CN102965486B - Technology for solving incomplete cleaning of acid washing on cold-rolled base material surface by virtue of steel rolling process - Google Patents
Technology for solving incomplete cleaning of acid washing on cold-rolled base material surface by virtue of steel rolling process Download PDFInfo
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Abstract
The invention discloses a technology for solving incomplete cleaning of acid washing on a cold-rolled base material surface by virtue of a steel rolling process, and belongs to the technical field of steel rolling. By virtue of the control on temperature of a steel billet in a furnace, the control on the heating speed, the control on the temperature of the heating furnace and the control on the in-furnace time, the thickness and constituents of a mill scale are changed, residual elements are attached in the mill scale under technical control, before rough rolling and finish rolling, scale removal passes of scale removal water are increased and the pressure of the scale removal water is also increased, so that the mill scale and the surface residual elements are separated from a steel billet base body. The technology has the advantages of meeting the method required by following surface cold rolling, improving the product yield of enterprises, using a lot of cheap iron ore containing a certain amount of residual elements, and lowering the cost before iron making. The contents of residual elements are as follows: Cu is not more than 0.030%, As is not more than 0.0150%, and Sn is not more than 0.010%.
Description
Technical field
The invention belongs to technical field of steel rolling, particularly a kind ofly solve by rolling process the technique that cold rolling base surface acid does not wash clean.
Background technology
In steel, the residual elements such as Cu, As, Sn are because its oxidation potential is less than iron, in steelmaking process, be difficult to remove and enter molten steel completely, therefore in steel manufacture process, can separate out quality and the performance of three kinds of different mechanism of action of enrichment on steel by the solidifying segregation in solidification of molten steel process, in the segregation of crystal boundary and between steel matrix and oxide layer and bring more impact and harm.
In control at present and reduction steel, the countermeasures and method of residual elements mainly contains: solid-state steel scrap preconditioning technique, iron-bearing mineral calcination process technique, batching dilution method, molten iron remove technology, molten steel removes technology and adds other and suppress element.But the impact that glided by steel industry situation, most domestic enterprise ore source points, mixing at present more, be easy to cause the residual elements such as Cu, As in molten iron to increase, the higher surface quality on hot-rolled sheet coil of residual elements in steel has produced more serious impact, has occurred that a large amount of acid does not wash clean phenomenon in cold-rolled process.This phenomenon is apparent is the blackstreak that a lot of residual elements enrichments appear in cold rolled pickling steel sheets surface.
" impact of residual elements on the hot cold rolling coil quality of ripples steel CSP " guarantees that by controlling residual element content in iron ore or steel scrap residual element content in steel billet is lower than certain level from only having proposed in the documents such as the 1st phases " world steel " in 2009, but after the residual element content in steel billet is too high, the method making up does not but have clear and definite relevant report, and more not relevant patent is declared.
Summary of the invention
The object of the present invention is to provide and a kind ofly solve by rolling process the technique that cold rolling base surface acid does not wash clean, in conjunction with the equipment condition at each enterprise's steel rolling scene, according to the formation mechanism of different times iron scale and the difference of removing method, carry out necessary technology controlling and process by the link that respectively affects iron scale formation in steel rolling, reach the effect that alleviates the enrichment of Surfaces of Hot Rolled Strip residual elements, thereby solved not clear problem of cold rolling base surface acid-washing.
