CN104087705B - Control the method for high nitrogen steel nitrogen content - Google Patents
Control the method for high nitrogen steel nitrogen content Download PDFInfo
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- CN104087705B CN104087705B CN201410353852.9A CN201410353852A CN104087705B CN 104087705 B CN104087705 B CN 104087705B CN 201410353852 A CN201410353852 A CN 201410353852A CN 104087705 B CN104087705 B CN 104087705B
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Abstract
The invention discloses a kind of method controlling high nitrogen steel nitrogen content, described method comprises: in converter smelting step, adopts omnidistance bottom blowing nitrogen pattern to carry out nitrogen pick-up, and wherein, the gas supply flow smelted before mid-term to tapping is greater than the gas supply flow after smelting initial stage and tapping; In LF refinement step, carry out nitrogen pick-up by twice feeding nitrogen-containing alloy line, wherein, perform the first line feeding operation when LF enters the station with the nitrogen-containing alloy line feeding the first amount, perform the second line feeding operation when LF sets off with the nitrogen-containing alloy line feeding the second amount.The control accuracy of high nitrogen steel nitrogen content can be improved according to method of the present invention, avoid causing subsurface bubble because nitrogen content in finished steel is too high and causing Pull crack defect, improve the quality of products, make the Control of Nitrogen Content of finished product height nitrogen steel at 100ppm ~ 150ppm.
Description
Technical field
The present invention relates to field of iron and steel smelting, particularly relate to a kind of method controlling high nitrogen steel nitrogen content.
Background technology
Along with high speed and the heavy loading of China railways, to the material manufacturing train crossbeam---the requirement of the quality index such as the intensity of high strength height nitrogen steel, atmospheric corrosion resistance and low temperature impact properties, also more and more higher.And the Control of Nitrogen Content in steel, determine the steel product quality such as yield strength and low temperature impact properties of steel.If Control of Nitrogen Content is too low, then the yield strength of steel does not reach requirement, if Control of Nitrogen Content is too high, then [N] in casting process in molten steel, in free state, easily produces subsurface bubble, thus causes steel surface lobe, transverse fissure and subcrack.
When smelting high-nitrogen steel, way general is at present nitrogen flushing or add nitrogen-containing alloy carry out nitrogen pick-up in refinery practice before converter terminal.But often nitrogen content is on the low side when converter tapping for this technique, make the nitrogen pick-up pressure of the subsequent techniques such as refining very large, nitrogen content not easily accurately controls, and component content fluctuation range is very large, causes the nitrogen content of product steel to exceed standard.
Summary of the invention
The object of the invention is to the nitrogen pick-up technique improving converter smelting and LF refining, strengthen the nitrogen pick-up effect of converter smelting and improve the nitrogen pick-up control accuracy of LF refining, making the Control of Nitrogen Content of Finished Steel in metastable close limit.
The invention provides a kind of method controlling high nitrogen steel nitrogen content, described method comprises converter smelting step and LF refinement step, converter smelting adopts omnidistance bottom blowing nitrogen pattern to carry out nitrogen pick-up, and wherein, the gas supply flow smelted before mid-term to tapping is greater than the gas supply flow after smelting initial stage and tapping; LF refining carrys out nitrogen pick-up by twice feeding nitrogen-containing alloy line, wherein, performing the first line feeding operation with the nitrogen-containing alloy line feeding the first amount when entering the station, performing the second line feeding operation with the nitrogen-containing alloy line feeding the second amount when setting off.
According to exemplary embodiment of the present invention, in converter smelting step, the gas supply flow smelted in initial stage and tapping process can be 120m
3/ h ~ 300m
3/ h, the gas supply flow smelted before mid-term to tapping can be 300m
3/ h ~ 750m
3/ h.
According to exemplary embodiment of the present invention, smelting mid-term, the gas supply flow after catch carbon can be reduced to 120m
3/ h ~ 300m
3/ h, after smelting for some time, then with 300m
3/ h ~ 750m
3the gas supply flow of/h is re-blow to tapping.
