CN109554529A - A kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique - Google Patents
A kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique Download PDFInfo
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- CN109554529A CN109554529A CN201811548376.0A CN201811548376A CN109554529A CN 109554529 A CN109554529 A CN 109554529A CN 201811548376 A CN201811548376 A CN 201811548376A CN 109554529 A CN109554529 A CN 109554529A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
- C21D3/02—Extraction of non-metals
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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Abstract
A kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique of the invention, step are as follows: hot-strip is rapidly heated with 80~150 DEG C/s to 400~550 DEG C, 30~600s of Isothermal Reduction, reduzate is Multiple level sponge iron, after cooling during rolling, 700~1100 DEG C are warming up to 80~150 DEG C/s, 30~600s of Isothermal Reduction, iron particle is mutually bonded in Multiple level sponge iron, crystal grain is grown up, pass through mass transfer, reduzate intermediate gap, stomata and crystal boundary gradually decrease, total volume is shunk, being formed has microstructural dense multicrystalline body pure iron layer, complete scale reduction, restoring method of the invention is remarkably improved reduction efficiency of the hot rolling strip steel scale in continuous annealing furnace, in the shorter recovery time can get largely restore it is pure Iron avoids influence of the iron scale residual to subsequent plating layer mouldability and adhesiveness, to ensure that the commercial introduction for exempting from pickling reduced anneal hot galvanizing prototyping technique.
Description
Technical field:
The invention belongs to metallurgical technology fields, and in particular to a kind of hot-strip iron oxide based on reduction pretreatment technique
Skin restoring method.
Background technique:
Currently, the method for major iron and steel enterprise removal iron scale is generally that hydrochloric acid or sulfuric acid is used to carry out acid both at home and abroad
It washes, pickling technology can provide ideal metal surface, however be easy to cause air pollution for a long time with intensive use acid solution
And underground water pollution, ecological environment is caused great harm.In view of environmental requirement, domestic and international enterprise and scientific research institutions are to exempting from acid
It washes technique of scale removal and expands extensive research, propose gas (H2, CO) reduction replace pickling remove hot-strip product surface oxygen
Change the new method of iron sheet, i.e. the pickling of exempting from of hot-strip iron scale restores technique of scale removal.The gas reduction de-scaling of hot-strip
Technology is derived from pyrometallurgical smelting iron ore field earliest, and the technique of metal is extracted from oxide.Main processes are specific
Under reduction temperature, fuel gas (H2Or CO) reducing agent is made, oxide is restored to obtain crude metal or alloy.Hot-strip oxidation
The gas reduction process of iron sheet is similar to gas reduction iron ore, in continuous annealing furnace, is passed through reducing atmosphere, by hot-rolled strip
Steel surface scale reduction substitutes pickling at pure Fe.The technique have the characteristics that cleaning, it is efficient and high-quality, once propose just by
The extensive concern of steel industry is arrived.
Hot rolling strip steel scale is by H2Or the process of CO reduction thermodynamically carries out step by step.Be first to be formed compared with
Low oxide eventually forms simple substance Fe.Fe is as transiting group metal elements, and in high-temperature oxydation, meeting goes out there are three types of oxide
Show, respectively FeO, Fe3O4And Fe2O3.Under the action of O, the sequence that oxide is formed follows the principle changed step by step.Simultaneously
Due to 570 DEG C of critical-temperatures as FeO disproportionated reaction, different transformation sequences is had higher or lower than the critical-temperature, because
The reduction of this iron scale also has property step by step.Under condition of different temperatures, H2For example following side of the reaction process of reduction-oxidation iron sheet
Shown in formula, CO reduction process and H2It is identical.
When reaction temperature is at 570 DEG C or more:
3Fe2O3+H2=2Fe3O4+H2O(g)
Fe3O4+H2=3FeO+H2O(g)
FeO+H2=Fe+H2O(g)
When reaction temperature is at 570 DEG C or less:
3Fe2O3+H2=2Fe3O4+H2O(g)
However, being utilized " the exempting from pickling " of gas reduction removal iron scale in production practices and laboratory theoretical research
Technology also faces following problem:
(1) selection of reducing agent, CO are toxic gases, need to increase safety cost in use；Reaction product CO2
It will cause environmental pollution, need to build tail gas filtering and recyclable device；C in reducing agent can enter matrix surface in reaction
Cementite is formed, the final mechanical property of material is influenced.Compared with CO, H2Diffusion and transmittability it is stronger, reaction efficiency compared with
Fastly.Reduzate is vapor no pollution to the environment, it is possible to reduce the investment of tail gas treatment device, green energy resource H2It is imitated in reduction
Advantage in terms of rate becomes preferred reducing agent in gas reduction descaling process, but due to H2Belong to explosion hazard gases, is using
Safety cost is needed to put into the process.
