CN102041443A - Low-alloy Q345D-Z25 medium plate and production process thereof - Google Patents
Low-alloy Q345D-Z25 medium plate and production process thereof Download PDFInfo
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Abstract
The invention discloses a low-alloy Q345D-Z25 medium plate and a production process thereof. The low-alloy Q345D-Z25 medium plate comprises the following chemical components in percentage by weight: 0.13-0.18% of C, 0.20-0.45% of Si, 1.30-1.60% of Mn, less than or equal to 0.018wt% of P, less than or equal to 0.007% of S, 0.015-0.050% of Als, and the balance of Fe and residual elements. The process disclosed by the invention comprises the following steps: KR (knotted reactor) hot metal pretreatment of high-quality hot metal, processing with a top-bottom combined blowing converter, LF ((ladle furnace) refining, vacuum degassing process, casting blank stack cooling, processing with a heating furnace, rolling, ACC (accelerated cooling) laminar flow cooling, processing with a hot straightener, stack cooling, finishing, external inspection, flaw detection and storage. The invention has the beneficial effects that: compared with the traditional Q345DD-Z25, precious alloys such as Nb, Ti and the like are not added without changing the carbon equivalent, all performance indexes of Q345D-Z25 are assured to meet the requirements of national standard, and the production cost is remarkably reduced.
Description
Technical field
The invention belongs to the Heavy Plate Production technical field, be specifically related to a kind of employing and do not add microalloy element production low-alloy Q345D-Z25 steel plate and production technique thereof.
Background technology
Current international financial crisis has caused bigger impact to Iron and Steel Enterprises in China; the plate of moderate thickness industry of steel mill period at a low ebb always particularly; for tackling the disadvantageous effect that international financial crisis brings; accelerate restructuring; promote industrial upgrading; realize low cost strategy, strengthen enterprise competitiveness and have a very important role.At present, domestic production low-alloy Q345D-Z25 steel plate producer is few, because it in process of production, adds microalloy elements such as Nb, Ti, the production cost height; Complex process.
Summary of the invention
Disadvantageous effect for the reply international financial crisis brings realizes low cost strategy, strengthens enterprise competitiveness.The present invention has obtained a kind of technology of not adding any microalloy element production low-alloy Q345D-Z25 steel plate, thereby has finished the present invention through groping.
Therefore, the object of the present invention is to provide a kind of low-cost Q345D-Z25 steel plate.
Another object of the present invention is to provide a kind of production technique of the Q345D-Z25 of reducing production costs steel plate.
For achieving the above object, the technical scheme that the present invention takes is: this low-alloy Q345D-Z25 steel plate comprise following chemical components in mass percent (unit, wt%): C:0.13～0.18, Si:0.20～0.45, Mn:1.30～1.60, P≤0.018, S≤0.007, Als:0.015～0.050, other is Fe and relict element;
Carbon equivalent [Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15] :≤0.44.
In the preceding method, the steel plate thickness of being produced is 80mm and following specification.
For obtaining above-mentioned steel plate, the technical process that the present invention adopts is: high-quality molten iron, KR hot metal pretreatment, top and bottom combined blown converter, the refining of LF stove, vacuum outgas processing, strand cooling in heap, process furnace, rolling, ACC laminar flow cooling, thermal straightening machine, cooling in heap, finishing, outer inspection, flaw detection, warehouse-in, in described rolling step, the recrystallize final temperature of steel is 895 ℃, the steel gauge control of drying in the air is at 2.2～3 times of finished product thickness, when rolled piece temperature≤880 ℃, the beginning subordinate phase is rolling, two-stage accumulative total deformation rate 〉=60%, finishing temperature is controlled at 780～820 ℃; The rolling back that finishes adopts the ACC control cold, and final cooling temperature is controlled between 640～680 ℃, is sent to the straightener aligning then; In the cooling in heap step, the stacking slow cooling temperature is not less than 400 ℃, cooling in heap time 〉=24 hour.
The present invention is on the composition basis of original Q345D-Z25 low alloy steel, suitably adjust the content composition and division in a proportion example of C, Mn among the Q345D-Z25, and P, S etc. influence the harmful element content of steel plate plasticity and toughness in the simultaneously strict control steel, and then do not add price high microalloy element Nb, Ti etc., thereby guaranteed the ballistic work of Q345D-Z25 steel plate, guaranteed the intensity and the plasticity coupling of steel plate simultaneously again.
In smelting process, P(phosphorus in the strict control steel), S(sulphur) wait harmful element, the purity of assurance molten steel reaches the Clean Steel level substantially.In follow-up rolling heat-processed, thick for preventing inside steel billet crystal grain, suitably reduce Heating temperature, avoid the inside steel billet original austenite grains too to grow up, be the refinement establish a firm foundation of steel billet crystal grain in the operation of rolling.In the operation of rolling,, can guarantee Q345D-Z25 plate property demand by adopting domestic advanced person's TMCP rolling technique.
