steel water is prevented, and the generation of MgAl 2O4 in inclusions is further reduced;
(4) Continuously casting molten steel in a dolomite ladle into a continuous casting machine through a tundish to form austenitic stainless steel, wherein the composition of inclusions in the austenitic stainless steel comprises 32.0-66.0% of MgAl 2O4：8.0～31.0%,CaO：9.5～38.0%,SiO2 and the balance of other unavoidable oxides, and the total composition of the MgAl 2O4、CaO、SiO2 accounts for 82-95% of the total composition of the inclusions;
before molten steel is put into a tundish, air in the tundish is exhausted by using shielding gas, and in the whole continuous casting process, shielding gas is always introduced into the tundish, as shown in fig. 2, the structure of the tundish comprises a tundish body 3 and a ladle cover 4, the top of the tundish body 3 is open, a discharge hole 5 is arranged at the bottom of the tundish body 3, the ladle cover 4 is arranged at the top open of the tundish body 3, a feed inlet 6 and a shielding gas inlet 7 are arranged on the ladle cover 4, argon is firstly introduced into the tundish through the shielding gas inlet 7 before molten steel is put into the tundish, air in the tundish is exhausted, and in the whole continuous casting process, argon is always introduced into the tundish through the shielding gas inlet 7, so that an argon protection layer 9 formed by argon is always formed between the liquid surface of the molten steel 8 in the tundish and the ladle cover 4, the outside air is isolated by the argon protection layer 9, the invasion of oxygen is prevented, mgAl 2O4 is avoided by the reaction of Mg, al and oxygen, so that MgAl inclusion is generated, and the MgAl inclusion is further reduced, and the floating slag is formed on the surface of the invention, and the welding slag is effectively reduced when the MgAl is controlled, and the welding slag is formed, and the welding slag is effectively reduced.
Example 1
The preparation method of austenitic stainless steel with small welding slag generation amount during pipe welding comprises the following steps:
(1) The method comprises the steps of feeding raw materials into an EAF furnace to melt to form molten steel, and feeding lime into the molten steel to pre-desulphurize the molten steel before tapping, wherein the sulfur content in the molten steel is 0.023%;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
In the reduction procedure, deoxidizing by adopting low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 30 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 78%, and the aluminum content in the low-aluminum ferrosilicon alloy is 0.25%;
In the whole AOD refining process, the alkalinity of the refining slag is 1.7;
in the tapping process, the tapping temperature is 1625 ℃;
(3) Pouring molten steel refined by an AOD furnace into a dolomite ladle, wherein a refractory layer in the dolomite ladle, which is in contact with molten steel, is made of a dolomite material;
(4) The continuous casting is carried out, namely, molten steel in a dolomite ladle is fed into a continuous casting machine through a tundish to be continuously cast to form austenitic stainless steel, wherein the components of inclusions in the austenitic stainless steel comprise 34.8-53.8% of MgAl 2O4：11.6~31%,CaO：9.9~38%,SiO2 and the balance of other unavoidable oxides, the sum of the components of MgAl 2O4、CaO、SiO2 is 82-95% of the total number of inclusion components, and before the molten steel is fed into the tundish, argon is firstly used for exhausting air in the tundish, and argon is always introduced into the tundish in the whole continuous casting process.
Example 2
The preparation method of austenitic stainless steel with small welding slag generation amount during pipe welding comprises the following steps:
(1) The method comprises the steps of feeding raw materials into an EAF furnace to melt to form molten steel, and feeding lime into the molten steel to pre-desulphurize the molten steel before tapping, wherein the sulfur content in the molten steel is 0.048%;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
In the reduction procedure, deoxidizing by adopting a low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 20 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 75%, and the aluminum content in the low-aluminum ferrosilicon alloy is 0.49%;
In the whole AOD refining process, the alkalinity of the refining slag is 1.6;
In the tapping process, the tapping temperature is 1639 ℃;
(3) Pouring molten steel refined by an AOD furnace into a dolomite ladle, wherein a refractory layer in the dolomite ladle, which is in contact with molten steel, is made of a dolomite material;
(4) The method comprises the steps of continuously casting molten steel in a dolomite ladle into a continuous casting machine through a tundish to form austenitic stainless steel, wherein the components of inclusions in the austenitic stainless steel comprise 32-57.3% of MgAl 2O4：14.0~28.4%,CaO：19.1~35.4%,SiO2 and the balance of other unavoidable oxides, the sum of the components of MgAl 2O4、CaO、SiO2 is 82-95% of the total number of inclusion components, and before the molten steel is put into the tundish, the air in the tundish is exhausted by argon, and argon is always introduced into the tundish in the whole continuous casting process.