According to exemplary embodiment of the present invention, the gas supply flow after terminating with tapping before starting blowing is 50m
3/ h ~ 80m
3/ h.
According to exemplary embodiment of the present invention, nitrogen-containing alloy line can comprise the nitrogen of 4.5wt% ~ 7.5wt%.
According to exemplary embodiment of the present invention, in LF refinement step, the total amount of the nitrogen-containing alloy line that twice line feeding operation feeds altogether can be 2m/ ton steel ~ 4.5m/ ton steel.
According to exemplary embodiment of the present invention, in the first line feeding operation, the nitrogen-containing alloy line of the first amount of feeding can be 2m/ ton steel ~ 3.5m/ ton steel, and in the second line feeding operation, the nitrogen-containing alloy line of the second amount of feeding can be 0m/ ton steel ~ 1m/ ton steel.
According to exemplary embodiment of the present invention, in converter smelting step, the nitrogen content that tapping terminates rear molten steel can control at 45ppm ~ 50ppm.
According to exemplary embodiment of the present invention, in LF refinement step, after executing the first line feeding operation, the nitrogen content of molten steel can control at 90ppm ~ 100ppm.
According to exemplary embodiment of the present invention, in LF refinement step, after executing the second line feeding operation, the nitrogen content of molten steel can control at 100ppm ~ 120ppm.
The present invention can obtain at least one in following beneficial effect:
By twice line feeding operation of the whole process of converter smelting blowing model and LF refining stage by stage, improve the nitrogen pick-up level of converter smelting step, alleviate the nitrogen pick-up pressure of follow-up LF refinement step, improve control accuracy and the final product quality of nitrogen content.
Accompanying drawing explanation
According to below in conjunction with the accompanying drawing description of this invention, these and/or other aspect of the present invention will become obviously and be easier to understand, in the accompanying drawings:
Fig. 1 is the omnidistance bottom blowing nitrogen blowing model figure of the converter smelting step according to exemplary embodiment of the present invention;
Nitrogen content of molten steel distribution plan when Fig. 2 is the LF refinement step departures according to exemplary embodiment of the present invention;
Fig. 3 is the nitrogen content distribution plan utilizing the Finished Steel obtained according to the method for the control of exemplary embodiment of the present invention high nitrogen steel nitrogen content.
Embodiment
Below in conjunction with embodiment, the invention will be further elaborated, but following embodiment only plays exemplary illustration, can not be used for limiting the present invention.Unless specifically stated otherwise, involved per-cent is all weight percentage, and hereinafter NM other aspects related to the present invention can be realized by known technology.
Nitrogen can be dissolved in iron.In α-Fe, the solubleness of nitrogen element at 591 DEG C is 0.1%, and solubleness at room temperature only has 0.001%.Therefore, nitrogen can be solid-solution in steel.When nitrogen element is present in steel with the form of nitride, austenite can be stoped to grow up, the crystal size of refinement steel, thus the mechanical property improving steel, particularly yield strength and low temperature impact properties.But excessive nitrogen element is present in steel with the form of gas, steel are easily made to produce subsurface bubble and loosen.Therefore, during the smelting of the high nitrogen steel using nitrogen as alloy element, be how the key factor affecting quality product by Control of Nitrogen Content in the scope expected.
Exemplary embodiment of the present invention, mainly through improving the nitrogen pick-up technique of converter smelting and LF refining two steps, realizes the accurate control to high nitrogen steel nitrogen content.Method according to the control of exemplary embodiment of the present invention high nitrogen steel nitrogen content comprises: in converter smelting step, omnidistance bottom blowing nitrogen pattern is adopted to carry out nitrogen pick-up, wherein, take different air supply intensities respectively in the different steps of converter smelting, the gas supply flow smelted before mid-term to tapping is greater than the gas supply flow after smelting initial stage and tapping; In LF refinement step, carry out nitrogen pick-up by twice feeding nitrogen-containing alloy line, wherein, performing the first line feeding operation when entering the station with the nitrogen-containing alloy line feeding the first amount, performing the second line feeding operation when setting off with the nitrogen-containing alloy line feeding the second amount.