(2) reductant concentration, to improve safety coefficient, H in the mixed gas of the interior use of annealing furnace at present2Concentration is lower
(≤8%), so that reduction reaction efficiency is slow, all reduction required time is too long for iron scale, is unsuitable for actual production line and answers
With.
(3) reduction temperature, the setting of reductive annealed oven temperature schedule is unreasonable, and annealing furnace is added using unistage type at present
Heat, furnace chamber temperature are generally lower than 750 DEG C, and reducing agent diffusion rate is slow, reduction reaction low efficiency.
(4) " gas-solid " phase reaction and reduzate, reducing agent are reacted with the iron scale on steel surface layer, the reduction on surface layer
Product is metallic iron, forming core can grow up to form fine and close pure iron layer at high temperature, once fine and close pure iron layer is formed too early, can prolong
Delay H to the diffusion rate inside iron scale, reduces reduction reaction rate.
Summary of the invention:
The purpose of the present invention is exempt from Surfaces of Hot Rolled Strip oxygen in pickling reduced anneal Hot Galvanizing Technology in the prior art
Change iron sheet reduction efficiency in continuous annealing furnace is low, residual oxidization iron sheet amount needs asking for galvanized sheet processability after excessively influencing
Topic, provides a kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique, utilizes polycrystalline circle in iron scale
Eutectoid structure is in H2In reduction characteristic, added before high temperature reduction section with the reduction pretreatment section that quickly heats, and prepare
Great surface quality, good processability exempt from pickling heat zinc coating plate out, provide new approaches for industrial application, so that hot rolling
The iron scale of belt steel surface can be reduced into fine and close pure iron layer with faster rate, reduce continuous annealing furnace investment at
This while, improves the adhesiveness and mouldability of heat zinc coating plate.
To achieve the above object, the invention adopts the following technical scheme:
A kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique, comprising the following steps:
Step 1, it preheats:
Hot-strip is warming up to 200~300 DEG C, completes preheating；
Step 2, reduction pretreatment:
(1) by strip after preheating with the heating rate of 80~150 DEG C/s, 400~550 DEG C quickly heating: are heated to；
(2) reduction pretreatment: strip after heating is subjected to Isothermal Reduction, generates strip after prereduction；Wherein, it is described also
Former temperature is 400~550 DEG C, and the recovery time is 30~600s, reducing atmosphere H2And N2Mixed atmosphere, wherein H2Volume
Concentration is 5~50%；
Step 3, cooling during rolling:
By strip after prereduction with the cooling rate of 10~20 DEG C/s, 300~500 DEG C are cooled to, strip after being cooled down；
Step 4, high temperature reduction:
(1) quickly heating: strip is warming up to 700~1100 DEG C with the heating rate of 80~150 DEG C/s after cooling；
(2) high temperature reduction: strip carries out Isothermal Reduction after heating, completes scale reduction, and be cooled to room temperature；Its
In, the reduction temperature is 700~1100 DEG C, and the recovery time is 30~600s, reducing atmosphere H2And N2Mixed atmosphere,
Wherein H2Volumetric concentration be 5~100%.
In the step 1, the ingredient of hot-strip contains C:0.03~0.10% by weight percentage, and Si:0.04~
0.60%, Mn:0.15~2.5%, S :≤0.015%, P :≤0.019%, Cr:0.2~1.0%, Als:0.015~
0.045%, Ti :≤0.08%, Nb :≤0.08%, surplus inevitable impurity when being Fe and smelting.
In the step 1, hot-strip with a thickness of 1.3~3.0mm, the start rolling temperature 950~1050 of hot-strip
DEG C, 800~900 DEG C of finishing temperature, coiling temperature is 350~500 DEG C, iron scale with a thickness of 4~8 μm, cooling rate is
0.01~0.05 DEG C/s, sheet eutectoid structure Fe in iron scale3O4The ratio of/α-Fe is 60~100%.