Example 3
The preparation method of austenitic stainless steel with small welding slag generation amount during pipe welding comprises the following steps:
(1) The method comprises the steps of feeding raw materials into an EAF furnace to melt to form molten steel, and feeding lime into the molten steel to pre-desulphurize the molten steel before tapping, wherein the sulfur content in the molten steel is 0.042%;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
In the reduction procedure, deoxidizing by adopting a low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 35 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 80%, and the aluminum content in the low-aluminum ferrosilicon alloy is 0.36%;
In the whole AOD refining process, the alkalinity of the refining slag is 1.67;
in the tapping process, the tapping temperature is 1650 ℃;
(3) Pouring molten steel refined by an AOD furnace into a dolomite ladle, wherein a refractory layer in the dolomite ladle, which is in contact with molten steel, is made of a dolomite material;
(4) The continuous casting is carried out, namely, molten steel in a dolomite ladle is fed into a continuous casting machine through a tundish to be continuously cast to form austenitic stainless steel, wherein the components of inclusions in the austenitic stainless steel comprise, by weight, 42.2-56.1% of MgAl 2O4：8~29.8%,CaO：9.5~26.9%,SiO2 and the balance of other unavoidable oxides, the sum of the components of MgAl 2O4、CaO、SiO2 is 82-95% of the total number of inclusion components, and before the molten steel is fed into the tundish, argon is firstly used for exhausting air in the tundish, and argon is always introduced into the tundish in the whole continuous casting process.
Example 4
The preparation method of austenitic stainless steel with small welding slag generation amount during pipe welding comprises the following steps:
(1) The method comprises the steps of feeding raw materials into an EAF furnace to melt to form molten steel, and feeding lime into the molten steel to pre-desulphurize the molten steel before tapping, wherein the sulfur content in the molten steel is 0.028%;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
in the reduction procedure, deoxidizing by adopting a low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 26 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 77%, and the aluminum content in the low-aluminum ferrosilicon alloy is 0.13%;
in the whole AOD refining process, the alkalinity of the refining slag is 1.8;
in the tapping process, the tapping temperature is 1600 ℃;
(3) Pouring molten steel refined by an AOD furnace into a dolomite ladle, wherein a refractory layer in the dolomite ladle, which is in contact with molten steel, is made of a dolomite material;
(4) The method comprises the steps of continuously casting molten steel in a dolomite ladle into a continuous casting machine through a tundish to form austenitic stainless steel, wherein the components of inclusions in the austenitic stainless steel comprise 45.3-66% of MgAl 2O4：12.4~29.4%,CaO：10.5~26.5%,SiO2 and the balance of other unavoidable oxides, the sum of the components of MgAl 2O4、CaO、SiO2 is 82-95% of the total number of inclusion components, and before the molten steel is put into the tundish, the air in the tundish is exhausted by argon, and argon is always introduced into the tundish in the whole continuous casting process.
Comparative example 1
The preparation method of austenitic stainless steel with small welding slag generation amount during pipe welding comprises the following steps:
(1) The method comprises the steps of feeding raw materials into an EAF furnace to melt to form molten steel, and feeding lime into the molten steel to pre-desulphurize the molten steel before tapping, wherein the sulfur content in the molten steel is 0.056%;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
In the reduction procedure, deoxidizing by adopting low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 18 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 72%, and the aluminum content in the low-aluminum ferrosilicon alloy is 0.65%;
in the whole AOD refining process, the alkalinity of the refining slag is 1.89;
In the tapping process, the tapping temperature is 1688 ℃;
(3) Pouring molten steel refined by an AOD furnace into a dolomite ladle, wherein a refractory layer in the dolomite ladle, which is in contact with molten steel, is made of a dolomite material;
(4) The continuous casting is that molten steel in a dolomite ladle enters a continuous casting machine through a tundish to be continuously cast to form austenitic stainless steel, wherein the components of inclusions in the austenitic stainless steel comprise 3.0-25.0% of MgAl 2O4：30.9~79.8%,CaO：0.5~31.5%,SiO2 and the balance of other unavoidable oxides, and before the molten steel is put into the tundish, argon is firstly used for exhausting air in the tundish, and argon is always introduced into the tundish in the whole continuous casting process.