At present, converter smelting step generally carrys out nitrogen pick-up by being blown into nitrogen at the smelting initial stage, stops for nitrogen immediately after smelting for some time, then is blown into argon shielding gas until tapping terminates.Because in smelting initial stage stove, oxygen supply is sufficient, reaction between carbon and oxygen is violent, the CO produced is made to have stronger denitrification ability, therefore the nitrogen be blown into has a big chunk to lose with the wallop in molten bath, do not have good nitrogen pick-up effect, cause the nitrogen content of molten steel after tapping lower and fluctuate comparatively large, adding the processing pressure of follow-up refinement step.
Fig. 1 is the omnidistance bottom blowing nitrogen blowing model figure of the converter smelting step according to exemplary embodiment of the present invention.As shown in Figure 1, converter smelting adopts omnidistance bottom blowing nitrogen pattern, wherein, takes different air supply intensities respectively in the different steps of converter smelting.According to the mass transport mechanism of chemical reaction, the limiting element of the dissolution process of nitrogen in molten steel is diffusion, and at the smelting initial stage, impact by the Oxygen Flow in stove, the speed that nitrogen spreads in molten steel can slow down, and the initial stage of therefore smelting should not adopt excessive flow.Nitrogen flow according to the smelting initial stage of exemplary embodiment of the present invention can control at 120m
3/ h ~ 300m
3/ h, in the present embodiment, the nitrogen flow smelting the initial stage controls at 200m
3/ h.
When smelting enters mid-term, along with the carrying out of blowing, in stove, decarburizing reaction is tending towards perfect, and the ferric oxide in slag reduces, and the velocity of nitrogen absorption in molten bath significantly increases, and now suitably should increase gas supply flow and make molten steel nitrogen pick-up.Therefore, nitrogen flow, when converter smelting enters mid-term, is increased to 300m by exemplary embodiment of the present invention
3/ h ~ 750m
3/ h.In the present embodiment, the nitrogen flow in converter smelting mid-term controls at 600m
3/ h, then keeps this flow to blow to starting tapping always.
In addition, according to exemplary embodiment of the present invention, also the stage of re-blowing is comprised before tapping, this is because no longer oxygen supply in stove after catch carbon, reaction between carbon and oxygen no longer produces CO, thus the denitrification ability of molten steel is significantly weakened, if now to re-blow nitrogen with large discharge, then molten steel can be made during this farthest to inhale nitrogen.Therefore, stage nitrogen flow of re-blowing of the present invention reaches 300m
3/ h ~ 750m
3/ h is identical with the nitrogen flow smelting mid-term.As shown in Figure 1, in the present embodiment, the nitrogen flow in stage of re-blowing can control at 600m
3/ h.But the present invention is not limited thereto, the nitrogen flow in stage of re-blowing can be not identical with the nitrogen flow smelting mid-term yet.
In addition, according to exemplary embodiment of the present invention, after catch carbon, re-blow before, nitrogen flow can reduce by a small margin, such as, is down to 120m
3/ h ~ 300m
3/ h, and the 300m again returning to the stage of re-blowing after keeping for some time again
3/ h ~ 750m
3/ h.As shown in Figure 1, in the present embodiment, nitrogen flow is decreased to 240m after catch carbon
3/ h, after keeping for some time, returns to 600m again when entering and re-blowing the stage
3/ h.The effect of this measure is: make molten steel after oxygen feeding stop, and inner heat transfer and the carrying out of mass transfer can have buffering course, thus guarantee the temperature of molten steel and being more evenly distributed of composition, and stirring kinetic energy is utilized more fully.