Beneficial effect of the present invention is: compare with traditional Q345D-Z25, under the constant situation of carbon equivalent, do not add valuable alloys such as Nb, Ti, guarantee the requirement that is up to state standards of the every performance index of Q345D-Z25, greatly reduce production cost.
Embodiment
Low-alloy Q345D-Z25 steel plate of the present invention comprise following chemical components in mass percent (unit, wt%): C:0.13～0.18, Si:0.20～0.45, Mn:1.30～1.60, P≤0.018, S≤0.007, Als:0.015～0.050, other is Fe and relict element;
Carbon equivalent [Ceq=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15] :≤0.44.
In the preceding method, the steel plate thickness of being produced is 80mm and following specification.
For obtaining above-mentioned steel plate, the technical process that the present invention adopts is: high-quality molten iron, KR hot metal pretreatment, top and bottom combined blown converter, the refining of LF stove, vacuum outgas processing, strand cooling in heap, process furnace, rolling, ACC laminar flow cooling, thermal straightening machine, cooling in heap, finishing, outer inspection, flaw detection, warehouse-in, in described rolling step, the recrystallize final temperature of steel is 895 ℃, the steel gauge control of drying in the air is at 2.2～3 times of finished product thickness, when rolled piece temperature≤880 ℃, the beginning subordinate phase is rolling, two-stage accumulative total deformation rate 〉=60%, finishing temperature is controlled at 780～820 ℃; The rolling back that finishes adopts the ACC control cold, and final cooling temperature is controlled between 640～680 ℃, is sent to the straightener aligning then; In the cooling in heap step, the stacking slow cooling temperature is not less than 400 ℃, cooling in heap time 〉=24 hour.
The present invention adopts converter smelting, continuous casting, and the rolling method of 3800m wide and heavy plate mill is produced the Q345D-Z25 Low Alloy Steel Plate.Its technical process is: high-quality molten iron, KR hot metal pretreatment, 100/120 ton of top and bottom combined blown converter, the refining of LF stove, vacuum outgas processing, strand cooling in heap 24-60 hours, pusher-type furnace, 3800m milling train, the cooling of ACC laminar flow, 11 roller thermal straightening machines, cooling in heap, finishing, outer inspection, flaw detection, warehouse-in.
Embodiment is as follows:
1, composition design
On the composition basis of traditional Q 345D-Z25 low alloy steel, smelt by Clean Steel, strict control P, S content do not add microalloy Nb, Ti, by carrying out strict rolling low-carbon-equivalent and the weldability that had both guaranteed steel plate of TMCP, ensure Q345D-Z25 obdurability coupling again.
Concrete composition design is as follows:
C:0.13～0.18%, Si:0.20～0.45%, Mn:1.30～1.60%, P: S≤0.018% :≤0.007%, AlS:0.015～0.050%, other is Fe and relict element;
2, KR hot metal pretreatment technology
Before the molten iron that arrives at a station must be taken off slag with take off the back slag, guarantee liquid level thickness of slag layer≤20mm, molten iron guarantees molten iron S≤0.005% after the KR stirring desulphurization, assurance desulfurization cycle≤21min, desulfurization temperature drop≤20 ℃.
, converter smelting process
Go into stove molten iron S≤0.005%, P≤0.080%, molten iron temperature 〉=1270 ℃, molten iron Intake Quantity error is controlled by ± 1t, the strict high-quality scrap stock that adopt of steel scrap, process rifle position is by early stage 1.0-1.3m, mid-term 1.2-1.6m, later stage 1.0-1.1m control, slag making basicity R presses 2.5-4.0 control, tapping target P≤0.015%, C 〉=0.05%, S≤0.012%, in the tapping process in ladle Si-Al-Ba-Ca, manganeseirom, ferro-silicon and lime, fluorite.With slag tapping before the floating plug retaining, adopt the slag stop cone pushing off the slag before tapping finishes before the tapping, guarantee thickness of slag layer≤30mm, require omnidistance Argon in the converter tapping process.
, argon blowing process
The disposable adding aluminum steel in argon station requires strong Argon 3min at the argon station, flow 200-500NL/min, and molten steel face bore hole diameter is controlled at 300～500mm, must not be lower than 1570 ℃ from argon station temperature.
, the LF refinery practice
Omnidistance Argon in the refining process, Argon intensity is regulated according to different link needs.
