CN102041514A - Method for improving surface quality of strip steel after pickling by pickling line - Google Patents

Abstract

The invention relates to a method for improving the surface quality of strip steel after pickling by a pickling line, belonging to the technical field of metal material processing. Technical parameters need to be controlled as follows in the pickling process: cutting off a pre-rinsing section (closing a valve between a 1# rinsing channel and a pre-rinsing channel); increasing the conductivity of rinsing water in a 5# rinsing channel to 10-20 mu S/cm; and lowering the set temperature value of rinsing water in the 5# rinsing channel from 65 DEG C to 40-50 DEG C. By taking several measures different from the control concept of the traditional rinsing process, the invention effectively mitigates the problem that the surface of strip steel is yellowed after pickling and rinsing in case of a low process speed, and simultaneously reduces the consumption of desalted water to a certain extent. Thus, the surface quality of the strip steel is improved, and the production cost is saved.

Description

A kind of pickling unit strip pickling rear surface method for quality of improving

Technical field

The invention belongs to the metal material processing technical field, particularly a kind of pickling unit strip pickling rear surface method for quality of improving.

Background technology

No matter at present comparatively advanced pickling line is pickling unit independently, or pickling milling train associating unit, generally adopts shallow slot turbulent flow continous way chlorohydric acid pickling unit both at home and abroad; The 3-5 of this unit continuous pickling groove can be removed the hot rolled strip scale on surface efficiently.

Remaining acid solution on the strip pickling rear surface after the acid tank exit is extracted by squeezing roller, still leaves about 10～50mL/m on the belt steel surface ²Residual acid solution film, contain the free acid of high level and less Fe2+.Residual acid solution can cause corrosion to band steel matrix Fe on the one hand as not handling; On the other hand, residual acid solution is taken the pH value that can influence emulsion system in the milling train to, and more Cl-can cause the emulsion system demulsifying phenomenon, influences the lubricity of emulsion.For this reason, the carefully residual acid of flushing strip pickling rear surface makes the acid solution that remains in belt steel surface obtain dilution, promptly so-called rinsing process.In rinse cycle, generally guarantee that by controlling last groove rinse water specific conductivity the strip pickling rear surface is rinsed ground enough totally.

For the control of rinsing process, generally believe and use pre-rinsing, and make that the rinsing electrical conductivity of water is low more good more in last rinse tank.Shoudu Iron and Steel Co adopts above-mentioned control thinking, use pre-rinsing and control 5# rinse water specific conductivity generally below 10 μ S/cm, but when process speed (below 60-80m/min) on the low side, the band steel goes out the phenomenon that the surface jaundice still can appear in the rinse tank rear surface, and surface quality is caused disadvantageous effect.

Summary of the invention

The object of the invention is to provide a kind of pickling unit strip pickling rear surface method for quality of improving, and by adjusting rinsing process, strip surface quality is optimized, and has solved the problem of rinsing rear surface jaundice.Concrete technical scheme is the following technical parameter of control in acid cleaning process:

(1) turns off pre-rinsing section (being about to the valve closes of 1# rinse tank) (the present invention implements, and comprises 5 rinse tanks on the existing pickling lines, wherein is provided with pre-rinse tank before the 1# rinse tank) on existing pickling lines to pre-rinsing

(2) improve 5# rinse tank rinsing electrical conductivity of water to 10-20 μ S/cm,

(3) reduce the rinse water temperature, make 5# rinse tank rinse water temperature set(ting)value change 40-50 ℃ into by 65 ℃.

After implementing such scheme, during pickling segment process speed 60-80m/min, belt steel surface jaundice problem is significantly improved, and has effectively improved strip surface quality.

Strip pickling, the jaundice of rinsing rear surface, its reaction mechanism is as follows:

Belt steel surface residual hydrochloric acid corroding metal iron: Fe+2HCl=FeCl2+H2 (1)

The hydrolysis of residual and newly-generated iron protochloride: FeCl2+H2O=Fe (OH) 2+2HCl (2)

The oxidation of ferrous hydroxide: 2Fe (OH) 2+H2O+1/2O2=2Fe (OH) 3 (3)

Fe (OH) 3 is henna throw out, and instability is easily decomposed: Fe (OH) 3=FeO (OH)+H2O (4)

FeO (OH) promptly is a scale, is the basic reason that causes the belt steel surface jaundice.

