CN100567512C - A kind of nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device - Google Patents

A kind of nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device Download PDF

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CN100567512C
CN100567512C CNB2007100385292A CN200710038529A CN100567512C CN 100567512 C CN100567512 C CN 100567512C CN B2007100385292 A CNB2007100385292 A CN B2007100385292A CN 200710038529 A CN200710038529 A CN 200710038529A CN 100567512 C CN100567512 C CN 100567512C
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nitrogen
vacuum
vod
content
stainless steel
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CN101275174A (en
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李实�
蒋兴元
池和冰
顾学红
周武
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Baoshan Iron and Steel Co Ltd
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Abstract

The invention discloses a kind of nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device, this method is controlled to be nitrogen content greater than 1000ppm with the VOD initial condition, AOD terminal point carbon content is controlled to be 0.20～0.25%, and then in VOD vacuum-treat process, carry out decarburization, desulfurization charges into the operation of nitrogen, in the atmosphere adjusting stage, carry out the fine setting of nitrogen composition by bottom blowing nitrogen at last.Thereby in the time of can reaching VOD control endpoint carbon content＜250ppm, VOD terminal point nitrogen content can be realized stable control flexibly in 300～900ppm scope, solved in the VOD vacuum metling low-carbon (LC) control nitrogen type stainless steel process problem of dark decarburization and control nitrogen contradiction, for exploitation provides the otherwise effective technique assurance with nitrogen for the economical stainless steel of joint nickel of nickel.Reduced simultaneously the consumption of this type of steel grade smelting process argon gas, anti-material etc. again, the consumption of having saved the chromium nitride alloy, 120 yuan/ton of ton smelting steel cost savings.