In the step 1, preheating method is heated using radiant tube.
In the step 1, heating rate is 30~60 DEG C/s.
In the step 2 (1), by controlling heating ramp rate, original eutectoid structure in iron scale is prevented
(Fe3O4/ α-Fe) reverse transformation occurs, so that the ratio of sheet eutectoid structure is retained in 60~100%.
In the step 2 (2), strip institutional framework is Multiple level sponge after the prereduction obtained after reduction pretreatment
Iron.
In the step 4 (1), belt steel surface reduzate is still Multiple level sponge iron after keeping cooling.
Iron in the step 4 (2), after Isothermal Reduction, in the reduzate Multiple level sponge iron of belt steel surface
Grain can be mutually bonded, and crystal grain is grown up, and is gradually decreased by gap, stomata and the crystal boundary in mass transfer reduzate, overall
Product is shunk, and is ultimately formed with microstructural dense multicrystalline body pure iron layer.
In the step 4 (2), after scale reduction, strip is used to prepare galvanized sheet, detailed process are as follows:
(1) strip after scale reduction is cooled to 450~480 DEG C with the rate of 10~30 DEG C/s, be then immersed in
Hot galvanizing is carried out into zinc liquid；Wherein, the zinc liquid temperature is 450~480 DEG C, includes that component and weight percent contain in zinc liquid
Amount is Al0.4~6.0%, and Sb≤0.07%, surplus is pure Zn；
(2) by the way of strip is combined using the forced cooling and natural cooling of routine after zinc-plated, to the strip after zinc-plated
It is cooled down, galvanized sheet is made.
In the present invention, in order to improve reduction efficiency, carried out between reduction pretreatment and high temperature reduction operation intermediate cold
But, in reduction pretreatment and high temperature reduction section, the method for control burning velocity and temperature is respectively adopted to control reduction process,
Cooling during rolling stage, belt steel temperature decline 50~100 DEG C, since substrate and reduzate contract on cooling rate difference, can restore
Surface forms a large amount of micro-crack, can be the inside diffusion of reducing gas and providing to external diffusion for reduzate vapor
Diffusion admittance.
In the step 2 and step 4, during reduction pretreatment and high temperature reduction, control dew point value control is -70
DEG C hereinafter, concrete operations are as follows: measure the water vapour content in furnace chamber using gas dew point analyzer, controlled using pyrographite
Water vapour content (C+H in furnace processed2O=CO+H2), make dew point value control at -70 DEG C hereinafter, CO content is kept in furnace atmosphere
5~30%.
A kind of efficient restoring method of hot rolling strip steel scale based on reduction pretreatment technique of the invention, it is used
The thickness specification of hot-strip is 1.3~3.0mm, and the steel product of the thickness specification is all finally the production of roll bending form at present.
Blocked up for Surfaces of Hot Rolled Strip iron scale used by preventing, when production, is all made of the technique of " high temperature rolls fastly ", by iron oxide
The thickness control of skin is at 4~8 μm.The temperature range of belt steel product when take-up is 400~700 DEG C, since strip is coiled cold
But, so cooling rate is slower, according to Fe-O phasor it is found that the FeO in iron scale can be undergone phase transition at 570 DEG C or less,
It is changed into pro-eutectoid Fe3O4Or eutectoid structure (Fe3O4/α-Fe).Therefore the cooling technique setting of hot-strip will will affect final
Scale structure, since performance differs greatly between different tissues structure, thus scale structure control, can to its even
Reduction efficiency in continuous annealing furnace has very big influence.Therefore, this patent is by sheet eutectoid structure Fe in iron scale3O4/
The ratio of α-Fe is controlled 60~100%.
Method of the invention is different from the above-mentioned method using segmented reduction-oxidation iron sheet.In order to inhibit iron scale
In inverse eutectoid phase transformation, prevent Fe3O4+ Fe → FeO occurs, and the present invention is devised with the reduction pretreatment section quickly heated, should
The temperature in stage is 350~550 DEG C, while by the way of quickly heating, and heating rate optimum is 80~150 DEG C/s.
