CN102409133B - Method for producing 23MnB steel by adopting vacuum process - Google Patents
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Abstract
The invention discloses a method for producing 23MnB steel by adopting a vacuum process and belongs to the field of ferrous metallurgy. The invention aims at solving the technical problem of providing a method for producing 23MnB steel by smooth casting with a large-size continuous casting machine. The method comprises the following steps of: a, smelting in a converter; b, when steel tapping, adding calcium carbide in molten steel and then adding aluminum, so that the weight percentage content of acid-soluble aluminum in the molten steel is between 0.014% and 0.019%; c, refining in an LF (ladle furnace); d, after refining, carrying out vacuum circulation treatment, wherein in the treatment, aluminum is added into the molten steel so that the content of acid-soluble aluminum is 0.025-0.055%, titanium is added so that the content of titanium is 0.02-0.06%, and boron is added so that the content of boron is 0.0005-0.003%; and e, continuously casting. According to the invention, the content of acid-soluble aluminum is strictly controlled from various steps, the yield of boron is high, the hardenability of the 23MnB steel is good, and the water gap of the large-size continuous casting machine is prevented from being dwindled.
Description
Technical field
The invention belongs to the ferrous metallurgy field, be specifically related to a kind of method of producing 23 MnB steel by adopting vacuum process.
Background technology
Trace B (about 0.001%) can be adsorbed on austenite grain boundary, reduce the crystal boundary energy, prevent the ferrite nucleation, improve exponentially the hardening capacity of middle low carbon steel, so the trace B of the normal interpolation 0.0005～0.003% of middle low carbon steel improves the hardening capacity of steel.But boron is one of as lively as a cricket element, can with steel in residual oxygen and nitrogen form stable inclusion, and lose beneficial effect, the boron that only exists with the solid solution form just can play useful effect.
Existing studies show that, boron and oxygen and nitrogen all have very strong avidity, and boron is easy to oxidized generation B
6O or B
2O
3, perhaps generating BN with nitrification, these all are the objectionable impuritiess that stop boron performance raising hardening capacity effect in the boron-containing steel.Therefore, improve the effect of hardening capacity for guaranteeing boron, must in the smelting process of steel, at first adopt aluminium to slough the free oxygen of molten steel, and with the fixing nitrogen in the molten steel of titanium, the useful effect of guarantee adding boron.
The 23MnB steel is boracic class formation steel, be usually used in making the grip-pad that pitch is 216 following dozers or excavator, chemical composition is by weight percentage: C:0.20～0.0.27%, Mn:0.80～1.10%, Si:0.15～0.35%, P≤0.030%, S≤0.015%, Cr≤0.30%, Ni≤0.25%, Cu≤0.30%, B:0.0005～0.0035%.Generally for guaranteeing that boron improves the effect of hardening capacity, also require to contain aluminium and the titanium of certain mass.For example:
The patent CN100519769C that open day is on July 29th, 2009 discloses the method that a kind of converter smelting is produced boron-containing steel, it is characterized in that adopting the explained hereafter boron-containing steel of converter smelting → ladle deoxidation, refining → boron alloy, concrete operational provisions is: at first be to add aluminium and refining slag carries out deoxidation to molten steel and slag behind converter tapping, the molten aluminium of control molten steel acid is in 0.02%～0.04% scope, then the FeO+MnO in LF stove refining controlling slag≤2.0%, and the α of molten steel
[O]≤ 10ppm adds after aluminium carries out deep deoxidation to ladle at last again, adds ferrotianium and ferro-boron and carries out alloying.The recovery rate height that adopts this technique boron is 69.4%～91.8%.This patent improves the effect of hardening capacity in order to guarantee boron, adding aluminium and refining slag carry out deoxidation to molten steel and slag behind converter tapping, the molten aluminium of control molten steel acid is in 0.02%～0.04% scope, in molten steel, add aluminium again after the refining of LF stove is complete, guarantee the recovery rate of boron and the hardening capacity of boron-containing steel with this, but this patent is not considered and is added aluminium to the impact of continuous caster continuous casting.The applicant finds that aluminium can lose a part in the process of producing the 23MnB steel, wayward for the content of aluminium, has part aluminium can be oxidized to Al
2O
3, these Al
2O
3The conticaster crystallizer mouth of a river is diminished, and molten steel flow reduces, thereby affects continuous casting, brings very large difficulty for the control of continuous caster, and security incident is caused at the when serious even obstruction continuous caster mouth of a river.Therefore, now be badly in need of a kind of method of production boron-containing steel of strict control technique, the method can improve the recovery rate of boron, the hardening capacity of assurance boron-containing steel, can avoid the continuous caster mouth of a river to diminish, make continuous casting smooth simultaneously.
Summary of the invention
That technical problem to be solved by this invention provides is a kind of when guaranteeing boron-containing steel hardening capacity, avoid the method for the production 23MnB steel that the large specification continuous caster mouth of a river diminishes.
