CN102732696B - Normalization heat treatment method of heavy-gauge low-alloy steel plates - Google Patents
Normalization heat treatment method of heavy-gauge low-alloy steel plates Download PDFInfo
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Abstract
The invention provides a normalization heat treatment method of heavy-gauge low-alloy steel plates. The method concretely comprises the steps of heating, heat insulating and cooling. The steel plates prepared through the method of the invention comprise the following components: 0.18% or less of C, 0.50% or less of Si, 1.60% or less of Mn, 0.020% or less of P, 0.010% or less of S, 0.06% or less of Nb, 0.02-0.06% of Al, 0.03% or less of Ti, 0.08% or less of V, and the balance Fe and inevitable impurities. Different heat insulation time and cooling technologies are adopted according to different thicknesses of the steel plates, the heat insulation period is 1.8min/mm and a rolling transmission and collector spray water laminar flow mode is adopted to cool when the thicknesses of the steel plates are equal to or less than 100mm, and the heat insulation period is 2.0-2.2min/mm and a water tank cooling mode is adopted to cool when the thicknesses of the steel plates are greater than 100mm. The normalizing heat treatment technology of the invention allows the cooling intensity and the cooling speed of cores of the steel plates to be improved, the nucleation rate of the steel plates to be improved, tissues in the centers of the steel plates to be refined, the quality of the steel plates to be guaranteed and bad tissues and performances caused by uneven heavy-gauge steel plate cooling to be effectively solved, and is especially suitable for heat treatment technologies of thick steel plates.
Description
Technical field
The invention belongs to the technical field of heat treatment of steel plate, be specifically related to a kind of normalizing heat treatment method of heavy thickness Low Alloy Steel Plate.
Background technology
Normalizing thermal treatment steel is heated to the suitable temperature of Ac3 or more than Acm, and after held for some time, cooling obtains the thermal treatment process of ferritic-pearlitic tissue, and normalizing thermal treatment can crystal grain thinning, elimination internal stress, elimination Widmannstatten structure and banded structure.Deliver goods with as-normalized condition in most of low-alloy steel capital, this kind of heat treatment mode is often applied in the actual production of this steel grade, but the normalizing heat treatment mode of routine can only play good effect to the steel plate of Thin Specs, for heavy thickness steel plate, after the normalizing thermal treatment of routine, the improvement effect of grain fineness number, internal stress and adverse tissue is not clearly, and the object performance of steel plate is also greatly affected, and especially the performance of steel plate center is difficult to meet the demands.
Summary of the invention
For the problems referred to above, the object of the present invention is to provide a kind of normalizing heat treatment method of heavy thickness Low Alloy Steel Plate, by the mode of water-cooled accelerating cooling after normalizing, well solve the problems referred to above, be particularly suitable for the normalizing of Plate Steel.
The normalizing heat treatment method of heavy thickness Low Alloy Steel Plate of the present invention, its step is as follows:
(1) heat: normalizing Heating temperature is 890 ~ 920 DEG C;
(2) be incubated: during steel plate thickness≤100mm, at normalizing furnace soaking time: 1.8min/mm;
During steel plate thickness > 100mm, machine stove soaking time: 2.0 ~ 2.2min/mm outside;
(3) water-cooling process: steel plate enters water cooling after going out process furnace in time, the timed interval from coming out of the stove water-cooled is no more than 0.5min; As steel plate thickness≤100mm, adopt the dynamic transmission of roller, the cooling of collector water spray layer flow mode, open 0 ~ 21 group of water, roller speed control is built in 4m/min ~ 40m/min; As steel plate thickness > 100mm, adopt tank cooling, control steel plate at water cooling time 1 ~ 8min, control tank quantity of exchanged water per hour about 100 tons and control water temperature≤40 DEG C; Finally guarantee that steel plate cooling rate, red temperature and cooling intensity are suitable.
Collector section cooling described in step (3), control upper and lower water than being 1:2 ~ 3, tank cooling controls steel plate and stand up mode in water, upright in the sink or tilt 45 ° or lie low in the sink, control that steel plate is upper and lower changes water mode, following table adopts agitator to stir, and in minimizing, following table speed of cooling is poor.
Steel plate cooling rate≤9 described in step (3) DEG C/s, red temperature controls at 560 DEG C ~ 720 DEG C, guarantee that steel plate core reaches the cooling rate of 5 DEG C/more than s, upper layer bayesian scale of construction thickness is no more than 3mm simultaneously, and be superfine bainite, grain fineness number reaches more than 11 grades, and namely tissue obtains a small amount of superfine bainite in main body ferrite+perlite+surface.Both ensured that steel plate core was fine grained steel, and suitably improved the intensity in whole thickness of slab direction simultaneously, ensure that the homogeneity of steel plate tissue, performance.
The steel plate component concentration that the present invention's normalizing heat treatment mode is produced is: C≤0.18%, Si≤0.50%, Mn≤1.60%, P≤0.020%, S≤0.010%, Nb≤0.06%, Al:0.02 ~ 0.06%, Ti≤0.03%, V≤0.08%, surplus is Fe and inevitable impurity, and what obtain is organized as ferrite+perlite+a small amount of superfine bainite.
Normalizing heat treatment mode of the present invention is equipped with suitable water-cooling process after normalizing, water-cooling process is determined according to the thickness of steel plate, intensity, quality grade and alloying element content, after normalizing, water-cooled adds the condensate depression of steel plate, especially improve the cooling intensity of steel plate core, speed of cooling, improve the nucleation rate of steel plate, the tissue of refinement steel plate center, ensure that the quality in kind of steel plate, efficiently solves tissue, performance difference that heavy thickness steel plate causes because of inhomogeneous cooling.