The purpose for using this reduction temperature is controlled the temperature of reduction pretreatment in phase transformation critical-temperature (570 DEG C) hereinafter, to guarantee
Eutectoid structure (Fe3O4/ α-Fe) stability, H can be diffused by crystal boundary when reduction, and eutectoid structure is more grain boundary structures
More diffusion admittances can be provided for its diffusion, while also increase the contact area of H and oxide, so that iron scale can
To be rapidly reduced into porous iron.It meanwhile using the purpose of this heating rate being to reduce in temperature-rise period iron inside iron scale
The diffusion rate of oxonium ion prevents that solid-state phase changes occur inside iron scale in temperature-rise period, is especially to ensure that strip exists
Eutectoid structure content when reduction pretreatment section in iron scale does not reduce.
According to the binary alloy phase diagram of Fe-Zn it is found that in the zinc liquid without Al when hot galvanizing, it can be formed inside coating
The Fe-Zn phase such as η, ζ, σ and Γ, since metallic compound is hard and crisp compared with pure zinc, this is just degrading the performance of coating, to coating
Forming property is unfavorable.Therefore, be improve coating adhesiveness and processing performance, in zinc liquid add mass fraction be 0.15~
0.20% Al can take the lead in forming Fe on surface in this way when matrix enters zinc pot2Al5Layer plays inhibition to Fe-Zn reaction and makees
With the generation of inhibition Fe-Zn brittlement phase.Hot rolling strip steel scale based on reduction pretreatment technique of the invention efficiently restores
Method is a kind of using H2The method that reduction replaces pickling removal iron scale, iron scale table after continuous annealing furnace reduction
Face will form fine and close pure iron layer, and surface roughness becomes larger at this time, will affect the distribution of Al and Fe in coating2Al5The shape of inhibition layer
At, and then destroy coating microstructure uniformity and adhesiveness.Therefore, the mass percent of Al in zinc liquid is designed as 0.4 by the present invention
~6.0%.
Beneficial effects of the present invention:
(1) scale reduction reaction is greatly improved by the characteristic of iron scale itself solid-state phase changes in the present invention
Efficiency, so that iron scale can be reduced into pure iron within a short period of time；
(2) present invention absorbs reduzate vapor using pyrographite, and obtained reaction product CO also will continue to
Play the role of reducing agent in furnace, that is, efficiently controlled the dew point in furnace, also reduces hydrogen usage amount.
Detailed description of the invention:
Fig. 1 is the surface SEM shape appearance figure of strip after the prereduction obtained after reduction pretreatment in the embodiment of the present invention 1；
Fig. 2 is the surface SEM shape appearance figure of strip after being cooled down after the cooling during rolling in the embodiment of the present invention 1；
Fig. 3 is the hot rolling strip steel scale restoring method technique based on reduction pretreatment technique of the embodiment of the present invention 1
Figure, wherein 1.-preheating, 2.-quickly heating, 3.-reduction pretreatment, 4.-cooling during rolling, 5. secondary rapid heating, 6. high temperature is also
Original, 7.-cooling, T1It is 200~300 DEG C, T2It is 400~550 DEG C, T3It is 300~500 DEG C, T4It is 700~1100 DEG C；
Fig. 4 is hot rolling strip steel scale section SEM shape appearance figure in the embodiment of the present invention 1；
Fig. 5 is to obtain the surface SEM shape appearance figure of reduzate after restoring in the embodiment of the present invention 1；
Fig. 6 is to obtain the section SEM shape appearance figure of reduzate after restoring in the embodiment of the present invention 1；
Fig. 7 is the heat zinc coating plate processability test that after completing scale reduction in the embodiment of the present invention 1 prepared by strip
Flexure plane photo；
Fig. 8 is hot rolling strip steel scale section SEM shape appearance figure in the embodiment of the present invention 2；
Fig. 9 is to obtain the surface SEM shape appearance figure of reduzate after restoring in the embodiment of the present invention 2；
Figure 10 is to obtain the section SEM shape appearance figure of reduzate after restoring in the embodiment of the present invention 2；
Figure 11 is the heat zinc coating plate processability test that after completing scale reduction in the embodiment of the present invention 2 prepared by strip
Flexure plane photo；
Figure 12 is to obtain the surface SEM shape appearance figure of reduzate after restoring in the embodiment of the present invention 3；
Figure 13 is to obtain the section SEM shape appearance figure of reduzate after restoring in the embodiment of the present invention 3；
Figure 14 is the heat zinc coating plate processability test that after completing scale reduction in the embodiment of the present invention 3 prepared by strip
Flexure plane photo；
Figure 15 is the heat zinc coating plate processability test that after completing scale reduction in the embodiment of the present invention 4 prepared by strip
Flexure plane photo；Wherein: A- steel matrix, B- eutectoid structure, C- iron scale, D- reduzate.