The technical solution adopted for the present invention to solve the technical problems is:
The method of producing 23 MnB steel by adopting vacuum process comprises the steps:
A, in converter, add molten iron smelting;
B, molten steel are tapped to ladle, in molten steel, add calcium carbide during tapping, it is foundation that the calcium carbide consumption just refines endpoint carbon content according to converter, when converter terminal carbon weight percent drops into by molten steel 3.5～4.5kg per ton when following 0.10%, when converter terminal carbon weight percent drops into by molten steel 2.5～3.5kg per ton greater than 0.10%, less than 0.15% the time, when converter terminal carbon weight percent 0.15% when above by molten steel 1.5～2.5kg input per ton; Add again aluminium, make the weight percent content of sour molten aluminium in the molten steel 0.014～0.019%;
C, ladle move into the refining of LF stove;
After d, the refining ladle is moved into the RH vacuum treatment installation and carry out the vacuum cycle processing, in molten steel, add aluminium in the processing, make in the molten steel sour molten aluminium weight percent content 0.025～0.055%, add again titanium and make in the molten steel titanium weight percent content 0.02～0.06%, add boron and make in the molten steel boron weight percent content 0.0005～0.003%;
E, vacuum cycle are carried out continuous casting after processing.
Wherein, in the aforesaid method steps d, in molten steel, add aluminium, make in the molten steel sour molten aluminium weight percent content 0.035～0.04%.
Wherein, also add steel scrap when adding molten iron in the converter among the aforesaid method step a, the weight of steel scrap can not surpass 15% of weight of molten iron.
Further, when just refining of molten steel composition to C by weight percentage is 0.05%～0.15%, in the ladle of molten steel being tapped when P≤0.030% and S≤0.015%.
Also add when wherein, adding calcium carbide among the aforesaid method step b ferrosilicon make in the molten steel silicon weight percent content 0.15～0.35%, add ferromanganese make in the molten steel manganese weight percent content 0.80%～1.10%, add carburelant and make the carbon weight percent content 0.20～0.27%.
Described carburelant mainly refer to contain fixed carbon more than 98% asphalt adhesive or contain the hard coal of fixed carbon more than 92%.
Wherein, among the aforesaid method step c, stopped heating when molten steel is heated to 1590～1610 ℃ moves into the RH vacuum treatment installation with ladle.
Wherein, pressure≤300Pa when aforesaid method steps d vacuum cycle is processed, 10～15 minutes treatment times.
Wherein, during aforesaid method step e continuous casting in the continuous caster bag temperature be 1535 ± 20 ℃.
Wherein, calcium carbide contains CaC described in the aforesaid method
2More than 70%.
The inventive method specifically can be implemented in the following manner: the method for producing 23 MnB steel by adopting vacuum process comprises the steps:
A, add molten iron and smelting in the converter, the weight of steel scrap can not surpass 15% of weight of molten iron, when just refining of molten steel composition to C by weight percentage is 0.05%～0.15%, in the ladle of molten steel being tapped when P≤0.030% and S≤0.015%;
B, molten steel are tapped to ladle, add in the molten steel during tapping and contain CaC
2Calcium carbide more than 70%, it is foundation that the calcium carbide consumption just refines endpoint carbon content according to converter, when converter terminal carbon weight percent drops into by molten steel 3.5～4.5kg per ton when following 0.10%, when converter terminal carbon weight percent drops into by molten steel 2.5～3.5kg per ton greater than 0.10%, less than 0.15% the time, when converter terminal carbon weight percent 0.15% when above by molten steel 1.5～2.5kg input per ton; Add again aluminium, make the weight percent content of sour molten aluminium in the molten steel 0.014～0.019%, also add when adding calcium carbide ferrosilicon make in the molten steel silicon weight percent content 0.15～0.35%, add ferromanganese make in the molten steel manganese weight percent content 0.80%～1.10%, add carburelant and make the carbon weight percent content 0.20～0.27%;
C, ladle move into the refining of LF stove, and stopped heating when molten steel is heated to 1590～1610 ℃ moves into the RH vacuum treatment installation with ladle;
After d, the refining ladle is moved into the RH vacuum treatment installation and carry out the vacuum cycle processing, in molten steel, add aluminium in the processing, make in the molten steel sour molten aluminium weight percent content 0.035～0.04%, adding titanium makes in the molten steel titanium weight percent content 0.02～0.06% again, adding boron makes in the molten steel boron weight percent content 0.0005～0.003%, pressure≤300Pa when vacuum cycle is processed, 10～15 minutes treatment times;
E, vacuum cycle are carried out continuous casting after processing, and wrapping temperature in the continuous caster during continuous casting is 1535 ± 20 ℃.
