CN103042039B - Controlled rolling and cooling process for Cr-containing economic X70 pipeline hot-rolled steel coil plate - Google Patents
Controlled rolling and cooling process for Cr-containing economic X70 pipeline hot-rolled steel coil plate Download PDFInfo
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- CN103042039B CN103042039B CN201310001803.4A CN201310001803A CN103042039B CN 103042039 B CN103042039 B CN 103042039B CN 201310001803 A CN201310001803 A CN 201310001803A CN 103042039 B CN103042039 B CN 103042039B
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Abstract
The invention discloses a controlled rolling and cooling process for a Cr-containing economic X70 pipeline hot-rolled steel coil plate. The controlled rolling and cooling process for the Cr-containing economic X70 pipeline hot-rolled steel coil plate is characterized by including the steps: (1) soaking at the heating temperature of 1150-1210 DEG C for not shorter than 120 minutes; (2) distributing rough rolling passes and using 8-10 passes for rough rolling, wherein deformation of each pass is required to be within the range of 10%-20%, and deformation of the last three rough rolling passes is within the range of 10%-20%; (3) distributing finish rolling passes, wherein the rolling temperature of the first pass of finish rolling is not higher than 1050 DEG C, the deformation of the last finish rolling pass is less than 8%, the accumulated deformation of the last two passes is less than 16%, the temperature of final finish rolling ranges from 770 DEG C to 850 DEG C; (4) immediately implementing laminar cooling at the cooling speed higher than 20-25 DEG C/s after finish rolling; and (5) after laminar cooling, coiling to the coil plate via a coiling machine at the coiling temperature of 300-400 DEG C.
Description
Technical field
The invention belongs to pipe line steel production technical field, particularly the cooling controlling and rolling controlling process of X70 line steel hot rolling coiled sheet.
Background technology
Domestic and international production X70 pipe line steel generally adopts that ' Composition Design of Nb+Mo ', to obtain acicular ferrite structure; On the one hand obtain higher low-temperature impact toughness, on the other hand, reduce Bauschinger effect, that is, reduce the decline of material yield strength performance after tubulation.In fact, in the industrial production of X70 pipe line steel, even if adopt molybdenum element also can not can obtain uniform acicular ferrite structure completely, the generation of Bauschinger effect also cannot be avoided completely.Time serious, the matrix of X70 pipe line steel coiled sheet is the line and staff control of the ferrite of polygon form, granular bainite and a small amount of acicular ferrite, and the drop-out value of yield strength, close to 100MPa, makes the yield strength of X70 steel pipe be near or below lower limit 485MPa before and after coiled sheet tubulation.In addition, molybdenum element is adopted in the manufacture of X70 coiled sheet, although polygonal ferrite can be suppressed to be formed, be more convenient for obtaining acicular ferrite structure, make manufacturing process simple and direct feasible, but the shortcoming of this way also clearly, in steel, often add the molybdenum of 0.10%, improve ton steel production cost 220 ~ 250 yuan.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of cooling controlling and rolling controlling process containing Cr economical X 70 pipeline steel hot-rolling coiled sheet, when meeting X70 line steel hot rolling coiled sheet performance, significantly reduces production cost.
For solving the problems of the technologies described above, the invention provides a kind of cooling controlling and rolling controlling process containing Cr economical X 70 pipeline steel hot-rolling coiled sheet, it is characterized in that, the chemical component weight percentage (%) of described coiled sheet is: C 0.05-0.075%, Si 0.10%-0.35%, Mn 1.00-1.65%, Nb 0.050-0.080%, Ti 0.010-0.025%, Cr 0.30-0.4%, surplus is iron and inevitable impurity; The cooling controlling and rolling controlling process of described coiled sheet is:
(1) heating-up temperature 1150 ~ 1210 DEG C, soaking time is no less than 120 minutes,
(2) roughing rolling pass is distributed: use 8 ~ 10 passage roughing, and every time deflection requires between 10 ~ 20%, the deflection 17-20% of last 3 passages of roughing,
(3) finish rolling rolling pass is distributed: finish rolling first passage rolling temperature is not higher than 1050 DEG C, and last pass deformation of finish rolling is less than 8%, and last two passage cumulative deformations are less than 16%, finish rolling finishing temperature 770 DEG C-850 DEG C,
(4) implement section cooling immediately after finish rolling, cooldown rate is greater than 20-25 DEG C/s,
(5) after section cooling, coiled sheet is coiled into through coiling machine, coiling temperature 300-400 DEG C.