When the main component of molten steel meets C≤0.15%, P≤0.015%, S≤0.015%, namely reaching converter smelting endpoint can tap.Tapping temperature controls at 1680 DEG C ~ 1710 DEG C, and average tapping time controling is at 5.3min.Deoxidation alloying is carried out by adding aluminium ferromanganese and feeding aluminum steel, the whole process of tapping not blowing argon gas and continue to keep nitrogen flushing during tapping.When tapping, in order to avoid, nitrogen flow is too high causes molten steel disturbance to bring disadvantageous effect to tapping process, needs nitrogen flow to be decreased to 120m
3/ h ~ 300m
3/ h, then keeps nitrogen flushing until tap complete.In the present embodiment, from tapping to tapping complete, nitrogen flow is controlled at 240m
3/ h.
In addition, as shown in fig. 1, before starting blowing and tapping complete after, also need nitrogen flushing to eliminate foreign material in pipeline and equipment to prevent line clogging, ensure that the nitrogen flow of whole converting process is supplied unblocked.The nitrogen flow be blown in this two stages can be less, as long as can reach the object of dredging pipeline.Gas supply flow after the present invention terminates with tapping before starting blowing, controls at 50m
3/ h ~ 80m
3/ h.In the present embodiment, 50m is preferably
3/ h.
After tapping terminates, carry out the process of steel-making chain-wales, analyze nitrogen content.According to exemplary embodiment of the present invention, tapping terminates the Control of Nitrogen Content of rear molten steel at 45ppm ~ 50ppm, compared with the nitrogen content level of average about the 35ppm of prior art, obviously increases, this will alleviate the nitrogen pick-up pressure of follow-up LF refinement step effectively, reduces production cost.
Because the span of control of high nitrogen steel to C, Mn and Cr has stricter requirement, therefore LF refining must ensure constituent adjustment ability.In LF refinement step, in order to accurately control nitrogen content, the present invention adopts and carrys out nitrogen pick-up by the method for twice feeding nitrogen-containing alloy line.
When LF enters the station, perform the first line feeding operation, calculate the amount (that is, the nitrogen-containing alloy line of the first amount) of the nitrogen-containing alloy line of feeding according to the nitrogen content analyzed during chain-wales process.Next, after performing slagging operation 5min ~ 8min, sampling analysis nitrogen content, is designated as the nitrogen content recorded the nitrogen content that enters the station, according to exemplary embodiment of the present invention, after executing the first line feeding operation, the nitrogen content (enter the station nitrogen content) of molten steel controls at 90ppm ~ 100ppm.
Then, by ladle heating with the controlling and adjustment carrying out temperature or other compositions, then the amount of the nitrogen-containing alloy line of feeding is calculated (namely according to the nitrogen content that enters the station, the nitrogen-containing alloy line of the second amount), then the second line feeding operation is performed, following execution soft blow operation, sampling analysis nitrogen content, is designated as departures nitrogen content by the nitrogen content recorded.According to exemplary embodiment of the present invention, after executing the second line feeding operation, the nitrogen content (departures nitrogen content) of molten steel controls at 100ppm ~ 120ppm.It should be noted that after executing the first line feeding operation, determine whether that execution second line feeding operates according to the detected result of the nitrogen content that enters the station.In other words, after the nitrogen-containing alloy line of feeding first amount, if the nitrogen content of detected result display molten steel reaches the standard of departures nitrogen content, then the nitrogen-containing alloy line feeding the second amount can be 0.
Preferably, this nitrogen-containing alloy line can be vanadium titanium wire (VT line).The line feeding method according to exemplary embodiment of the present invention is described in detail below for vanadium titanium wire.
Table 1 shows the composition of the VT line according to exemplary embodiment of the present invention.
Show 1VT line main component and contain scale (wt%)
| C | V | N | Ti |
| 6.0 | 61.0～66.0 | 4.5～7.5 | 4.0～8.0 |
As shown in Table 1, the main component of the VT line of the present embodiment is vanadium, titanium and nitrogen, and also containing a small amount of carbon, surplus is iron and inevitable impurity.Wherein, the effect of vanadium is adjusting component, and the effect of titanium is crystal grain thinning, and the effect of nitrogen improves intensity, and the effect of carbon is adjusting component.After adopting the line feeding method according to exemplary embodiment of the present invention, in this VT line, the recovery rate of each element is also significantly increased according to than before improvement, wherein, the recovery rate of nitrogen brings up to 30% ~ 50% by 20% ~ 30%, and the recovery rate of vanadium brings up to 92% ~ 95% by 88% ~ 90%.