The smelting furnace material principal component scope of application of the present invention is cold rolling base, and the main trade mark is that Q195, Q195L, SPHC, 08Al, IF steel, TRIP steel etc. are applicable to cold rolling steel grade, residual element content (Cu≤0.030%, As≤0.0150%, Sn≤0.010%).The technical parameter of processing step and control is as follows:
(1) charging temperature: guarantee that steel billet temperature into stove is at 800～950 ℃;
(2) time inside furnace: the time inside furnace of the first bringing-up section 30～60 minutes, the time inside furnace of the second bringing-up section 25～50 minutes, the time inside furnace of the 3rd bringing-up section 25～50 minutes, soaking zone 20～40 minutes, guarantee steel billet stove heat time total amount 120～180 minutes;
(3) furnace atmosphere: guarantee that the oxygen volumn concentration of flue gas of heating furnace is between 0～2%;
(4) heating-up temperature: the temperature of the first bringing-up section is controlled at 1030～1050 ℃, the temperature of the second bringing-up section is controlled at 1150～1170 ℃, and the temperature of the 3rd bringing-up section is controlled at 1310～1330 ℃, and the temperature of soaking zone is controlled at 1300～1320 ℃;
(5) de-scaling water: the hydraulic pressure of de-scaling water is at 16～20MPa, and de-scaling passage is 5～7 times;
(6) acid washing conditions: descaling bath temperature: 60～80 ℃, pickling time: 40～60s, acid strength (mass percent): 12%～18%.After pickling, requiring inner rating result is qualified (being always divided into 5 grades) at 1 grade or 2 grades.
The main work of the present invention is the control of heating process, by the temperature control to entering stove steel billet, the control of firing rate, the control of furnace temp and the control of time inside furnace, change iron scale thickness with and component form, by technology controlling and process, residual elements are attached in iron scale, before roughing and finish rolling, by increasing the de-scaling passage of de-scaling water, increase the pressure of de-scaling water, make iron scale and surperficial residual elements depart from steel billet matrix, solved cold rolling base surface acid and do not washed clean.Concrete technology flow chart, as shown in Figure 1.
Residual elements are divided three classes by the large I of its oxidation potential in steel, and its oxidation potentials of element bag such as Cu, As, Sn are lower than iron, and the oxidation reaction in the time of steel-making will not relate to these elements, and therefore these residual elements will all accumulate in final steel products.Its oxidation potentials of element such as C, H, N, S, P and iron approach, in the converting process of steel-making, wherein a part is removed oxidized, and in molten steel remaining their compositions at molten steel and slag that depends in part on, both have determined the distribution coefficient of residual elements in molten steel and slag.The 3rd dvielement comprises Pb, Zn, V, Ti, Si, Al, Zr, Mg, Ca and Nb, and its oxidation potential will be higher than iron, and in molten steel converting process, they are first oxidized enters slag and remove in mutually, generally can not enter molten steel.At present about in the residual elements problem in steel, residual elements mainly refer to that the affinity that Cu, As, Sn etc. and the affinity of oxygen are less than iron and oxygen is that oxidation potential is less than iron, be difficult to removal and enter the element of molten steel completely in steelmaking process.Because residual elements can not effectively be removed in the time making steel, therefore in the time that recycling repeatedly, steel can run up to high level, and in the time that these residual element contents reach certain content, may produce obviously impact to some performance of steel, and some other element is not all within the scope of the discussion of residual elements.
The principle of the invention is that oxidation potential based on residual elements is lower than iron, simultaneously the fusing point of the element such as Cu, As, Sn is low, by rational temperature process control, make it in steel manufacture process, avoid the solidifying segregation in solidification of molten steel process, the generation of separating out the phenomenons such as enrichment in the segregation of crystal boundary and between steel matrix and oxide layer.
Cu, As, the fusing point of the elements such as Sn and the eutectic structure that forms between them is between 600 to 800 ℃, therefore to strictly control the charging temperature of heating furnace, guarantee that the charging temperature of continuous casting billet is at 800 ~ 950 ℃, thereby avoid continuous casting billet at High-temperature cooling, in post bake process, due to Cu, As, the oxidation potential energy of the elements such as Sn is lower than iron, oxidizing gas and steel material react, residual elements segregation is at crystal boundary, simultaneously because the preferential oxidation speed of iron is obviously greater than residual elements to the speed spreading in matrix, residual elements are separated out between iron oxide layer and steel matrix layer, in the enrichment gradually of continuous casting billet surface, form low melting point enrichment phase.