The invention has the beneficial effects as follows: the contriver finds that continuous caster mold gap in casting cycle diminishes even stops up, owing to aluminium too high levels in the molten steel causes, and therefore must the strict aluminum content of controlling in the molten steel.But in order to guarantee that boron in the boron-containing steel improves the effect of hardening capacity, boron-containing steel must at first adopt aluminium to slough the free oxygen of molten steel in the smelting process of steel usually, and with the fixing nitrogen in the molten steel of titanium, the useful effect of guarantee adding boron.Therefore, those skilled in the art have often ignored the impact of aluminium on the continuous caster continuous casting for the hardening capacity that guarantees boron-containing steel.Analyze boron-containing steel production key point in the prior art, add aluminium just in order to slough as much as possible the free oxygen in the molten steel, the tapping process of the inventive method after just refining of molten steel is complete adopts first calcium carbide to carry out pre-deoxidation, be generally again the relation of a constant according to carbon in the converter steelmaking process and equilibrium oxygen, the technology of the present invention has been taked according to the different end point carbons of converter, the way of the different calcium carbide quantity of corresponding adding is carried out pre-deoxidation, and then the further deoxidation of employing aluminium, make the weight percent content of sour molten aluminium in the molten steel between 0.014～0.019%, strict control adds the amount of aluminium.After the above-mentioned deoxidation of molten steel process, molten steel oxygen activity α
[O]Can be controlled in below 0.0015%.Ladle moves on to the LF refining furnace molten steel is carried out refining, after the refining ladle is moved into the RH vacuum treatment installation and carry out the vacuum cycle processing, in molten steel, add aluminium, make in the molten steel sour molten aluminium weight percent content 0.025～0.055%, preferred content is 0.035～0.04%.Controlling sour molten aluminium (Als) herein in 0.025～0.055% scope, is to consider that rear portion continuous casting steel machine process has the molten aluminium of part acid and is oxidized to Al
2O
3Phenomenon, learn that through a large amount of practices the continuous casting steel machine process has 0.005%～0.010% sour molten aluminium to be oxidized to Al
2O
3So, add aluminium and control sour molten aluminium in 0.025～0.055% scope, strictly control the scope of sour molten aluminium (Als), also have 0.02～0.05% sour molten aluminium with the molten steel that guarantees final casting, large specification continuous caster can be cast smoothly.Therefore, the present invention strictly controls sour molten aluminium (Als) content from each step, the free oxygen that has guaranteed molten steel is removed, the boron recovery rate is high, the 23MnB steel hardenability is good, and don't as for making the aluminium in the molten steel too high, avoids the continuous caster mouth of a river to diminish, thereby guarantee that large specification continuous caster casts smoothly, the inventive method is specially adapted to the above continuous caster of 200 * 200mm specification.
Embodiment
The specific embodiment of the invention is as follows:
The method of producing 23 MnB steel by adopting vacuum process comprises the steps:
A, in converter, add molten iron smelting;
B, molten steel are tapped to ladle, in molten steel, add calcium carbide during tapping, it is foundation that the calcium carbide consumption just refines endpoint carbon content according to converter, when converter terminal carbon weight percent drops into by molten steel 3.5～4.5kg per ton when following 0.10%, when converter terminal carbon weight percent drops into by molten steel 2.5～3.5kg per ton greater than 0.10%, less than 0.15% the time, when converter terminal carbon weight percent 0.15% when above by molten steel 1.5～2.5kg input per ton; Add again aluminium, make the weight percent content of sour molten aluminium in the molten steel 0.014～0.019%;
C, ladle move into the refining of LF stove;
After d, the refining ladle is moved into the RH vacuum treatment installation and carry out the vacuum cycle processing, in molten steel, add aluminium in the processing, make in the molten steel sour molten aluminium weight percent content 0.025～0.055%, add again titanium and make in the molten steel titanium weight percent content 0.02～0.06%, add boron and make in the molten steel boron weight percent content 0.0005～0.003%;
E, vacuum cycle are carried out continuous casting after processing.
The tapping process of the inventive method after just refining of molten steel is complete do not adopt aluminium to carry out pre-deoxidation, and the employing calcium carbide, be generally again the relation of a constant according to carbon in the converter steelmaking process and equilibrium oxygen, the technology of the present invention has been taked according to the different end point carbons of converter, the way of the different calcium carbide quantity of corresponding adding is carried out pre-deoxidation, can play the effect of deoxidation, can avoid again carbon to exceed standard, carbon is controlled in the suitable scope.The present invention strictly controls acid-soluble aluminum content from each step, has guaranteed that the free oxygen of molten steel is removed, and the boron recovery rate is high, and the 23MnB steel hardenability is good, and don't as for making the aluminium in the molten steel too high, thereby guarantees that large specification continuous caster casts smoothly.