Description

A kind of nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device
Technical field
The present invention relates to the stainless steel smelting technology, special relevant with VOD vacuum oxygen decarburization refining techniques.
Background technology
Along with global stainless steel production capacity promotes, nickel resources day is becoming tight, and each big stainless steel plant, the world develops one after another with the nickel-saving type stainless steel of nitrogen for nickel, and wherein 00Cr19Ni10 (being 304L) is exactly one of most typical steel grade, from the big condition of production, this type of steel grade is smelted and is had certain difficulty at present.There is following defective when for example, the two-step process path smelts this type of steel grade:
(1) since stainless steel smelting with the molten iron of cheapness as main raw material, cause the initial carbon content of AOD higher (＞3%), smelting cycle is long partially, so that rhythm of production is difficult to coupling, connects that to water the stove number on the low side;
(2) because endpoint carbon content requires＜0.025%, and AOD decarburization task is all relatively heavy, the consumption of various media and anti-material is all than higher.
Relative two step method, three-step approach is smelted this type of steel grade can shorten the AOD smelting cycle, faster production rhythm, and can reduce various energy medium consumption (as Ar), realize that smelting cost reduces.But concerning VOD, smelt this type of steel grade and also have a unmanageable problem of terminal point nitrogen content, mainly be because:
(1) according to normal VOD vacuum metling technology, if require control endpoint carbon content＜0.025%, then the VOD vacuum-treat finish nitrogen content must＜200ppm;
(2) owing to the restriction of ladle bottom blowing gas permeable brick, VOD ladle bottom blowing nitrogen flow is less relatively, so that limited by bottom blowing nitrogen nitrogen pick-up speed, if nitrogen increased amount is excessive, then smelting cycle is longer relatively;
(3) owing to causing the serious temperature drop of molten steel, so VOD is limited by the amplitude of bottom blowing nitrogen nitrogen pick-up by a large amount of nitrogen nitrogen pick-up of bottom blowing meeting.
Summary of the invention
The objective of the invention is in order to solve the unmanageable problem of VOD smelting low carbon control nitrogen type stainless steel nitrogen content, a kind of nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device is provided, it can realize endpoint carbon content less than 0.025%, and nitrogen content can be realized stable control flexibly in 300～900ppm scope.
For achieving the above object, the present invention is based on stainless steel refining VOD control nitrogen process thermodynamics and dynamic analysis, and each processing parameter is to the research of VOD control nitrogen influence, by special control to the whole vacuum metling process of VOD, in conjunction with go to the bottom nitrogen blowing microalloying operation of atmosphere, form a kind of new VOD control nitrogen technical scheme, concrete technical measures and controlled step are as follows:
One, control VOD initial carbon of supplied materials molten steel and nitrogen content, requiring initial carbon is 0.20～0.25%, initial nitrogen is greater than 1000ppm.
Because VOD vacuum decarburization process is accompanied by denitrogenation, and denitride amount becomes certain proportional relation with decarburized amount, so be necessary suitably to control the initial carbon content of VOD supplied materials molten steel; In addition, it is on the low side to finish the molten steel nitrogen content for fear of the VOD vacuum-treat, and preceding operation argon oxygen decarburizing furnace AOD can take omnidistance nitrogen flushing to smelt, and handles the preceding initial nitrogen content of molten steel to improve VOD.By research and practice, control VOD initial carbon content is 0.20～0.25%, initial nitrogen content is greater than 1000ppm the best, this carbon, nitrogen content scope can satisfy the requirement of VOD normal processing, can reduce the loss of nitrogen in the vacuum oxygen decarburization process and hitting of terminal point nitrogen content to greatest extent again.
Two, in VOD vacuum metling process, should follow following steps and requirement:
(1): the oxygen decarburization stage, after the VOD vacuum-treat begins, vacuum oxygen decarburization when vacuum tightness reaches 15 ~ 20kpa, CO content is to stop oxygen at 5 ~ 8% o'clock to the process waste gas.In order to solve low-carbon (LC) control nitrogen shaped steel kind VOD vacuum-treat stage decarburization and control nitrogen contradictory problems, at first reduce initial carbon content; Secondly should rationally control the vacuum oxygen decarburization time, i.e. control rationally stops oxygen constantly; According to decarburization thermodynamics and dynamic analysis, under guaranteeing that endpoint carbon content is less than 0.025% situation, the best oxygen that stops drops to 5 ~ 8% for the CO content in the waste gas constantly.