The number of the enrichment of element amounts such as Cu, As, Sn and the oxidated layer thickness of billet surface have direct relation, and the enriching quantity of the thicker residual elements of oxidated layer thickness is larger, the more difficult pickling in cold rolling base surface.At the residual elements of billet surface enrichment, major part is because not oxidation, be diffused into the surface of strand and the enriched layer that forms by oxide layer, therefore can control the atmosphere in heating furnace by the oxygen content detecting in flue gas of heating furnace, guarantee that the oxygen content of flue gas of heating furnace is between 0 ~ 2%, thereby guarantee that heating furnace is always weak oxide atmosphere or reducing atmosphere heating.
For the enrichment that reduces residual elements also will guarantee the time of steel billet in heating furnace, therefore to accelerate programming rate, shorten the heat time, thereby reduce the enrichment time of residual elements at billet surface, in syllogic walking beam furnace, the time inside furnace that guarantees the first bringing-up section is less than 60 minutes, the time inside furnace of the second bringing-up section is less than 50 minutes, the time inside furnace of the 3rd bringing-up section is less than 50 minutes, soaking zone is less than 40 minutes, thereby what guarantee steel billet is less than 180 minutes in stove heat time total amount, reach the object that reduces iron scale thickness.
Because iron scale and residual elements and the adhesion of steel billet iron-based body and the porousness of iron scale have much relations, in order to obtain good open texture, need press to the heating-up temperature of the higher steel billet of residual elements the upper limit control of heating furnace ability, the temperature that guarantees the first bringing-up section is controlled at 1030 ~ 1050 ℃, the temperature of the second bringing-up section is controlled at 1150 ~ 1170 ℃, the temperature of the 3rd bringing-up section is controlled at 1310 ~ 1330 ℃, and the temperature of soaking zone is controlled at 1300 ~ 1320 ℃.Thereby guarantee the rational porousness of iron scale, guarantee can be removed in follow-up de-scaling process clean.
In heating furnace, the descaling system of the steel billet of high-temperature heating before by roughing unit and mm finishing mill unit can be removed most iron scale and residual elements, it is clean for the residual elements of low melting point are removed, must strengthen the water spray pressure of de-scaling water system, guarantee that the hydraulic pressure of de-scaling water is between 16 ~ 20MPa, de-scaling passage is 5 ~ 7 times.Large pressure, except improving the peeling off effect of iron scale, can also change by the local temperature that increases casting billet surface, be that surface produces the larger effect of expanding with heat and contract with cold, thereby make the residual elements of billet surface enrichment depart from steel billet matrix.
Compared with prior art, the invention has the beneficial effects as follows:
1, with the residual element content adopting in control iron ore, or compare by the technique of residual element content in reducing molten iron and steel-smelting alloy early stage in steel-making, the present invention has changed the traditional approach that the undesirable cold rolling steel billet of steel-making residual elements control in early stage can only change, propose to meet by steel rolling process control the method for follow-up cold rolling surface requirements, improved the product lumber recovery of enterprise.
2, by this technique, can liberate the raw material control of ironmaking, be convenient to a large amount of low price iron ores that adopt containing a certain amount of residual elements, can obviously reduce the front cost of iron.
Accompanying drawing explanation
Fig. 1 is the flow chart of this process.
The specific embodiment
Concrete example
Chemical composition to SPHC steel billet is as shown in table 1
The chemical composition surplus of the concrete steel billet of table 1 is Fe
Comparative example 1:
1, charging temperature: 650 ℃;
2, time inside furnace: the time inside furnace of the first bringing-up section 68 minutes, the time inside furnace of the second bringing-up section 52 minutes, the time inside furnace of the 3rd bringing-up section 65 minutes, 39 minutes soaking zone time was 224 minutes in stove heat time total amount.
3, furnace atmosphere: the oxygen content of flue gas of heating furnace is 3.0%.
4, heating-up temperature: 1027 ℃ of the temperature of the first bringing-up section, the temperature of the second bringing-up section is controlled at 1143 ℃, and the temperature of the 3rd bringing-up section is controlled at 1283 ℃, and the temperature of soaking zone is controlled at 1280 ℃.