Specific embodiment:
Below with reference to embodiment, the present invention is described in further detail.
The ingredient of hot-strip contains C:0.03%~0.10%, Si:0.04% by weight percentage in the embodiment of the present invention
~0.60%, Mn:0.15%~2.5%, S :≤0.015%, P :≤0.019%, Cr:0.2%~1.0%, Als:0.015%
~0.045%, Ti :≤0.08%, Nb :≤0.08%, remaining is Fe and impurity inevitable when smelting.
Hot-strip with a thickness of 1.3~3.0mm, the start rolling temperature 950~1050 of hot-strip in the embodiment of the present invention
DEG C, 800~900 DEG C of finishing temperature, coiling temperature is 350~500 DEG C, iron scale with a thickness of 4~8 μm, cooling rate is
0.01~0.05 DEG C/s, sheet eutectoid structure Fe in iron scale3O4The ratio of/α-Fe is 60~100%.
Hot-strip passes sequentially through five stages in continuous annealing furnace in the embodiment of the present invention, respectively preheating section, fast
Reduction pretreatment section, cooling during rolling section and the high temperature reduction section and cooling section quickly heated of speed heating.
Hot-strip is in the quick heating ramp rate of reduction pretreatment section and high temperature reduction section in the embodiment of the present invention
80~150 DEG C/s.
It is measured in reduction pretreatment section and high temperature reduction section using gas dew point in continuous annealing furnace in the embodiment of the present invention
Instrument measures the water vapour content in furnace chamber, controls the water vapour content (C+H in continuous annealing furnace using pyrographite2O=
CO+H2), dew point value control is at -70 DEG C hereinafter, CO content is maintained at 5~30% in furnace atmosphere.
In the embodiment of the present invention in zinc liquid Al weight percent control 0.4~6.0%, Sb weight percent≤
0.07%, remaining is pure Zn.
Embodiment 1
A kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique, artwork is as shown in figure 3, packet
Include following steps:
(1) hot-strip is taken, 200 DEG C is warming up to 30 DEG C/s, is preheated, wherein the ingredient of hot-strip is by weight
Percentage contains C:0.03%, Si:0.04%, Mn:0.15%, S:0.015%, P:0.019%, Cr:0.2%, Als:
0.015%, remaining is Fe and impurity inevitable when smelting.Hot-strip with a thickness of 1.3mm, the section of iron scale is aobvious
Micromorphology as shown in figure 4, iron scale with a thickness of 6 μm, sheet eutectoid structure Fe in iron scale3O4The ratio of/α-Fe is
95%；
(2) the reduction pretreatment section quickly heated is rapidly heated with 150 DEG C/s to 550 DEG C, H2Volumetric concentration be
50%, Isothermal Reduction 30s, the surface SEM shape appearance figure of strip is as shown in Figure 1 after the prereduction obtained after reduction pretreatment；
(3) after strip reduction pretreatment, temperature is made to decline 100 DEG C with the cooling rate of 20 DEG C/s, strip after being cooled down
Surface SEM shape appearance figure it is as shown in Figure 2；
(4) the high temperature reduction section quickly heated is rapidly heated with 150 DEG C/s to 800 DEG C, H2Volumetric concentration be 20%,
Isothermal Reduction 180s completes scale reduction, and the surface of strip and section microstructure are respectively such as Fig. 5 and Fig. 6 institute after reduction
Show, reduzate is dense multicrystalline body pure iron layer and there are a large amount of micro-cracks on surface；In continuous annealing furnace, oxygen is completed
Strip after changing iron sheet reduction is cooled to 450 DEG C with 30 DEG C/s, is then immersed in zinc pot and carries out hot galvanizing, Al in zinc liquid ingredient
0.4%, remaining is pure Zn for weight percent control, heat zinc coating plate is made, using omnipotent mechanics machine to the heat produced
Galvanized sheet carries out 180 ° of cold bending experiments, and flexure plane is as shown in fig. 7, show the bright smooth zero defect of coating surface, heat zinc coating plate tool
There is preferable processability.