Preferably, in the aforesaid method steps d, in molten steel, add aluminium, make in the molten steel sour molten aluminium weight percent content 0.035～0.04%.Controlling sour molten aluminium (Als) herein in 0.035～0.04% scope, is to consider that rear portion continuous casting steel machine process has the molten aluminium of part acid and is oxidized to Al
2O
3Phenomenon, learn that through a large amount of practices the continuous casting steel machine process has 0.005%～0.010% sour molten aluminium to be oxidized to Al
2O
3So the LF stove must add aluminium and control sour molten aluminium in 0.035～0.04% scope, strictly controls the scope of sour molten aluminium, also have 0.025～0.035% sour molten aluminium with the molten steel that guarantees final casting, large specification continuous caster can be cast smoothly.
Preferably, also add steel scrap when adding molten iron in the converter among the aforesaid method step a, the weight of steel scrap can not surpass 15% of weight of molten iron.Steel scrap can derive from salvage station, also can derive from steel mill inside.Converter steelmaking is originated without external heat, all rely on carbon in the oxidation molten iron, and a small amount of silicon and manganese emit heat, thereby make molten steel obtain heating, with respect to molten iron, the steel scrap carbon content is generally very low, and the steel scrap that adds in the converter smelting can play the effect that reduces temperature.Simultaneously in order to economize on resources, and produce qualified Finished Steel, because remaining Cr, Ni and Cu in the steel scrap are uncontrollable, can cause Cr＞0.30%, Ni＞0.25% in the molten steel, the phenomenon of Cu＞0.30% to occur for fear of excessive adding steel scrap, the weight of steel scrap can not surpass 15% of weight of molten iron.
Further, when just refining of molten steel composition to C by weight percentage is 0.05%～0.15%, in the ladle of molten steel being tapped when P≤0.030% and S≤0.015%.In fact steelmaking process is exactly initial oxidation, and then the process of reduction during converter steelmaking, is only carried out oxidizing reaction in converter, and reduction reaction is carried out in ladle.When C is 0.05%～0.15%, illustrate that oxidizing reaction is through with, should tap and carry out reduction reaction.
In order to produce qualified 23MnB steel, also add when adding calcium carbide among the aforesaid method step b ferrosilicon make in the molten steel silicon weight percent content 0.15～0.35%, add ferromanganese make in the molten steel manganese weight percent content 0.80%～1.10%, add carburelant and make the carbon weight percent content 0.20～0.27%.
Preferably, in order to guarantee that the bag temperature is 1535 ± 20 ℃ in the continuous caster, among the aforesaid method step c, stopped heating when molten steel is heated to 1590～1610 ℃ moves into the RH vacuum treatment installation with ladle.
Preferably, pressure≤300Pa when aforesaid method steps d vacuum cycle is processed, 10～15 minutes treatment times.To guarantee hydrogen richness≤0.0002%, avoid " white point " defective occurring after the steel billet cooling, " white point " is hydrogen pattern during macroscopic examination after the strand enrichment, if any the strand of " white point " defective, can form shank shape crackle through after rolling, causes strand to be scrapped.
Wherein, during aforesaid method step e continuous casting in the continuous caster bag temperature be 1535 ± 20 ℃.23MnB molten steel phase line temperature is 1505 ℃, and the superheating temperature of wrapping in the control continuous caster is 30 ± 20 ℃, and therefore, the bag temperature is 1535 ± 20 ℃ in the control continuous caster.This temperature is that the electrically heated by front LF stove realizes.
Preferably, calcium carbide contains CaC described in the aforesaid method
2More than 70%.With handled easily with avoid adding too much impurity.
The invention will be further described below by embodiment, but therefore do not limit the present invention among the scope of description of embodiment.
Embodiment one
Adopt the technology of the present invention to produce the 23MnB steel at 120 tons of nominal capacities, the actual tap bof process in 120～140 tons of scopes, production technique is that 120 tons of converters are just made steel water → 120 ton LF stove heating refined molten steel → 120 a ton RH vacuum cycle and processed molten steel → 6 machines, 6 stream billet casters and be cast into 280mm * 380mm strand.
At first in converter, add 130 tons of molten iron and 10 tons of steel scraps, utilize Converter Oxigen Blowing to take off the function of C, molten iron and steel scrap just are smelt molten steel, tap when the C of just refining of molten steel composition to 0.05%, 0.020% P, 0.015% S, 0.01% Si and 0.05% Mn in the ladle, this moment, actual tap was 133 tons, and about 5% raw material is by scaling loss in the converter steelmaking process.In molten steel, add calcium carbide 530kg in the tapping process, calcium carbide contains CaC275%, and add simultaneously that FeSi, FeMn alloy and hard coal carry out Si, Mn and C is element alloyed, Si content is 74% in the FeSi alloy that wherein adds, Mn content is 82% in the FeMn alloy, fixation of C is 92% in the hard coal, and Si content is 0.16% in the control molten steel, Mn content is 1.10%, C content is 0.20%.Gone out in the molten steel in the backward ladle of steel feeding Al line, control Als is 0.015%, and having fed behind the Al line with apparatus for determination of oxygen mensuration molten steel oxygen activity α [O] is 0.0015%.