5, de-scaling water: the hydraulic pressure of de-scaling water is 16MPa, de-scaling passage is 3 roads.
Embodiment 1:
1, charging temperature: 810 ℃.
2, time inside furnace: the time inside furnace of the first bringing-up section 42 minutes, the time inside furnace of the second bringing-up section 32 minutes, the time inside furnace of the 3rd bringing-up section 35 minutes, 29 minutes soaking zone time was 138 minutes in stove heat time total amount.
3, furnace atmosphere: the oxygen volumn concentration of heating furnace flue is 1.2%.
4, heating-up temperature: the temperature of the first bringing-up section is controlled at 1042 ℃, the temperature of the second bringing-up section is controlled at 1165 ℃, and the temperature of the 3rd bringing-up section is controlled at 1328 ℃, and the temperature of soaking zone is controlled at 1318 ℃.
5, de-scaling water: the hydraulic pressure of de-scaling water is 18MPa, de-scaling passage is 7 roads.
Other process parameter controls are all identical, adopt the slab after 200mm, be rolled into the band after 3mm, band is found after the pickling of same cold-rolling pickling line, on the belt steel surface that adopts comparative example 1 to produce, has occurred a large amount of black ribbon grains, all has distribution in the upper and lower surface of whole piece band steel, linearly or the undaform of this blackstreak, belt steel surface blackout shades simultaneously, directly affects the surface quality of follow-up cold-rolled process, and rating result is 4 grades.And the belt steel surface light that adopts embodiment 1 to produce, without any blackstreak or spot, rating result is 1 grade.
Finally explanation, above embodiment is only unrestricted so that technical scheme of the present invention to be described.Although the present invention is had been described in detail with reference to preferred embodiment, those of ordinary skill in the art is to be understood that, can carry out the modification in parameter area or be equal to replacement technical scheme of the present invention, and not departing from aim and the scope of technical solution of the present invention, it all should be encompassed in the middle of claim scope of the present invention.
Claims (1)
1. solve by rolling process the technique that cold rolling base surface acid does not wash clean, it is characterized in that, the technical parameter of processing step and control is as follows:
(1) charging temperature: guarantee that steel billet temperature into stove is at 800～950 ℃;
(2) time inside furnace: the time inside furnace of the first bringing-up section 30～60 minutes, the time inside furnace of the second bringing-up section 25～50 minutes, the time inside furnace of the 3rd bringing-up section 25～50 minutes, soaking zone 20～40 minutes, guarantee steel billet stove heat time total amount 120～180 minutes;
(3) furnace atmosphere: guarantee that the oxygen volumn concentration of flue gas of heating furnace is between 0～2%;
(4) heating-up temperature: the temperature of the first bringing-up section is controlled at 1030～1050 ℃, the temperature of the second bringing-up section is controlled at 1150～1170 ℃, and the temperature of the 3rd bringing-up section is controlled at 1310～1330 ℃, and the temperature of soaking zone is controlled at 1300～1320 ℃;
(5) de-scaling water: the hydraulic pressure of de-scaling water is at 16～20MPa, and de-scaling passage is 5～7 times;
(6) acid washing conditions: descaling bath temperature: 60～80 ℃, pickling time: 40～60s, acid strength: 12 quality %～18 quality %; After pickling, inner rating result is qualified at 1 grade or 2 grades;
The smelting furnace material scope of application is cold rolling base, and the trade mark is Q195, Q195L, SPHC, 08Al, residual element content: Cu≤0.030%, As≤0.0150%, Sn≤0.010%.
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| CN104324958A (en) * | 2014-09-24 | 2015-02-04 | 首钢总公司 | Method for overcoming surface landscape painting defects after LCAK steel pickling |
| CN109940043B (en) * | 2019-04-09 | 2020-07-03 | 唐山市德龙钢铁有限公司 | Preparation method of hot rolled strip steel easy to pickle |
| CN114101357A (en) * | 2021-12-01 | 2022-03-01 | 福建三钢闽光股份有限公司 | Heating and descaling method for controlling furnace-generated iron scale of steel for wire rod |
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