Embodiment 2
A kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique, comprising the following steps:
(1) hot-strip is taken, 300 DEG C is warming up to 60 DEG C/s, is preheated, in which: the ingredient of hot-strip is by weight
Percentage contains C:0.10%, Si:0.60%, Mn:1.0%, S:0.015%, P:0.019%, Cr:0.5%, Als:0.045%,
Ti:0.08%, remaining is Fe and impurity inevitable when smelting.Hot-strip with a thickness of 1.5mm, the section of iron scale
Microstructure as shown in figure 8, iron scale with a thickness of 6 μm, sheet eutectoid structure Fe in iron scale3O4The ratio of/α-Fe
It is 60%；
(2) the reduction pretreatment section quickly heated is rapidly heated with 100 DEG C/s to 500 DEG C, H2Volumetric concentration be
30%, Isothermal Reduction 60s；
(3) after strip reduction pretreatment, temperature is made to decline 80 DEG C with the cooling rate of 15 DEG C/s；
(4) the high temperature reduction section quickly heated is rapidly heated with 120 DEG C/s to 900 DEG C, H2Volumetric concentration be 5%, etc.
Temperature reduction 600s, completes scale reduction, the surface of strip and section microstructure are respectively such as Fig. 9 and Figure 10 institute after reduction
Show, reduzate is dense multicrystalline body pure iron layer and there are a large amount of micro-cracks on surface；In continuous annealing furnace, oxygen is completed
Strip after changing iron sheet reduction is cooled to 480 DEG C with 10 DEG C/s, is then immersed in zinc pot and carries out hot galvanizing, Al in zinc liquid ingredient
1.5%, remaining is pure Zn for weight percent control, heat zinc coating plate is made, using omnipotent mechanics machine to the heat produced
Galvanized sheet carries out 180 ° of cold bending experiments, and flexure plane is as shown in figure 11, shows the bright smooth zero defect of coating surface, heat zinc coating plate tool
There is preferable processability.
Embodiment 3
A kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique, comprising the following steps:
(1) hot-strip is taken, 300 DEG C is warming up to 45 DEG C/s, is preheated, in which: the ingredient of hot-strip is by weight
Percentage contains C:0.05%, Si:0.30%, Mn:0.5%, S:0.009%, P:0.010%, Cr:1.0%, Als:0.045%,
Ti:0.045%, Nb:0.08%, remaining is Fe and impurity inevitable when smelting.Hot-strip with a thickness of 2.0mm, oxygen
Change iron sheet with a thickness of 6.5 μm, sheet eutectoid structure Fe in iron scale3O4The ratio of/α-Fe is 70%；
(2) the reduction pretreatment section quickly heated is rapidly heated with 80 DEG C/s to 450 DEG C, H2Volumetric concentration be 5%,
Isothermal Reduction 600s；
(3) after strip reduction pretreatment, temperature is made to decline 50 DEG C with the cooling rate of 10 DEG C/s；
(4) the high temperature reduction section quickly heated is rapidly heated with 100 DEG C/s to 1100 DEG C, H2Volumetric concentration be
100%, Isothermal Reduction 30s complete scale reduction, and the surface topography of strip and section microstructure are respectively as schemed after reduction
Shown in 12 and Figure 13, reduzate is dense multicrystalline body pure iron layer and there are a large amount of micro-cracks on surface；In continuous annealing
In furnace, the strip after completing scale reduction is cooled to 460 DEG C with 20 DEG C/s, is then immersed in zinc pot and carries out hot galvanizing, zinc
3.0%, remaining is pure Zn for the weight percent control of Al in liquid ingredient, heat zinc coating plate is made, using omnipotent mechanics machine
180 ° of cold bending experiments are carried out to the heat zinc coating plate produced, flexure plane is as shown in figure 14, shows that coating surface is bright smooth intact
It falls into, heat zinc coating plate has preferable processability.