Add refining slag, basicity press 4.0-6.0 and is controlled, and the refinement and deoxidation agent is based on calcium carbide, aluminum shot, ferrosilicon powder, and add-on is according to oxygen level in the molten steel and make the white slag situation and add in right amount.Heat-processed selects suitable electric current to heat according to rhythm is more than needed with temperature conditions, heat-up time, one heating 7-12min, two heating 6-10min required in two heat-processedes according to the slag making situation by twice control, add reductor, and require the dry slag number of times greater than 6 times.Add silicon-calcium wire before leaving from station, must close argon gas, 1565 ± 15 ℃ of last steel temperature (not adopting vacuum outgas)/1610 ± 15 ℃ (employing vacuum outgas) before adding silicon-calcium wire.
, the VD refinery practice
VD vacuum tightness must reach below the 67Pa, and the dwell time is necessary 〉=15min, soft blow 2-5min or do not blow behind the vacuum breaker, and molten steel must not expose in the soft blow process.The normal online bag pumpdown time: (vacuumizing preceding liquid steel temperature-target temperature leaving from station)/1.7min.Insulating covering agent guarantees to be paved with the molten steel face, must close argon gas, 1565 ± 15 ℃ of last steel temperature before adding insulating covering agent.
, continuous casting process
Guarantee that the casting machine status of equipment is good before watering steel; 15 ± 10 ℃ of middle bag superheating temperature; pulling rate: 0.7m/min; specific water: 0.80L/ ㎏; electricity stirs: 900A, 5Hz, 30s-3-30s; continuous-casting steel pouring requires the whole process protection casting, unwraps greatly and waters necessary cover protective tube in the 1min of back, must guarantee not show of molten steel face in the middle bag casting process.Rationally control stopper Argon amount in the steel pouring process, guarantee that liquid level fluctuation of crystallizer is slight.After rolling off the production line, strand requires cooling in heap 〉=12h.
, the heating
Heating temperature and heat-up time are as follows: 900-1000 ℃ of preheating section temperature, 1220-1240 ℃ of heating zone temperature, 1200-1220 ℃ of holding-zone temperature, rate of heating 10-13min/cm;
9, controlled rolling and controlled cooling:
In conjunction with the steel-making chemical ingredients, through theoretical calculation, the recrystallize final temperature of steel is 895 ℃, and is thick for preventing mixed crystal and crystal grain, therefore designs it and treats that temperature is dried in the air and begin finish rolling below the steel to 880 ℃.The steel gauge control of drying in the air at the 2.2-3 of finished product thickness doubly, for finish rolling stage accumulative total deflection and crystal grain thinning, dislocations strengthening lay the foundation;
Easily make grain growth owing to roll the back slow cooling, and the alloy solid solution amounts such as C, Mn in the tissue are limited, therefore will control suitable speed of cooling.In order to obtain good comprehensive mechanical property, according to the difference of thickness of slab, roll the back and adopt different laminar flow coolings, by adjusting cooling manifold group number, guarantee to return red temperature between 640～680 ℃.
Cooling controlling and rolling controlling process is as follows:
The fs start rolling temperature is controlled between 1000～1200 ℃, and it is rolling to adopt high temperature low speed to depress greatly, and reduction in pass is not less than 20mm; When temperature is not less than 1000 ℃, stop rolling the steel that dries in the air, the steel thickness that dries in the air is 2.2-3 times of finished product thickness; When rolled piece temperature≤880 ℃, the beginning subordinate phase is rolling, two-stage accumulative total deformation rate 〉=60%, and finishing temperature is controlled at 780～820 ℃; The rolling back that finishes adopts the ACC control cold, and final cooling temperature is controlled between 640～680 ℃, is sent to the straightener aligning then.
, cooling in heap technology
Adopt high temperature cooling in heap technology can effectively avoid to reduce the content of hydrogen in the steel plate simultaneously greatly, fully realize thermal diffusion effect, improve the steel plate inspection defective because of cooling off the unrelieved stress that produces fast.Steel plate stacking slow cooling technology is as follows; The stacking slow cooling temperature is not less than 400 ℃, cooling in heap time 〉=24 hour;
11, interpretation of result
11.1 mechanical mechanics property analysis
Composition and mechanical mechanics property press GB/T1591-2008 and GB5313-85 carries out, and mechanical property specifically sees Table 1.
Table 1 Q345D-Z25 steel plate mechanical mechanics property
The thick Q345D-Z25 of this trial production 20-80mm amounts to 50 batches, and wherein: yield strength is controlled at 340～420 MPa, has on average reached 365 MPa, than the rich 30MPa of standard; Tensile strength is controlled at 510～620 MPa, has on average reached 546 MPa, than the rich 56MPa of standard; Elongation is controlled at 25%～32%, on average reaches 28%, than standard affluence 7%;-20 ℃ of V-type ballistic works are controlled at 150～320J, have on average reached 210 J, and Z is controlled between 25%～45% to stretching, on average reach 32%, reach the level of Q345D-Z25 fully.