Comparative example 2
The preparation method of austenitic stainless steel with small welding slag generation amount during pipe welding comprises the following steps:
(1) The method comprises the steps of feeding raw materials into an EAF furnace to melt to form molten steel, and feeding lime into the molten steel to pre-desulphurize the molten steel before tapping, wherein the sulfur content in the molten steel is 0.11%;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
In the reduction procedure, deoxidizing by adopting a low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 37 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 72%, and the aluminum content in the low-aluminum ferrosilicon alloy is 1.3%;
in the whole AOD refining process, the alkalinity of the refining slag is 2.2;
in the tapping process, the tapping temperature is 1702 ℃;
(3) Pouring molten steel refined by an AOD furnace into a dolomite ladle, wherein a refractory layer in the dolomite ladle, which is in contact with molten steel, is made of a dolomite material;
(4) And continuously casting molten steel in the dolomite steel ladle into a continuous casting machine through a tundish to form austenitic stainless steel, wherein the austenitic stainless steel comprises 13.2-26.4% of MgAl 2O4：7.5~27.8%,CaO：36.6~64.6%,SiO2 and the balance of other unavoidable oxides, wherein before the molten steel is put into the tundish, argon is firstly used for exhausting air in the tundish, and argon is always introduced into the tundish in the whole continuous casting process.
Comparative example 3
The preparation method of austenitic stainless steel with small welding slag generation amount during pipe welding comprises the following steps:
(1) The method comprises the steps of feeding raw materials into an EAF furnace to melt to form molten steel, and feeding lime into the molten steel to pre-desulphurize the molten steel before tapping, wherein the sulfur content in the molten steel is 0.098%;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
in the reduction procedure, deoxidizing by adopting a low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 16 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 72%, and the aluminum content in the low-aluminum ferrosilicon alloy is 0.68%;
In the whole AOD refining process, controlling the alkalinity of refining slag to be 2.1;
In the tapping process, the tapping temperature is 1695 ℃;
(3) Pouring molten steel refined by an AOD furnace into a dolomite ladle, wherein a refractory layer in the dolomite ladle, which is in contact with molten steel, is made of a dolomite material;
(4) The continuous casting is that molten steel in a dolomite ladle enters a continuous casting machine through a tundish to be continuously cast to form austenitic stainless steel, wherein the components of inclusions in the austenitic stainless steel comprise 70.4-78.5% of MgAl 2O4：4.7~20.9%,CaO：1.1~8.5%,SiO2 and the balance of other unavoidable oxides, and before the molten steel is put into the tundish, argon is firstly used for exhausting air in the tundish, and argon is always introduced into the tundish in the whole continuous casting process.
The method for measuring the inclusion components in each example and each comparative example in the present invention is a common technique, and specifically comprises sampling a slab after continuous casting, preparing a metallographic specimen with a bright surface by cutting, hot-inlaying, grinding and polishing, and then scanning and analyzing the inclusion components on the polished surface of the specimen by using an electronic probe (EPMA: electron Probe Microanalysis) device to obtain the inclusion components. The invention continuously collects and analyzes the inclusion components at a plurality of different positions of the slab sample by the electronic probe equipment, thereby obtaining the inclusion component range.
Since weld slag points are caused by the presence of high-melting-point inclusions when austenitic stainless steel is welded using argon arc welding (TIG), the evaluation of the slag formation amount can also indirectly reflect the melting point of inclusions in austenitic stainless steel (reference ：B.Pollard. The Effect of Minor Elements on the Welding Characteristics of Stainless Stee. Welding Research Supplement(1988), 202-s to 213-s.）. evaluates the effectiveness of inclusion control on the basis of the amount of slag points formed per 6 m of welded pipe as an evaluation basis).
Since the inclusion components at each position in the austenitic stainless steel cannot be consistent, the inclusion components of the austenitic stainless steel can only be represented by each inclusion component range when represented, the inclusion component ranges of each embodiment and comparative example of the invention are obtained by collecting and analyzing inclusion components of a plurality of points of the austenitic stainless steel through an electronic probe device, and because the actual collection points are numerous, each embodiment and each comparative example of the invention only select the impurity components collected by a plurality of points, the invention lists the impurity components collected by three to six points selected in embodiments 1-4 and comparative examples 1-3 and the corresponding welding slag generation amounts as follows:
As is clear from the data of the examples and the comparative examples, the main components of the inclusions in the austenitic stainless steel prepared in the examples 1-4 are controlled to be MgAl 2O4：8.0~31.0%,CaO：9.5~38.0%,SiO2:32.0-66.0%, the total content of MgAl 2O4、CaO、SiO2 is 82-95% of the total content of the inclusions, and the formation amount of welding slag points of each 6m welding pipe is 0 or 1 in the content range, so that the melting point of the inclusions in the austenitic stainless steel prepared in the examples 1-4 is indirectly reflected to be low;
and the yield of welding slag points of the austenitic stainless steel prepared in the comparative examples 1-3 is 6-12 per 6 m welding pipe, which is far higher than that of the austenitic stainless steel prepared in the examples 1-4, so that the melting point of inclusions in the austenitic stainless steel prepared in the comparative examples 1-3 is indirectly reflected to be high.