Embodiment 4
A kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique, comprising the following steps:
(1) hot-strip is taken, 300 DEG C is warming up to 60 DEG C/s, is preheated, wherein the ingredient of hot-strip is by weight
Percentage contains C:0.045%, Si:0.18%, Mn:0.2%, S:0.009%, P:0.010%, Cr:0.4%, Als:
0.045%, Ti:0.025%, Nb:0.045%, remaining is Fe and impurity inevitable when smelting.Hot-strip with a thickness of
3.0mm, iron scale with a thickness of 8 μm, sheet eutectoid structure Fe in iron scale3O4The ratio of/α-Fe is 60%；
(2) the reduction pretreatment section quickly heated is rapidly heated with 120 DEG C/s to 400 DEG C, H2Volumetric concentration be
20%, Isothermal Reduction 120s；
(3) after strip reduction pretreatment, temperature is made to decline 60 DEG C with the cooling rate of 10 DEG C/s；
(4) the high temperature reduction section quickly heated is rapidly heated with 80 DEG C/s to 700 DEG C, and the volumetric concentration of H2 is 75%, etc.
Temperature reduction 60s, completes scale reduction, and in continuous annealing furnace, the strip after completing scale reduction is cold with 20 DEG C/s
But it to 470 DEG C, is then immersed in zinc pot and carries out hot galvanizing, weight of the weight percent control of Al in 6%, Sb in zinc liquid ingredient
0.07%, remaining is pure Zn for percentage control, and heat zinc coating plate, the hot galvanizing using omnipotent mechanics machine to producing is made
Plate carries out 180 ° of cold bending experiments, and flexure plane is as shown in figure 15, shows the bright smooth zero defect of coating surface, heat zinc coating plate have compared with
Good processability.
Embodiment 5
A kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique, comprising the following steps:
(1) hot-strip is taken, 200 DEG C is warming up to 60 DEG C/s, is preheated, in which: the ingredient of hot-strip is by weight
Percentage contains C:0.03%, Si:0.04%, Mn:0.15%, S:0.007%, P:0.008%, Cr:0.2%, Als:
0.045%, remaining is Fe and impurity inevitable when smelting.Hot-strip with a thickness of 1.3mm, iron scale with a thickness of
4 μm, sheet eutectoid structure Fe in iron scale3O4The ratio of/α-Fe is 100%；
(2) the reduction pretreatment section quickly heated is rapidly heated with 150 DEG C/s to 500 DEG C, H2Volumetric concentration be
20%, Isothermal Reduction 100s；
(3) after strip reduction pretreatment, temperature is made to decline 50 DEG C with the cooling rate of 10 DEG C/s；
(4) the high temperature reduction section quickly heated is rapidly heated with 150 DEG C/s to 900 DEG C, H2Volumetric concentration be 50%,
Isothermal Reduction 120s completes scale reduction, and in continuous annealing furnace, the strip after completing scale reduction is with 30 DEG C/s
450 DEG C are cooled to, zinc pot is then immersed in and carries out hot galvanizing, weight of the weight percent control of Al in 5%, Sb in zinc liquid ingredient
Percentage control is measured 0.02%, remaining is pure Zn, and heat zinc coating plate, the hot dip using omnipotent mechanics machine to producing is made
Zine plate carries out 180 ° of cold bending experiments, shows that the bright smooth zero defect of coating surface, heat zinc coating plate have preferable processability.
Claims (7)
1. a kind of hot rolling strip steel scale restoring method based on reduction pretreatment technique, which is characterized in that including following step
It is rapid:
Step 1, it preheats:
Hot-strip is warming up to 200~300 DEG C, completes preheating；
Step 2, reduction pretreatment:
(1) by strip after preheating with the heating rate of 80~150 DEG C/s, 400~550 DEG C quickly heating: are heated to；
(2) reduction pretreatment: strip after heating is subjected to Isothermal Reduction, generates strip after prereduction；Wherein, the reduction temperature
Degree is 400~550 DEG C, and the recovery time is 30~600s, reducing atmosphere H2And N2Mixed atmosphere, wherein H2Volumetric concentration
It is 5~50%；
Step 3, cooling during rolling:
By strip after prereduction with the cooling rate of 10~20 DEG C/s, 300~500 DEG C are cooled to, strip after being cooled down；
Step 4, high temperature reduction:
(1) quickly heating: strip is warming up to 700~1100 DEG C with the heating rate of 80~150 DEG C/s after cooling；
(2) high temperature reduction: strip carries out Isothermal Reduction after heating, completes scale reduction, and cooled down；Wherein, described
Reduction temperature be 700~1100 DEG C, the recovery time be 30~600s, reducing atmosphere H2And N2Mixed atmosphere, wherein H2's
Volumetric concentration is 5~100%.