Molten steel begins electrically heated after arriving the LF stove, and then stopped heating when liquid steel temperature is heated to 1590 ℃ moves on to ladle the RH vacuum treatment installation and carry out vacuum-treat.
Molten steel begins to carry out vacuum-treat after arriving the RH vacuum treatment installation, pressure in vacuum tank reached 300Pa and added the 17kg aluminum shot after 5 minute, add that the recovery rate of aluminium is about 80% behind the aluminum shot this moment, add aluminum shot after 2 minutes, add 90kg FeTi40 ferrotianium (namely contain Ti be 40% iron alloy) and 10kgFeB23 ferro-boron (namely contain B be 23% iron alloy), added behind ferrotianium and the ferro-boron under the ultimate pressure condition recycling processing 3 minutes, the Als of sampling and measuring molten steel is 0.025%, Ti is 0.02%, B is 0.0014%, the recovery rate of B is 80%, then send molten steel to cast to continuous caster.
Become 280mm * 380mm strand in the 6 stream billet caster top castings of 6 machines, tundish temperature is 1520 ℃ during continuous casting, bag sampling analysis molten steel chemical composition is 0.20% C, 0.15% Si, 1.10% Mn, 0.020% P, 0.014% S, 0.12% Cr, 0.06% Ni, 0.10% Cu, 0.0012% B in continuous caster, and the Als of 0.02% Ti and 0.020% (Als scaling loss 0.005% in the casting cycle), all the other are Fe and inevitable other impurity.
Embodiment two
Adopt the technology of the present invention to produce the 23MnB steel at 120 tons of nominal capacities, the actual tap bof process in 120～140 tons of scopes, production technique is that 120 tons of converters are just made steel water → 120 ton LF stove refined molten steel → 120 tons of RH vacuum cycle and processed molten steel → 6 machines, 6 stream billet casters and be cast into 360mm * 450mm strand.
At first in converter, add 120 tons of molten iron and 20 tons of steel scraps, utilize Converter Oxigen Blowing to take off the function of C, molten iron and steel scrap just are smelt molten steel, tap when the C of just refining of molten steel composition to 0.15%, 0.015% P, 0.010% S, 0.01% Si and 0.05% Mn in the ladle, this moment, actual tap was 133 tons, and about 5% raw material is by scaling loss in the converter steelmaking process.In molten steel, add calcium carbide 400kg in the tapping process, calcium carbide contains CaC275%, and add simultaneously that FeSi, FeMn alloy and hard coal carry out Si, Mn and C is element alloyed, Si content is 74% in the FeSi alloy that wherein adds, Mn content is 82% in the FeMn alloy, fixation of C is 92% in the hard coal, and Si content is 0.35% in the control molten steel, Mn content is 0.80%, C content is 0.27%.Gone out in the molten steel in the backward ladle of steel feeding Al line, control Als is 0.025%, and having fed behind the Al line with apparatus for determination of oxygen mensuration molten steel oxygen activity α [O] is 0.0012%.
Molten steel begins electrically heated after arriving the LF stove, and then stopped heating when liquid steel temperature is heated to 1610 ℃ moves on to ladle the RH vacuum treatment installation and carry out vacuum-treat.
Molten steel begins to carry out vacuum-treat after arriving the RH vacuum treatment installation, pressure in vacuum tank reached 300Pa and added the 17kg aluminum shot after 5 minute, add that the recovery rate of aluminium is about 80% behind the aluminum shot this moment, add aluminum shot after 2 minutes, add 130kg FeTi40 ferrotianium (namely contain Ti be 40% iron alloy) and 15kgFeB23 ferro-boron (namely contain B be 23% iron alloy), added behind ferrotianium and the ferro-boron under the ultimate pressure condition recycling processing 5 minutes, the Als of sampling and measuring molten steel is 0.035%, Ti is 0.031%, B is 0.0021%, the recovery rate of B is 75%, then send molten steel to cast to continuous caster.
Become 360mm * 450mm strand in the 6 stream billet caster top castings of 6 machines at last, tundish temperature is 1555 ℃ during continuous casting, bag sampling analysis molten steel chemical composition is 0.27% C, 0.35% Si, 0.81% Mn, 0.015% P, 0.009% S, 0.12% Cr, 0.06% Ni, 0.16% Cu, 0.0021% B in continuous caster, and the Als of 0.031% Ti and 0.027% (Als scaling loss 0.008% in the casting cycle), all the other are Fe and inevitable other impurity.