Design philosophy of the present invention is:
Technical scheme of the present invention has following three main points: (1) adopts low-carbon (LC) Composition Design, carries out Nb-microalloying, adds the chromium element being more than or equal to 0.30%; (2) target is to obtain evenly tiny acicular ferrite structure, containing a small amount of granular bainite microstructure, to improve obdurability; (3) smelted by super clean and reduce S, P, N content to greatest extent, reduce the Grain Boundary Segregation of manganese sulfide inclusion and phosphorus to improve low-temperature impact work further.The present invention is not containing elements such as molybdenum, nickel, copper, vanadium.
The controlled rolling of X70 pipe line steel of the present invention and the process system of controlled cooling model are:
(1) heating-up temperature 1150 ~ 1210 DEG C, soaking time is no less than 120 minutes.
(2) roughing rolling pass is distributed: use 8 ~ 10 passage roughing.Every time deflection requires between 10 ~ 20%.In order to fining austenite grains, the deflection of last 3 passages of roughing requires close to 20%; For avoiding roll-force excessive, the deflection of last 3 passages of roughing requires to be not more than 20%.
(3) finish rolling rolling pass is distributed: use hot continuous rolling.Finish rolling first passage rolling temperature is not higher than 1050 DEG C.Require that last pass deformation of finish rolling is less than 8%, last two passage cumulative deformations are less than 16%.Finish rolling finishing temperature, not higher than 850 DEG C, is not less than 770 DEG C.Adopt TMCP thermomechanical controlled rolling technique, do not allow arbitrary frame not depress empty mistake, also do not adopt HTP high temperature rolling technique.
(4) section cooling is implemented immediately after finish rolling.The technological measure specially increased without other between section cooling and last passage of finish rolling, separates out as relaxation and controls phase transformation control, ultrafast cooling device etc.Cooldown rate is greater than 20 DEG C/s.
(5) after section cooling, coiled sheet is coiled into through coiling machine.Coiling temperature scope, not higher than 400 DEG C, is not less than 300 DEG C.
The foundation of the TMCP process system of X70 pipe line steel of the present invention is:
X70 pipe line steel of the present invention adopts the mode of ' controlled rolling+accelerating cooling ' to produce, and it obtains best grain refining effect by the distortion accumulation of austenite recrystallization district Deformation recrystallization, austenite Unhydrated cement and the accelerating cooling after rolling.Control is carried out and crystal grain thinning to microscopic structure, multi-pass rolling is carried out in the lower temperature region of austenite recrystallization district and austenite Unhydrated cement, carrying out under higher cooling velocity (>=20 DEG C/S), make deformed austenite change into fine uniform based on acicular ferrite, containing a small amount of granular bainite composition heterogeneous structure.
The present invention has following technique effect:
(1) X70 pipe line steel of the present invention has more stable intensity and excellent low-temperature impact toughness.
(2) crystallite dimension of X70 pipe line steel of the present invention is tiny, grain size 12 ~ 13 grades.
(3) microscopic structure of X70 pipe line steel of the present invention is acicular ferrite, containing a small amount of granular bainite, there is quasi-polygonal ferrite and the martensite/austenite of minute quantity.
(4) the yield strength representative value of X70 coiled sheet of the present invention is 530MPa, tensile strength representative value 650MPa, and-20 DEG C of summers are 400J(10 × 10 × 55mm than V-type ballistic work representative value).After tubulation, the yield strength representative value of economical high tenacity X70 pipe is 510MPa, tensile strength representative value 645MPa.-20 DEG C of Charpy impact sections of shear (SA%) 100% ,-15 DEG C of DWTT of coiled sheet and steel pipe are 100%.
(5) show through batch production practice, the composition designed by this patent and technique can reduce costs and steady production X70 pipe line steel coiled sheet effectively, solve the problem that Bauschinger effect is obvious and alloy designs cost is higher simultaneously.
Accompanying drawing explanation
Below in conjunction with accompanying drawing to the detailed description of the invention:
1/4 thickness place microscopic structure rolled up by Fig. 1: 11.1mmh slab.
1/4 thickness place microscopic structure rolled up by Fig. 2: 17.5mm slab.
Detailed description of the invention
According to the chemical composition ranges of pipe line steel of the present invention, through 300 tons of converter smeltings, through ladle argon-blown, the refining of LF stove, RH application of vacuum and continuous casting, again after heating, enter two frame R1 and R2 roughing, carry out thermomechanical controlled rolling through 7 frame 2250mm Continuous mill train production lines again, roll rear employing pipe line steel steel high strength process for cooling, hot rolled thickness specification 11.1mm, 17.5mm.
The chemical composition of X70 pipe line steel of the present invention is in table 1, and TMCP thermomechanical controlled rolling process system is in table 2, and performance is in table 3 ~ table 5.
Being mingled with of X70 pipe line steel of the present invention, microscopic structure and grain size are in table 6 ~ table 7.