In addition, according to exemplary embodiment of the present invention, in order to improve the level of control of nitrogen content further and guarantee that ladle uniform composition distributes, after executing the second line feeding operation, carry out soft blow argon to molten steel, argon flow amount can be 10m
3/ h ~ 50m
3/ h, soft argon blowing time can be not less than 6min.
Below, the present invention is further described by concrete example.
Example 1:
Converter smelting step: control nitrogen flow 50m after terminating with tapping before starting blowing
3/ h.The nitrogen flow 200m at smelting initial stage
3/ h, blowing 8min, increases to 600m by nitrogen flow
3/ h, catch carbon after blowing 12min, is reduced to 240m by nitrogen flow
3/ h, nitrogen of re-blowing after catch carbon terminates, nitrogen flow increases to 600m again
3/ h, blows to molten steel and meets tapping condition.Continue nitrogen flushing in tapping process, and keep nitrogen flow to be 240m
3/ h is until tap complete, and the nitrogen content measuring molten steel is 50ppm.
LF refinement step: the VT line 3m/ ton steel of feeding the first amount in the first line feeding operation, the nitrogen content that enters the station measuring molten steel is 105ppm, then slag, heating, modifying ingredients is changed, then the second line feeding operation is performed with the VT line 0.5m/ ton steel feeding the second amount, take out station sample, then to molten steel soft blow argon, argon flow amount is 20m
3/ h, soft argon blowing time 6min, the departures nitrogen content measuring molten steel is 123ppm.
The nitrogen content of final acquisition Finished Steel is 128ppm.
Example 2:
Converter smelting step: the nitrogen flow 200m smelting the initial stage
3/ h, blowing 10min, increases to 600m by nitrogen flow
3/ h, catch carbon after blowing 12min, is reduced to 240m by nitrogen flow
3/ h, nitrogen of re-blowing after catch carbon terminates, nitrogen flow increases to 600m again
3/ h, blows to molten steel and meets tapping condition.Continue nitrogen flushing in tapping process, and keep nitrogen flow to be 240m
3/ h is until tap complete, and the nitrogen content measuring molten steel is 47ppm.
LF refinement step: the VT line 3m/ ton steel of feeding the first amount in the first line feeding operation, the nitrogen content that enters the station measuring molten steel is 100ppm, then slag, heating, modifying ingredients is changed, then the second line feeding operation is performed with the VT line 0.5m/ ton steel feeding the second amount, take out station sample, then to molten steel soft blow argon, argon flow amount is 20m
3/ h, soft argon blowing time 6min, the departures nitrogen content measuring molten steel is 120ppm.
The nitrogen content of final acquisition Finished Steel is 126ppm.
Nitrogen content of molten steel distribution plan when Fig. 2 is the LF refinement step departures according to exemplary embodiment of the present invention, Fig. 3 is the nitrogen content distribution plan utilizing the Finished Steel obtained according to the method for the control of exemplary embodiment of the present invention high nitrogen steel nitrogen content.As shown in Figure 2, the nitrogen content of molten steel only fluctuation within a narrow range between 100ppm ~ 130ppm during the departures of LF refinement step, technology controlling and process level improves a lot, for stable finished product nitrogen content lays good basis.As shown in Figure 3, the Control of Nitrogen Content of the final Finished Steel obtained is between 100ppm ~ 150ppm, and steady quality, qualification rate is very high.
But; the present invention is not limited to above-described embodiment; any those skilled in the art without departing from the spirit and scope of the present invention, can make possible variation and amendment, and therefore protection scope of the present invention should be as the criterion with the scope defined in claims.