Embodiment three
Adopt the technology of the present invention to produce the 23MnB steel at 120 tons of nominal capacities, the actual tap bof process in 120～140 tons of scopes, production technique is that 120 tons of converters are just made steel water → 120 ton LF stove refined molten steel → 120 tons of RH vacuum cycle and processed molten steel → 6 machines, 6 stream billet casters and be cast into 280mm * 380mm strand.
At first in converter, add 140 tons of molten iron, utilize Converter Oxigen Blowing to take off the function of C, molten iron just is smelt molten steel, tap when the C of just refining of molten steel composition to 0.10%, 0.025% P, 0.009% S, 0.01% Si and 0.05% Mn in the ladle, this moment, actual tap was 133 tons, and about 5% raw material is by scaling loss in the converter steelmaking process.In molten steel, add calcium carbide 530kg in the tapping process, calcium carbide contains CaC275%, and add simultaneously that FeSi, FeMn alloy and hard coal carry out Si, Mn and C is element alloyed, wherein Si content is 74% in the FeSi alloy, Mn content is 82% in the FeMn alloy, fixation of C is 92% in the hard coal, Si content is 0.25% in the control molten steel, Mn content is 1.01%, C content is 0.23%, gone out feeding Al line in the molten steel in the backward ladle of steel, control Als is 0.020%, and having fed behind the Al line with apparatus for determination of oxygen mensuration molten steel oxygen activity α [O] is 0.0013%.
Molten steel begins electrically heated after arriving the LF stove, and then stopped heating when liquid steel temperature is heated to 1600 ℃ moves on to ladle the RH vacuum treatment installation and carry out vacuum-treat.
Molten steel begins to carry out vacuum-treat after arriving the RH vacuum treatment installation, pressure in vacuum tank reaches 300Pa and through adding 33kg aluminum shot (add this moment the recovery rate of aluminium is about 80% behind the aluminum shot) after 5 minutes, add aluminum shot after 2 minutes, add 250kg FeTi40 ferrotianium (namely contain Ti be 40% iron alloy) and 20kgFeB23 ferro-boron (namely contain B be 23% iron alloy), added behind ferrotianium and the ferro-boron under the ultimate pressure condition recycling processing 8 minutes, the Als of sampling and measuring molten steel is 0.04%, Ti is 0.06%, B is 0.0024%, the recovery rate of B is 70%, then send molten steel to cast to continuous caster.
Become 280mm * 380mm strand in the 6 stream billet caster top castings of 6 machines at last, tundish temperature is 1530 ℃ during continuous casting, bag sampling analysis molten steel chemical composition is 0.23% C, 0.25% Si, 1.09% Mn, 0.025% P, 0.009% S, 0.06% Cr, 0.06% Ni, 0.05% Cu, 0.0022% B in continuous caster, and the Als of 0.06% Ti and 0.033% (Als scaling loss 0.007% in the casting cycle), all the other are Fe and inevitable other impurity.
Embodiment four
Adopt the technology of the present invention to produce the 23MnB steel at 120 tons of nominal capacities, the actual tap bof process in 120～140 tons of scopes, production technique is that 120 tons of converters are just made steel water → 120 ton LF stove refined molten steel → 120 tons of RH vacuum cycle and processed molten steel → 6 machines, 6 stream billet casters and be cast into 360mm * 450mm strand.
At first in converter, add 120 tons of molten iron and 20 tons of steel scraps, utilize Converter Oxigen Blowing to take off the function of C, molten iron and steel scrap just are smelt molten steel, tap when the C of just refining of molten steel composition to 0.15%, 0.015% P, 0.010% S, 0.01% Si and 0.05% Mn in the ladle, this moment, actual tap was 133 tons, and about 5% raw material is by scaling loss in the converter steelmaking process.In molten steel, add calcium carbide 400kg in the tapping process, calcium carbide contains CaC275%, and add simultaneously that FeSi, FeMn alloy and hard coal carry out Si, Mn and C is element alloyed, Si content is 74% in the FeSi alloy that wherein adds, Mn content is 82% in the FeMn alloy, fixation of C is 92% in the hard coal, and Si content is 0.35% in the control molten steel, Mn content is 0.80%, C content is 0.27%.Gone out in the molten steel in the backward ladle of steel feeding Al line, control Als is 0.025%, and having fed behind the Al line with apparatus for determination of oxygen mensuration molten steel oxygen activity α [O] is 0.0012%.
Molten steel begins electrically heated after arriving the LF stove, and then stopped heating when liquid steel temperature is heated to 1610 ℃ moves on to ladle the RH vacuum treatment installation and carry out vacuum-treat.