Normalizing heat treatment method of the present invention can ensure yield strength and the tensile strength of steel plate in the alloying element situation adding seldom amount, improves steel plate core toughness, makes it have higher low-temperature impact work, greatly reduce production cost.Controlled by normalizing process for cooling, alloy (Nb, V, Ti) can be saved, according to steel plate thickness and quality grade, save alloy expense 20 ~ 80 yuan/t.
Embodiment
Embodiment 1
The normalizing heat treatment method of the heavy thickness low-alloy Q345E steel plate of the present embodiment, the thickness of this steel plate is 80mm, and steel plate chemical composition is as follows: C:0.16%, Si:0.30%, Mn:1.55%, P:0.015%, S:0.005%, Nb:0.020%, Al:0.045%, Ti:0.002%, V:0.006%, surplus is Fe and inevitable impurity.
Concrete steps are:
(1) heat: normalizing Heating temperature is 900 DEG C;
(2) be incubated: soaking time is 1.8min/mm;
(3) water-cooling process: steel plate enters water cooling after going out process furnace in time, the timed interval from coming out of the stove water-cooled is 0.5min; Adopt the dynamic transmission of roller, the cooling of collector water spray layer flow mode, open 4 ~ 21 groups of water, upper and lower water ratio is 1: 2.4, and control roller speed is 24m/min, and guarantee that steel plate cooling rate is 9 DEG C/s, red temperature is 620 DEG C.
The mechanical property of the present embodiment steel plate: yield strength: 410MPa, tensile strength: 550MPa, unit elongation: 28% ,-40 DEG C of ballistic works: more than 200 joules.
Embodiment 2
The normalizing heat treatment mode of the heavy thickness low-alloy S355J2+N steel plate of the present embodiment, the thickness of this steel plate is 180mm, and steel plate chemical composition is as follows: C:0.18%, Si:0.35%, Mn:1.50%, P:0.015%, S:0.010%, Nb:0.020%, Al:0.045%, Ti:0.002%, V:0.006%, surplus is Fe and inevitable impurity.
Concrete steps are:
(1) heat: normalizing Heating temperature is 920 DEG C;
(2) be incubated: soaking time is 2.0min/mm;
(3) water-cooling process: steel plate enters water cooling after going out process furnace in time, the timed interval from coming out of the stove water-cooled is 0.3min; Employing tank cools, and controlling steel is 1.5min in the water cooling time, by controlling quantity of exchanged water per hour 100 tons and water temperature 40 DEG C, controlling steel plate and standing up mode in water, adopting and lie low in the sink; Control that steel plate is upper and lower changes water mode, following table adopts agitator to stir, and in minimizing, following table speed of cooling is poor, and guarantee that steel plate cooling rate is 8 DEG C/s, red temperature is 700 DEG C.
The mechanical property of the present embodiment steel plate: yield strength: 390MPa, tensile strength: 540MPa, unit elongation: 31% ,-20 DEG C of ballistic works: more than 120 joules.
Claims (1)
1. a normalizing heat treatment method for heavy thickness Low Alloy Steel Plate, is characterized in that, described concrete steps are as follows:
(1) heat: normalizing Heating temperature is 900 ~ 920 DEG C;
(2) be incubated: during steel plate thickness≤100mm, soaking time 1.8min/mm;
During steel plate thickness > 100mm, soaking time: 2.0 ~ 2.2min/mm;
(3) water-cooling process: steel plate enters water cooling after going out process furnace in time, the timed interval from coming out of the stove water-cooled is no more than 0.5min; As steel plate thickness≤100mm, adopt the dynamic transmission of roller, the cooling of collector water spray layer flow mode, open 4 ~ 21 groups of water, roller speed control is built in 4m/min ~ 40m/min; As steel plate thickness > 100mm, adopt tank cooling, control steel plate at water cooling time 1 ~ 8min, control quantity of exchanged water per hour about 100 tons and water temperature≤40 DEG C; Final steel plate cooling rate≤9 DEG C/s, red temperature is 560 ~ 720 DEG C;
Collector water spray section cooling described in step (3), controls upper and lower water than being 1:2 ~ 3; Tank cooling controls steel plate and stand up mode in water, and uprightly in the sink or tilt 45 ° or lie low in the sink, control that steel plate is upper and lower changes water mode, following table adopts agitator to stir;
The component concentration of the steel plate produced is: C≤0.18%, Si≤0.50%, Mn≤1.60%, P≤0.020%, S≤0.010%, Nb≤0.06%, Al:0.02 ~ 0.06%, Ti≤0.03%, V≤0.08%, and surplus is Fe and inevitable impurity.
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| CN104498674B (en) * | 2014-12-15 | 2017-01-04 | 内蒙古包钢钢联股份有限公司 | Steel plate cooling means |
| CN107267861A (en) * | 2017-05-31 | 2017-10-20 | 舞阳钢铁有限责任公司 | Continuous casting billet produces normalized high-strength S460NL steel plates and its production method |
| CN109929972A (en) * | 2019-04-02 | 2019-06-25 | 浙江明贺钢管有限公司 | A kind of steel pipe non-oxidation normalizing process and device |
| CN110551879B (en) * | 2019-09-19 | 2021-06-22 | 舞阳钢铁有限责任公司 | Production method of low-strength-level Cr-Mo steel plate |
| CN114231705A (en) * | 2021-12-22 | 2022-03-25 | 舞阳钢铁有限责任公司 | Normalizing heat treatment method for large-thickness P460NH steel |
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