Outer inspection and flaw detection
The steel plate of being developed is examined outward, and the percentage of A-class goods 100% is detected a flaw by JB/T 47030, and unification level rate is 80%, and closing three grades of rates is 100%, has reached desired result.
Claims (2)
1. low-alloy Q345D-Z25 steel plate, this low-alloy Q345D-Z25 steel plate comprises following chemical components in mass percent, and (unit, wt%): C:0.13～0.18, Si:0.20～0.45, Mn:1.30～1.60, P≤0.018, S≤0.007, Als:0.015～0.050, other is Fe and relict element.
2. production technique of low-alloy Q345D-Z25 steel plate according to claim 1, this technology may further comprise the steps: the high-quality molten iron, the KR hot metal pretreatment, top and bottom combined blown converter, the refining of LF stove, vacuum outgas is handled, the strand cooling in heap, process furnace, rolling, the cooling of ACC laminar flow, thermal straightening machine, cooling in heap, finishing, outer inspection, flaw detection, warehouse-in, it is characterized in that in described rolling step, the recrystallize final temperature of steel is 895 ℃, the steel gauge control of drying in the air is at 2.2～3 times of finished product thickness, when rolled piece temperature≤880 ℃, the beginning subordinate phase is rolling, two-stage accumulative total deformation rate 〉=60%, finishing temperature is controlled at 780～820 ℃; The rolling back that finishes adopts the ACC control cold, and final cooling temperature is controlled between 640～680 ℃, is sent to the straightener aligning then; In the cooling in heap step, the stacking slow cooling temperature is not less than 400 ℃, cooling in heap time 〉=24 hour.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102329913A (en) * | 2011-07-08 | 2012-01-25 | 南阳汉冶特钢有限公司 | Method for reducing micro cracks on surface of steel plate |
| CN103451520A (en) * | 2013-09-25 | 2013-12-18 | 武汉钢铁(集团)公司 | Q345 engineering steel and production method thereof |
| CN103602885A (en) * | 2013-10-22 | 2014-02-26 | 内蒙古包钢钢联股份有限公司 | Low-alloy and high-strength steel plate and production method thereof |
| CN103627951A (en) * | 2013-12-06 | 2014-03-12 | 马钢(集团)控股有限公司 | High-toughness boracic carbon structural steel plate roll and production method thereof |
| CN104018063A (en) * | 2014-06-18 | 2014-09-03 | 内蒙古包钢钢联股份有限公司 | Low alloy and high strength Q420C medium steel plate and production method thereof |
| CN104018060A (en) * | 2014-05-23 | 2014-09-03 | 内蒙古包钢钢联股份有限公司 | Guaranteed crack detection and guaranteed performance Q345B steel plate with thickness of 150mm and production method thereof |
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| CN101871083A (en) * | 2010-06-14 | 2010-10-27 | 南阳汉冶特钢有限公司 | Ultra-thick low-alloy high-strength Q345-series steel plate and production method thereof |
| CN101876000A (en) * | 2009-11-18 | 2010-11-03 | 秦皇岛首秦金属材料有限公司 | Method for producing high-toughness ultra-thick plate by using continuous casting blank |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101876000A (en) * | 2009-11-18 | 2010-11-03 | 秦皇岛首秦金属材料有限公司 | Method for producing high-toughness ultra-thick plate by using continuous casting blank |
| CN101871083A (en) * | 2010-06-14 | 2010-10-27 | 南阳汉冶特钢有限公司 | Ultra-thick low-alloy high-strength Q345-series steel plate and production method thereof |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102329913A (en) * | 2011-07-08 | 2012-01-25 | 南阳汉冶特钢有限公司 | Method for reducing micro cracks on surface of steel plate |
| CN103451520A (en) * | 2013-09-25 | 2013-12-18 | 武汉钢铁(集团)公司 | Q345 engineering steel and production method thereof |
| CN103602885A (en) * | 2013-10-22 | 2014-02-26 | 内蒙古包钢钢联股份有限公司 | Low-alloy and high-strength steel plate and production method thereof |
| CN103627951A (en) * | 2013-12-06 | 2014-03-12 | 马钢(集团)控股有限公司 | High-toughness boracic carbon structural steel plate roll and production method thereof |
| CN104018060A (en) * | 2014-05-23 | 2014-09-03 | 内蒙古包钢钢联股份有限公司 | Guaranteed crack detection and guaranteed performance Q345B steel plate with thickness of 150mm and production method thereof |
| CN104018063A (en) * | 2014-06-18 | 2014-09-03 | 内蒙古包钢钢联股份有限公司 | Low alloy and high strength Q420C medium steel plate and production method thereof |
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Application publication date: 20110504 |