Molten steel begins to carry out vacuum-treat after arriving the RH vacuum treatment installation, pressure in vacuum tank reaches 300Pa and through adding 50kg aluminum shot (add this moment the recovery rate of aluminium is about 80% behind the aluminum shot) after 5 minutes, add aluminum shot after 2 minutes, add 130kg FeTi40 ferrotianium (namely contain Ti be 40% iron alloy) and 15kgFeB23 ferro-boron (namely contain B be 23% iron alloy), added behind ferrotianium and the ferro-boron under the ultimate pressure condition recycling processing 5 minutes, the Als of sampling and measuring molten steel is 0.055%, Ti is 0.031%, B is 0.0021%, the recovery rate of B is 75%, then send molten steel to cast to continuous caster.
Become 360mm * 450mm strand in the 6 stream billet caster top castings of 6 machines at last, tundish temperature is 1555 ℃ during continuous casting, bag sampling analysis molten steel chemical composition is 0.27% C, 0.35% Si, 0.81% Mn, 0.015% P, 0.009% S, 0.12% Cr, 0.06% Ni, 0.16% Cu, 0.0021% B in continuous caster, and the Als of 0.031% Ti and 0.05% (Als scaling loss 0.005% in the casting cycle), all the other are Fe and inevitable other impurity.
The comparative example
Adopt the technology of the present invention to produce the 23MnB steel at 120 tons of nominal capacities, the actual tap bof process in 120～140 tons of scopes, production technique is that 120 tons of converters are just made steel water → 120 ton LF stove refined molten steel → 120 tons of RH vacuum cycle and processed molten steel → 6 machines, 6 stream billet casters and be cast into 280mm * 380mm strand.
At first in converter, add 140 tons of molten iron, utilize Converter Oxigen Blowing to take off the function of C, molten iron just is smelt molten steel, tap when the C of just refining of molten steel composition to 0.10%, 0.025% P, 0.009% S, 0.01% Si and 0.05% Mn in the ladle, this moment actual tap be in 133 tons, converter steelmaking process about 5% raw material by scaling loss.Add calcium carbide 530kg calcium carbide in the tapping process in the molten steel and contain CaC
275%, and add simultaneously that FeSi, FeMn alloy and hard coal carry out Si, Mn and C is element alloyed, wherein Si content is 74% in the FeSi alloy, Mn content is 82% in the FeMn alloy, fixation of C is 92% in the hard coal, and Si content is 0.25% in the control molten steel, Mn content is 1.01%, C content is 0.23%, has gone out feeding Al line in the molten steel in the backward ladle of steel, control Als is 0.025%, has fed behind the Al line with apparatus for determination of oxygen mensuration molten steel oxygen activity α
[O]Be 0.0012%.
Molten steel begins electrically heated after arriving the LF stove, and then stopped heating when liquid steel temperature is heated to 1600 ℃ moves on to ladle the RH vacuum treatment installation and carry out vacuum-treat.
Molten steel begins to carry out vacuum-treat after arriving the RH vacuum treatment installation, pressure in vacuum tank reaches 300Pa and through adding 67kg aluminum shot (add this moment the recovery rate of aluminium is about 80% behind the aluminum shot) after 5 minutes, add aluminum shot after 2 minutes, add 250kg FeTi40 ferrotianium (namely contain Ti be 40% iron alloy) and 20kgFeB23 ferro-boron (namely contain B be 23% iron alloy), added behind ferrotianium and the ferro-boron under the ultimate pressure condition recycling processing 8 minutes, the Als of sampling and measuring molten steel is 0.065%, Ti is 0.06%, B is 0.0024%, the recovery rate of B is 70%, then send molten steel to cast to continuous caster.
Become 280mm * 380mm strand in the 6 stream billet caster top castings of 6 machines at last, tundish temperature is 1530 ℃ during continuous casting, bag sampling analysis molten steel chemical composition is 0.23% C, 0.25% Si, 1.09% Mn, 0.025% P, 0.009% S, 0.06% Cr, 0.06% Ni, 0.05% Cu, 0.0022% B in continuous caster, and the Als of 0.06% Ti and 0.055% (Als scaling loss 0.01% in the casting cycle), all the other are Fe and inevitable other impurity.Continuous caster is found the aluminium secondary oxidation is arranged and the continuous caster mouth of a river that the causes phenomenon that diminishes in casting cycle, continuous caster the 3rd and the 5th stream casting speed can not meet the requirements of 7.0m/min, can only cast with the casting speed of 4.5～5.0m/min (continuous caster the 3rd and the 5th stream casting speed can only carry out the impact casting to set 70% of casting speed).
Above-described embodiment explanation adopts the technology of the present invention to produce the 23MnB steel, whole process control effectively to molten steel oxygen activity and acid-soluble aluminum content, tapping process does not adopt aluminium to carry out pre-deoxidation, and the employing calcium carbide, final Als is controlled in 0.02～0.05% scope, more preferably be controlled in 0.025～0.035% scope, the recovery rate of boron is more than 70% behind the adding ferro-boron, be in higher level, both guaranteed the effect that boron improves hardening capacity, in casting bloom process, the phenomenon of having avoided the continuous caster mouth of a river to diminish is cast smoothly again.