(2): free decarburization stage, CO, CO in the process waste gas 2Content was all reduced to 5% o'clock or dark vacuum strong mixing 10 ~ 12min can finish free decarburization.After the VOD oxygen blast stops, opening full pump and carry out the free decarburization of dark vacuum.Because the free decarburization of VOD is to carry out dark vacuum strong mixing to handle under no slag situation, so denitrogenation speed is relatively big; At this type of steel grade, should shorten free decarburization time as far as possible, reduce the loss of free decarburization stage nitrogen.CO, CO in the process waste gas 2Content was all reduced to 5% o'clock or dark vacuum strong mixing 10 ~ 12min can finish free decarburization.
(3): in the reinforced stage, before adding reductive agent ferrosilicon and slag charge, charge into nitrogen in the vacuum tank and press again.Nitrogen forms saturated nitrogen atmosphere after entering vacuum tank above molten steel surface, carry out the operation of strong mixing Argon simultaneously, and the promotion molten steel fully contacts with nitrogen, and the realization molten steel is inhaled nitrogen by a small margin.
(4): in the reduction and desulfurization stage, the reinforced end continues dark vacuum strong mixing reduction and desulfurization, keeps 5 ~ 10min.Because molten steel oxygen position, reduction back descends, and sweetening process takes dark vacuum strong mixing operation, so stage denitrogenation speed is also bigger.In order to reduce the loss of desulfurization stage nitrogen, should shorten dark vacuum reducing desulfurization time equally as far as possible, dark vacuum strong mixing desulfurization 5 ~ 10min can finish after promptly slag charge fully melted.
(5): the vacuum breaker stage, carry out vacuum breaker by nitrogen, continue to take the argon gas strong mixing in the vacuum breaker process, vacuum breaker finishes the back and continues to keep Argon to stir 3 ~ 5min, presses again as reinforced initial vacuum and realizes that molten steel inhales nitrogen by a small margin.
Three, bottom blowing nitrogen microalloying is handled
Finish back molten steel analysis of nitrogen content result according to the VOD vacuum-treat, under atmospheric condition, substitute chromium nitride and carry out the fine setting of nitrogen component, require under airtight environment, to carry out, to improve nitrogen pick-up efficient by bottom blowing nitrogen.
In the above-mentioned steps two (3) described, after free decarburization finishes,, vacuum tightness should be returned to behind 6 ~ 12kpa reinforced in order to prevent reinforced process splash.
In the above-mentioned steps three, the bottom blowing nitrogen flow is controlled at not serious exposed being advisable of molten steel, and the nitrogen flushing amount can be calculated according to the deviation of actual nitrogen content and target nitrogen content.
Nitrogen nitrogen pick-up coefficient is roughly 800～1000ppm/m in the above-mentioned steps three 3T).
The present invention makes it compared with prior art owing to adopted above technical scheme, has the following advantages and positively effect:
1. dark decarburization and control nitrogen contradictory problems that VOD vacuum metling low-carbon (LC) control nitrogen type stainless steel faces have been solved effectively, guaranteeing under the situation of VOD endpoint carbon content less than 250ppm that promptly VOD terminal point nitrogen content can be realized stable control flexibly in 300～900ppm scope.
2. after this control nitrogen method is implemented, reduced the consumption of this type of steel grade smelting process argon gas, anti-material etc., and the consumption of having saved the chromium nitride alloy, 120 yuan/ton of ton smelting steel cost savings.
Embodiment:
Embodiment 1:
Steel grade: 00Cr19Ni10;
1, VOD molten steel initial condition
(1) initial carbon content: 0.202%
(2) initial nitrogen content: 0.217%
(3) molten steel amount: 113t
2, VOD vacuum-treat actual achievement
(1) oxygen decarburization stops constantly: CO content 7.5% in the waste gas
(2) oxygen decarburization time: 24min
(3) free decarburization finish time: CO content 4.2% in the waste gas, CO 2Content 4.8%;
(4) free decarburization time: 9min
(5) reduction and desulfurization time: 6min
3, nitrogen microalloying actual achievement
(1) bottom blowing nitrogen: 40.6m 3
(2) nitrogen flushing flow, nitrogen flushing time: 90m 3/ h, 28min
4, composition actual achievement
(1) steel sample analysis
Element C Si Mn S P Cr Ni N
The VOD vacuum is initial 0.202 0.04 1.07 0.008 0.02 18.05 8.01 0.217
The VOD vacuum ends 0.021 0.25 1.11 0.008 0.02 18.12 8.17 0.071
VOD handles end of a period 0.02 0.38 1.10 0.009 0.02 18.03 8.04 0.061
Finished product 0.019 0.37 1.11 0.008 0.021 18.19 8.19 0.068