Claims (8)
1. control a method for high nitrogen steel nitrogen content, described method comprises:
In converter smelting step, adopt the pattern of omnidistance bottom blowing nitrogen to carry out nitrogen pick-up, wherein, the gas supply flow smelted before mid-term to tapping is greater than the gas supply flow after smelting initial stage and tapping;
In LF refinement step, carry out nitrogen pick-up by twice feeding nitrogen-containing alloy line, wherein, perform the first line feeding operation when LF enters the station with the nitrogen-containing alloy line feeding the first amount, perform the second line feeding operation when LF sets off with the nitrogen-containing alloy line feeding the second amount,
Wherein, in converter smelting step, the gas supply flow in smelting initial stage and tapping process is 120m
3/ h ~ 300m
3/ h, the gas supply flow smelted before mid-term to tapping is 300m
3/ h ~ 750m
3/ h,
Smelting mid-term, the gas supply flow after catch carbon is reduced to 120m
3/ h ~ 300m
3/ h, again with 300m after smelting for some time
3/ h ~ 750m
3the gas supply flow of/h performs re-blows to tapping.
2. method according to claim 1, wherein, the gas supply flow after terminating with tapping before starting blowing is 50m
3/ h ~ 80m
3/ h.
3. method according to claim 1, wherein, nitrogen-containing alloy line comprises the nitrogen of 4.5wt% ~ 7.5wt%.
4. method according to claim 3, wherein, in LF refinement step, the total amount of the nitrogen-containing alloy line that twice line feeding operation feeds altogether is 2m/ ton steel ~ 4.5m/ ton steel.
5. method according to claim 4, wherein, in the first line feeding operation, the nitrogen-containing alloy line of the first amount of feeding is 2m/ ton steel ~ 3.5m/ ton steel, and in the second line feeding operation, the nitrogen-containing alloy line of the second amount of feeding is 0m/ ton steel ~ 1m/ ton steel.
6. method according to claim 1, wherein, in converter smelting step, tapping terminates the Control of Nitrogen Content of rear molten steel at 45ppm ~ 50ppm.
7. method according to claim 1, wherein, in LF refinement step, after executing the first line feeding operation, the Control of Nitrogen Content of molten steel is at 90ppm ~ 100ppm.
8. method according to claim 1, wherein, in LF refinement step, after executing the second line feeding operation, the Control of Nitrogen Content of molten steel is at 100ppm ~ 120ppm.
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| CN110438292A (en) * | 2019-08-05 | 2019-11-12 | 凌源钢铁股份有限公司 | A kind of method of molten steel nitrogen pick-up in process for making |
| CN113416881A (en) * | 2021-06-15 | 2021-09-21 | 太原重工股份有限公司 | Accurate nitrogen control method in smelting of nitrogen-containing steel |
| CN116694851B (en) * | 2023-05-26 | 2024-04-05 | 福建三宝钢铁有限公司 | High-nitrogen process method for deformed steel bar |
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| JPH0686614B2 (en) * | 1990-02-14 | 1994-11-02 | 川崎製鉄株式会社 | Method for producing high nitrogen content steel in bottom blown or top blown converter |
| CN1038347C (en) * | 1994-08-03 | 1998-05-13 | 宝山钢铁(集团)公司 | Producing technology of low hydrogen high nitrogen steel |
| CN102383033B (en) * | 2011-11-08 | 2013-05-08 | 河北钢铁股份有限公司承德分公司 | 600-MPa grade vanadium-containing high-strength hot-rolled steel bar and production method thereof |
| CN102864279B (en) * | 2012-09-29 | 2014-08-27 | 莱芜钢铁集团有限公司 | Nitrogen adding method in process of LF (ladle furnace) refining |
| CN102828000A (en) * | 2012-10-08 | 2012-12-19 | 侯巍 | Metallurgical V-N microalloying and compound deoxidation cored wire |
| CN103451350B (en) * | 2013-08-13 | 2015-04-29 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for controlling nitrogen content in molten steel |
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