Above-mentioned reaction mainly occurs in the 1# rinse tank.In the 1# rinse tank, residual acid of belt steel surface and new life's FeCl2 is maximum relatively, so reaction formula (1) and (2) the easiest generation; Simultaneously, the adjacent two row's injector spacings of 1# rinse tank are from the longest relatively, and the band steel just comes out from pickling tank, temperature is higher, these two factors cause when process speed is relatively low, the evaporation easily between adjacent two row's nozzles of belt steel surface moisture, and making that reaction formula (3) (4) is easier carries out.

In addition, the pH value of 1# rinse water is also to reacting the decisive influence that plays 2..When pH value during in the 1.5-4.5 scope, the easiest the carrying out of reaction formula (2); And under strong acid (pH value＜1.5) or highly basic (pH value＞4.5) environment, reaction formula (2) can be suppressed.

Several technical measures that the present invention taked, its effect is respectively:

(1) turns off pre-rinsing.To reduce the de-salted water magnitude of recruitment of 5# rinse tank, the influence that brings is that 5# rinse water specific conductivity increases to some extent, and the pH value of 1# rinse water decreases.Because the reduction (＜1.5) of pH value, reaction formula (2) will be inhibited.

(2) suitably improve 5# rinsing electrical conductivity of water.Part is the result of measure (1), also can reduce the de-salted water magnitude of recruitment of 5# rinse tank simultaneously by the raising of conductivity setpoint to a certain extent.Inhibition same (1) to reaction formula (2).

(3) suitably reduce the rinse water temperature.When process speed is relatively low, will slow down adjacent two velocity of evaporation of arranging belt steel surface moisture between nozzles in the 1# rinse tank, make belt steel surface fully be covered, completely cut off belt steel surface and O by rinse water ₂Contact, restraining effect is played in reaction formula (3), (4).

The present invention is different with the rinsing control thinking of extensively taking, several measures of traditional rinsing process control theory have been taked to be different from: by taking to turn off pre-rinsing, suitably improving 5# rinse tank rinse water specific conductivity and suitably reduce several measures such as rinse water temperature, effectively alleviate the problem (belt steel surface is silvery white in color after making pickling) of strip pickling, the jaundice of rinsing rear surface when process speed is low, reduced the consumption of de-salted water simultaneously to a certain extent.When improving strip surface quality, saved cost.

Description of drawings

Fig. 1 is a 1# rinse water pH value control actual achievement before the process optimization.

Fig. 2 is a 1# rinse water pH value control actual achievement behind the process optimization.

Fig. 3 is a 5# rinse water conductivity value control actual achievement before the process optimization.

Fig. 4 is a 5# rinse water conductivity value control actual achievement behind the process optimization.

Embodiment

As mentioned above: at first, turn off pre-rinsing section; Secondly, suitably improve 5# rinse tank rinsing electrical conductivity of water, by general before optimizing＜10 μ S/cm, be increased between the 10-20 μ S/cm after the optimization (stable back one day measured value be 16.4 μ S/cm, 19.8 μ S/cm, 12.7 μ S/cm, 12.8 μ S/cm, 19.4 μ S/cm and 17.2 μ S/cm); At last, suitably reduce the rinse water temperature, 5# rinse water temperature set(ting)value is by 65 ℃ before optimizing 40-50 ℃ ℃ (eyeball has 42,44,45,48,50 ℃) that are reduced to after the optimization.Effectively alleviate the problem of strip pickling, the jaundice of rinsing rear surface when process speed is low, reduced the consumption of de-salted water simultaneously to a certain extent.

Claims (1)

1. one kind is improved pickling unit strip pickling rear surface method for quality, it is characterized in that the following technical parameter of control in acid cleaning process:

(1) turns off the valve of pre-rinsing section 1# rinse tank to pre-rinsing;

(2) improve 5# rinse tank rinsing electrical conductivity of water to 10-20 μ S/cm;

(3) reduce the rinse water temperature, make 5# rinse tank rinse water temperature set(ting)value change 40-50 ℃ into by 65 ℃.

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