(2) the gas sample is analyzed
Element C S O N
The VOD vacuum ends 0.015 0.008 0.007 0.043
VOD handles end of a period 0.017 0.008 0.011 0.055
Finished product 0.0196 0.008 0.0172 0.0582
Embodiment 2:
Steel grade: 00Cr19Ni10;
1, VOD molten steel initial condition
(1) initial carbon content: 0.258%
(2) initial nitrogen content: 0.093%
(3) molten steel amount: 110.2t;
2, VOD vacuum-treat actual achievement
(1) oxygen decarburization stops constantly: CO content 6.8% in the waste gas
(2) oxygen decarburization time: 26min
(3) free decarburization finish time: CO content 3.2% in the waste gas, CO 2Content 4.5%;
(4) free decarburization time: 8min
(5) reduction and desulfurization time: 8min
3, nitrogen microalloying actual achievement
(1) bottom blowing nitrogen: 25.4m 3
(2) nitrogen flushing flow, nitrogen flushing time: 90m 3/ h, 16min
4, composition actual achievement
(1) steel sample analysis
Element C Si Mn S P Cr Ni N
The VOD vacuum is initial 0.248 0.04 1.10 0.005 0.018 18.05 8.09 0.093
The VOD vacuum ends 0.02 0.53 1.09 0.002 0.019 17.88 8.08 0.059
VOD handles end of a period 0.028 0.51 1.12 0.002 0.018 18.17 8.20 0.062
Finished product 0.022 0.47 1.10 0.002 0.02 18.19 8.07 0.060
(2) the gas sample is analyzed
Element C S O N
The VOD vacuum ends 0.0166 0.002 0.0436 0.0555
VOD handles end of a period 0.0156 0.001 0.0047 0.0556
Finished product 0.016 0.002 0.0059 0.0584
Embodiment 3:
Steel grade: 00Cr19Ni10;
Molten steel amount: 118.4t
1, VOD molten steel initial condition
(1) initial carbon content: 0.228%
(2) initial nitrogen content: 0.115%
2, VOD vacuum-treat actual achievement
(1) oxygen decarburization stops constantly: CO content 8% in the waste gas
(2) oxygen decarburization time: 24min
(3) free decarburization finish time: CO content 2.8% in the waste gas, CO 2Content 4.2%;
(4) free decarburization time: 12min
(5) reduction and desulfurization time: 10min
3, nitrogen microalloying actual achievement
(1) bottom blowing nitrogen: 15m 3
(2) nitrogen flushing flow, nitrogen flushing time: 90m 3/ h, 11min
4, composition actual achievement
(1) steel sample analysis
Element C Si Mn S P Cr Ni N
The VOD vacuum is initial 0.228 0.05 1.18 0.006 0.021 17.89 8.03 0.115
The VOD vacuum ends 0.02 0.51 1.11 0.003 0.02 17.83 8.08 0.056
VOD handles end of a period 0.022 0.49 1.12 0.003 0.021 18.09 8.04 0.065
Finished product 0.019 0.48 1.14 0.003 0.020 18.22 8.18 0.064
(2) the gas sample is analyzed
Element C S O N
The VOD vacuum ends 0.0196 0.003 0.0058 0.0510
VOD handles end of a period 0.0210 0.003 0.0065 0.0624
Finished product 0.0185 0.002 0.0062 0.0622
Embodiment 4:
Steel grade: 00Cr19Ni10;
1, VOD molten steel initial condition
(1) initial carbon content: 0.212%
(2) initial nitrogen content: 0.127%
(3) molten steel amount: 108t
2, VOD vacuum-treat actual achievement
(1) oxygen decarburization finish time: CO content 5% in the waste gas
(2) oxygen decarburization time: 26min
(3) free decarburization finish time: CO content 3.2% in the waste gas, CO 2Content 4.3%;
(4) free decarburization time: 12min
(5) reduction and desulfurization time: 8min
3, nitrogen microalloying actual achievement
(1) bottom blowing nitrogen: 22.5m 3
(2) nitrogen flushing flow, nitrogen flushing time: 90m 3/ h, 16min
4, composition actual achievement
(1) steel sample analysis
Element C Si Mn S P Cr Ni N
The VOD vacuum is initial 0.248 0.05 1.04 0.004 0.025 18.15 8.15 0.127
The VOD vacuum ends 0.022 0.41 1.04 0.004 0.024 18.12 8.12 0.046
VOD handles end of a period 0.022 0.38 1.05 0.003 0.025 18.13 8.10 0.056
Finished product 0.023 0.39 1.03 0.003 0.025 18.10 8.13 0.054
(2) the gas sample is analyzed
Element C S O N
The VOD vacuum ends 0.0202 0.004 0.0059 0.0436
VOD handles end of a period 0.0218 0.003 0.0067 0.0542
Finished product 0.0220 0.002 0.0072 0.0532
Embodiment 5:
Steel grade: 00Cr19Ni10;
1, VOD molten steel initial condition
(1) initial carbon content: 0.243%
(2) initial nitrogen content: 0.126%
(3) molten steel amount: 109.5t;
2, VOD vacuum process control actual achievement
(1) oxygen decarburization stops constantly: CO content 8% in the waste gas
(2) oxygen decarburization time: 25min
(3) free decarburization finish time: CO content 4.6% in the waste gas, CO 2Content 5.0%;
(4) free decarburization time: 8min
(5) reduction and desulfurization time: 5min
3, nitrogen microalloying actual achievement
(1) bottom blowing nitrogen: 28m 3
(2) nitrogen flushing flow, nitrogen flushing time: 90m 3/ h, 18min
4, composition actual achievement
(1) steel sample analysis
Element C Si Mn S P Cr Ni N
The VOD vacuum is initial 0.243 0.04 1.14 0.004 0.023 18.15 8.03 0.126
The VOD vacuum ends 0.019 0.45 1.12 0.003 0.022 17.88 8.04 0.042
VOD handles end of a period 0.020 0.46 1.13 0.002 0.023 18.17 8.02 0.058
Finished product 0.020 0.45 1.10 0.002 0.023 18.19 8.01 0.060
(2) the gas sample is analyzed
Element C S O N
The VOD vacuum ends 0.0170 0.003 0.0067 0.0400
VOD handles end of a period 0.0185 0.002 0.0062 0.0564
Finished product 0.0190 0.002 0.0058 0.0553