The chemical composition of table 1 X70 pipe line steel of the present invention, wt%
| Retort number | Rolling lot number | C | Si | Mn | P | S |
| 12304041 | H120868000 | 0.075 | 0.12 | 1.12 | 0.014 | 0.0013 |
| 12303829 | H120810760 | 0.051 | 0.35 | 1.61 | 0.013 | 0.0005 |
| 12303322 | H120852020 | 0.063 | 0.20 | 1.38 | 0.010 | 0.0007 |
| 12303972 | H120851580 | 0.067 | 0.25 | 1.55 | 0.010 | 0.0007 |
The chemical composition of continued 1 X70 pipe line steel of the present invention, wt%
| Retort number | Rolling lot number | Nb | Ti | N | Als | Cr |
| 12304041 | H120868000 | 0.067 | 0.0202 | 0.0050 | 0.022 | 0.35 |
| 12303829 | H120810760 | 0.079 | 0.0248 | 0.0044 | 0.024 | 0.38 |
| 12303322 | H120852020 | 0.051 | 0.0114 | 0.0047 | 0.024 | 0.31 |
| 12303972 | H120851580 | 0.061 | 0.0137 | 0.0047 | 0.023 | 0.33 |
The TMCP process system of table 2 X70 pipe line steel of the present invention
The service check result of table 3 X70 pipe line steel of the present invention
The impact property (7.5 × 10 × 55mm) (with rolling to becoming 30o direction) of table 4 X70 volume of the present invention
The impact property (10 × 10 × 55mm) (with rolling to becoming 30o direction) of table 5 X70 volume of the present invention
The field trash type (rank) of table 6 X70 of the present invention
The microscopic structure of table 7 X70 of the present invention and grain size
| Lot number | Microscopic structure | Prior austenite grain size (level) |
| H120868000 | Acicular ferrite+granular bainite | 13.0 |
| H120810760 | Acicular ferrite+granular bainite | 12.5 |
| H120852020 | Acicular ferrite+granular bainite | 12.0 |
| H120851580 | Acicular ferrite+granular bainite | 12.0 |
Claims (1)
1. one kind contains Cr economical X 70 pipeline steel hot-rolling coiled sheet, it is characterized in that, the chemical component weight percentage (%) of described coiled sheet is: C 0.05-0.075%, Si 0.10%-0.35%, Mn 1.00-1.65%, Nb 0.050-0.080%, Ti 0.010-0.025%, Cr 0.30-0.4%, surplus is iron and inevitable impurity; The microscopic structure of described coiled sheet is the acicular ferrite based on fine uniform, adds the heterogeneous structure of a small amount of granular bainite composition, grain size 12 ~ 13 grades; The cooling controlling and rolling controlling process of described coiled sheet is:
(1) heating-up temperature 1150 ~ 1210 DEG C, soaking time is no less than 120 minutes,
(2) roughing rolling pass is distributed: use 8 ~ 10 passage roughing, and every time deflection requires between 10 ~ 20%, the deflection 17-20% of last 3 passages of roughing,
(3) finish rolling rolling pass is distributed: finish rolling first passage rolling temperature is not higher than 1050 DEG C, and last pass deformation of finish rolling is less than 8%, and last two passage cumulative deformations are less than 16%, finish rolling finishing temperature 770 DEG C-850 DEG C,
(4) section cooling is implemented immediately after finish rolling, cooldown rate 20-25 DEG C/s,
(5) after section cooling, coiled sheet is coiled into through coiling machine, coiling temperature 300-400 DEG C.
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| CN201310001803.4A CN103042039B (en) | 2013-01-05 | 2013-01-05 | Controlled rolling and cooling process for Cr-containing economic X70 pipeline hot-rolled steel coil plate |
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| CN201310001803.4A CN103042039B (en) | 2013-01-05 | 2013-01-05 | Controlled rolling and cooling process for Cr-containing economic X70 pipeline hot-rolled steel coil plate |
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| CN108193141B (en) * | 2017-12-29 | 2020-02-07 | 东北大学 | V-N-Cr microalloyed Q550-grade hot rolled strip steel and preparation method thereof |
| CN108588557B (en) * | 2018-04-26 | 2019-12-03 | 东北大学 | A kind of micro-alloyed hot-rolled strip of low-carbon V-N-Nb and preparation method thereof |
| CN111270156A (en) * | 2020-03-18 | 2020-06-12 | 本钢板材股份有限公司 | Production process of hot-rolled X70 pipeline steel with thickness specification of 20.0-25.4 mm |
| CN113637922A (en) * | 2020-04-27 | 2021-11-12 | 宝山钢铁股份有限公司 | Economical low-yield-ratio high-strength steel and manufacturing method thereof |
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| CN101525722B (en) * | 2009-04-22 | 2011-04-20 | 首钢总公司 | Excellent-toughness X70 hot-rolled sheet steel and manufacturing method therefor |
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