The invention has the advantages that the main component composition of the inclusion in the austenitic stainless steel in the steelmaking process is controlled by the smelting process, the main component composition MgAl 2O4、CaO、SiO2 of the inclusion is controlled to be MgAl 2O4：8.0~31.0%,CaO：9.5~38.0%,SiO2:32.0-66.0%, and the total component sum of the MgAl 2O4、CaO、SiO2 accounts for 82-95% of the total inclusion component, so that the melting point of the inclusion is effectively reduced, and the inclusion is easy to melt and liquid when the austenitic stainless steel is used for welding a pipe, so that the inclusion is not gathered and floats on the surface of a welding seam to form welding slag when the pipe is welded, and the welding slag generation amount when the pipe is welded is effectively reduced.
The above description is only of the preferred embodiment of the present invention, and is not intended to limit the present invention in any other way, but any modifications or equivalent variations according to the technical spirit of the present invention are still included in the scope of the present invention.
Claims (7)
1. The austenitic stainless steel with small welding slag generation amount during pipe making welding is characterized in that the composition of inclusions in the austenitic stainless steel comprises 32.0-66.0% of MgAl 2O4：8.0～31.0%,CaO：9.5～38.0%,SiO2 and the balance of other unavoidable oxides, and the total composition of the MgAl 2O4、CaO、SiO2 accounts for 82-95% of the total inclusion composition.
2. The preparation method of austenitic stainless steel with small welding slag generation amount during pipe making welding is characterized by comprising the following steps:
(1) Pre-desulfurizing the molten steel before tapping, and controlling the sulfur content in the molten steel to be below 0.05%;
(2) The molten steel after the primary smelting of the EAF furnace is put into an AOD furnace for refining, and the refining process of the AOD furnace comprises oxygen blowing and decarburization, reduction and tapping, wherein:
in the reduction process, deoxidizing by adopting a low-aluminum ferrosilicon alloy, wherein the input amount of the low-aluminum ferrosilicon alloy is 20-35 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 75-80%, and the aluminum content in the low-aluminum ferrosilicon alloy is below 0.5%;
In the whole AOD refining process, controlling the alkalinity of refining slag to be 1.7+/-0.1;
in the tapping process, the tapping temperature is controlled to be 1625+/-25 ℃;
(3) Pouring molten steel refined by an AOD furnace into a dolomite ladle, wherein a refractory layer in the dolomite ladle, which is in contact with molten steel, is made of a dolomite material;
(4) Continuously casting molten steel in a dolomite ladle into a continuous casting machine through a tundish, so as to form austenitic stainless steel, wherein the composition of inclusions in the austenitic stainless steel comprises 32.0-66.0% of MgAl 2O4：8.0～31.0%,CaO：9.5～38.0%,SiO2 and the balance of other unavoidable oxides, and the total sum of the components of MgAl 2O4、CaO、SiO2 is 82-95% of the total number of inclusion components;
Before molten steel is put into a tundish, air in the tundish is exhausted by using protective gas, and the protective gas is always introduced into the tundish in the whole continuous casting process.
3. The method for producing austenitic stainless steel with a small amount of slag formation when welding a pipe as set forth in claim 2, wherein in step (1), the molten steel is pre-desulfurized by adding lime to the molten steel.
4. The method for producing austenitic stainless steel with a small amount of slag generated when welding a pipe as set forth in claim 2, wherein in the step (2), the amount of low-aluminum ferrosilicon alloy added in deoxidization performed in the reduction step is 30 kg/ton, the silicon content in the low-aluminum ferrosilicon alloy is 78%, and the aluminum content in the low-aluminum ferrosilicon alloy is 0.5% or less.
5. The method for producing austenitic stainless steel with a small amount of slag formation when welding pipe production according to claim 2, wherein in step (2), the basicity of the refining slag is controlled to 1.7 throughout the AOD refining process.
6. The method for producing austenitic stainless steel with a small amount of slag formation when welding a pipe according to claim 2, wherein in step (2), the tapping temperature is controlled to 1625 ℃.
7. The method for producing austenitic stainless steel with a small amount of slag generated during welding of a pipe as set forth in claim 2, wherein in step (4), argon is used as the shielding gas.
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