Claims (4)

1. nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device is characterized in that comprising:
Step 1: control VOD initial carbon of supplied materials molten steel and nitrogen content, initial carbon is 0.20～0.25%, initial nitrogen is greater than 1000ppm;
Step 2: VOD vacuum metling process
(1) the oxygen decarburization stage, CO content is to stop oxygen at 5 ~ 8% o'clock in the process waste gas;
(2) the free decarburization stage, CO, CO in the process waste gas 2Content was all reduced to 5% o'clock or dark vacuum strong mixing 8 ~ 12min can finish free decarburization;
(3) in the reinforced stage, add before reductive agent ferrosilicon and the slag charge, charge into nitrogen in the vacuum tank and press again, nitrogen forms saturated nitrogen atmosphere after entering vacuum tank above molten steel surface, carry out the operation of strong mixing Argon simultaneously, the promotion molten steel fully contacts with nitrogen, and the realization molten steel is inhaled nitrogen by a small margin;
(4) the reduction and desulfurization stage, 5 ~ 10min is kept in dark vacuum strong mixing;
(5) the vacuum breaker stage charges into the nitrogen vacuum breaker, and takes the argon gas strong mixing, and the multiple fully back of pressing continues to keep Argon to stir 3 ~ 5min;
Step 3: bottom blowing nitrogen microalloying is handled, and finishes back molten steel analysis of nitrogen content result according to the VOD vacuum-treat, carries out the fine setting of nitrogen component under atmospheric condition, in airtight environment.
2. nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device as claimed in claim 1 is characterized in that: step 2 returns to 6 ~ 12kpa with vacuum tightness in (3).
3. nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device as claimed in claim 2, it is characterized in that: the bottom blowing nitrogen flow is controlled at not serious exposed being advisable of molten steel in the step 3, and the nitrogen flushing amount can be calculated according to actual nitrogen content and target nitrogen content deviation.
4. nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device as claimed in claim 3 is characterized in that: nitrogen nitrogen pick-up coefficient is 800～1000ppm/m in the step 3 3T.
CNB2007100385292A 2007-03-27 2007-03-27 A kind of nitrogen content control method for smelting stainless steel by vacuum oxygen decarburization device Expired - Fee Related CN100567512C (en)

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CN102199688B (en) * 2010-03-25 2013-02-06 宝山钢铁股份有限公司 Method for efficiently refining ultra-pure ferritic stainless steel
CN102251076B (en) * 2010-05-21 2013-04-03 宝山钢铁股份有限公司 RH vacuum refining method of ultra-low carbon stainless steel
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CN112126745A (en) * 2020-09-27 2020-12-25 江油市长祥特殊钢制造有限公司 Nitrogen increasing method for stainless steel

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