2. the hot rolling strip steel scale restoring method according to claim 1 based on reduction pretreatment technique, feature
It is, in the step 1, the ingredient of hot-strip contains C:0.03~0.10% by weight percentage, Si:0.04~
0.60%, Mn:0.15~2.5%, S :≤0.015%, P :≤0.019%, Cr:0.2~1.0%, Als:0.015~
0.045%, Ti :≤0.08%, Nb :≤0.08%, surplus inevitable impurity when being Fe and smelting.
3. the hot rolling strip steel scale restoring method according to claim 1 based on reduction pretreatment technique, feature
Be, in the step 1, hot-strip with a thickness of 1.3~3.0mm, 950~1050 DEG C of the start rolling temperature of hot-strip,
800~900 DEG C of finishing temperature, coiling temperature is 350~500 DEG C, iron scale with a thickness of 4~8 μm, cooling rate 0.01
~0.05 DEG C/s, sheet eutectoid structure Fe in iron scale3O4The ratio of/α-Fe is 60~100%.
4. the hot rolling strip steel scale restoring method according to claim 1 based on reduction pretreatment technique, feature
It is, in the step 1, heating rate is 30~60 DEG C/s.
5. the hot rolling strip steel scale restoring method according to claim 1 based on reduction pretreatment technique, feature
It is, in the step 2 (2), strip institutional framework is Multiple level sponge iron after the prereduction obtained after reduction pretreatment.
6. the hot rolling strip steel scale restoring method according to claim 1 based on reduction pretreatment technique, feature
It is, in the step 2, during reduction pretreatment and high temperature reduction, control dew point value control is at -70 DEG C hereinafter, tool
Gymnastics as: measure the water vapour content in furnace chamber using gas dew point analyzer, controlled in furnace using pyrographite
Water vapour content (C+H2O=CO+H2), make dew point value control at -70 DEG C hereinafter, in furnace atmosphere CO content be maintained at 5~
30%.
7. the hot rolling strip steel scale restoring method according to claim 1 based on reduction pretreatment technique, feature
It is, in the step 4 (2), after scale reduction, strip is used to prepare galvanized sheet, detailed process are as follows:
(1) strip after scale reduction is cooled to 450~480 DEG C with the rate of 10~30 DEG C/s, is then immersed in zinc
Hot galvanizing is carried out in liquid；Wherein, the zinc liquid temperature is 450~480 DEG C, and in zinc liquid include component and weight percentage is
Al0.4~6.0%, Sb≤0.07%, surplus are pure Zn；
(2) zinc-plated rear strip carries out the strip after zinc-plated in such a way that conventional forced cooling and natural cooling combine
It is cooling, galvanized sheet is made.
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| CN110195202A (en) * | 2019-05-08 | 2019-09-03 | 沈阳大学 | A method of hot rolled steel plate surface oxidation iron sheet crackle is repaired based on hydrogen reducing |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103726003A (en) * | 2013-12-20 | 2014-04-16 | 东北大学 | Hot rolled strip steel pickling-free hot galvanizing method based on scale reduction |
| CN105219929A (en) * | 2014-05-30 | 2016-01-06 | 宝山钢铁股份有限公司 | The sectional type method of reducing of hot-rolled sheet scale on surface |
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2018
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103726003A (en) * | 2013-12-20 | 2014-04-16 | 东北大学 | Hot rolled strip steel pickling-free hot galvanizing method based on scale reduction |
| CN105219929A (en) * | 2014-05-30 | 2016-01-06 | 宝山钢铁股份有限公司 | The sectional type method of reducing of hot-rolled sheet scale on surface |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110195202A (en) * | 2019-05-08 | 2019-09-03 | 沈阳大学 | A method of hot rolled steel plate surface oxidation iron sheet crackle is repaired based on hydrogen reducing |
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