Claims (9)
1. the method for producing 23 MnB steel by adopting vacuum process is characterized in that comprising the steps:
A, in converter, add molten iron smelting;
B, molten steel are tapped to ladle, in molten steel, add calcium carbide during tapping, the calcium carbide consumption is foundation according to endpoint carbon content of converter, when converter terminal carbon weight percent drops into by molten steel 3.5～4.5kg per ton when following 0.10%, when converter terminal carbon weight percent drops into by molten steel 2.5～3.5kg per ton greater than 0.10%, less than 0.15% the time, when converter terminal carbon weight percent 0.15% when above by molten steel 1.5～2.5kg input per ton; Add again aluminium, make the weight percent content of sour molten aluminium in the molten steel 0.014～0.019%;
C, ladle move into the refining of LF stove;
After d, the refining ladle is moved into the RH vacuum treatment installation and carry out the vacuum cycle processing, in molten steel, add aluminium in the processing, make in the molten steel sour molten aluminium weight percent content 0.025～0.055%, add again titanium and make in the molten steel titanium weight percent content 0.02～0.06%, add boron and make in the molten steel boron weight percent content 0.0005～0.003%;
E, vacuum cycle are carried out continuous casting after processing.
2. the method for producing 23 MnB steel by adopting vacuum process according to claim 1 is characterized in that: in the steps d, add aluminium in molten steel, make in the molten steel sour molten aluminium weight percent content 0.035～0.04%.
3. the method for producing 23 MnB steel by adopting vacuum process according to claim 1 is characterized in that: also add steel scrap when adding molten iron in the converter among the step a, the weight of steel scrap can not surpass 15% of weight of molten iron.
4. the method for producing 23 MnB steel by adopting vacuum process according to claim 3 is characterized in that: when just refining of molten steel composition to C by weight percentage is 0.05%～0.15%, in the ladle of molten steel being tapped when P≤0.030% and S≤0.015%.
5. the method for producing 23 MnB steel by adopting vacuum process according to claim 1 is characterized in that: also add when adding calcium carbide among the step b ferrosilicon make in the molten steel silicon weight percent content 0.15～0.35%, add ferromanganese make in the molten steel manganese weight percent content 0.80%～1.10%, add carburelant and make the carbon weight percent content 0.20～0.27%.
6. the method for producing 23 MnB steel by adopting vacuum process according to claim 1, it is characterized in that: among the step c, stopped heating when molten steel is heated to 1590～1610 ℃ moves into the RH vacuum treatment installation with ladle.
7. the method for producing 23 MnB steel by adopting vacuum process according to claim 1 is characterized in that: pressure≤300Pa when the steps d vacuum cycle is processed, 10～15 minutes treatment times.
8. the method for producing 23 MnB steel by adopting vacuum process according to claim 1 is characterized in that: during step e continuous casting in the continuous caster bag temperature be 1535 ± 20 ℃.
9. the method for producing 23 MnB steel by adopting vacuum process according to claim 1, it is characterized in that: described calcium carbide contains CaC
2More than 70%.
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| TWI515301B (en) * | 2012-03-08 | 2016-01-01 | 杰富意鋼鐵股份有限公司 | Method for manufacturing ultra low carbon steel by using vacuum-degassing system |
| CN105274281A (en) * | 2014-06-23 | 2016-01-27 | 鞍钢股份有限公司 | Method for accurately controlling boron content in steel |
| CN107012287B (en) * | 2017-04-18 | 2019-04-26 | 攀钢集团攀枝花钢铁研究院有限公司 | Smelting process for heat stamping and shaping steel |
| CN108588541B (en) * | 2018-03-09 | 2020-05-26 | 江苏省沙钢钢铁研究院有限公司 | Low-nitrogen boron-containing steel smelting method for improving boron element yield |
| EP3940088B1 (en) * | 2019-03-13 | 2023-11-22 | JFE Steel Corporation | Method for producing ti-containing ultralow-carbon steel |
| CN111118387B (en) * | 2019-12-13 | 2021-07-23 | 河钢乐亭钢铁有限公司 | Method for improving surface quality of boron-containing steel continuous casting slab |
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| CN101660101A (en) * | 2009-09-28 | 2010-03-03 | 莱芜钢铁股份有限公司 | Steel for low-carbon wear-resistant engineering machinery creeper tread and manufacturing method thereof |
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| CN101045948A (en) * | 2007-04-29 | 2007-10-03 | 攀钢集团攀枝花钢铁研究院 | Method for producing boron steel by smelting in converter |
| CN101503746A (en) * | 2009-03-19 | 2009-08-12 | 新余钢铁股份有限公司 | Method for producing boron steel by converter |
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