CN102041514B - 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 method of improving surface quality behind the pickling unit strip pickling

Technical field

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

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 is gone up on the surface behind the strip pickling, 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 on surface behind the flushing strip pickling makes the acid solution that remains in belt steel surface obtain dilution, promptly so-called rinsing process.In rinse cycle, generally guarantee that through controlling last groove rinse water specific conductivity the surface is rinsed ground enough totally behind the strip pickling.

For the control of rinsing process, generally believe and use prebleaching to wash, 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 prebleaching to wash 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 surface behind the rinse tank, and surface quality is caused disadvantageous effect.

Summary of the invention

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

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

(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.

Surface jaundice after strip pickling, the rinsing, its reaction mechanism is following:

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 unstable being prone to 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, and the evaporation easily between adjacent two row's nozzles of belt steel surface moisture makes reaction formula (3) (4) carry out more easily.

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) turning off prebleaching washes.With the de-salted water magnitude of recruitment that reduces the 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 through 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 in the 1# rinse tank velocity of evaporation of belt steel surface moisture between adjacent two row's nozzles, make belt steel surface by rinse water fully cover, isolated belt steel surface and O 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: wash, suitably improve several measures such as 5# rinse tank rinse water specific conductivity and suitable reduction rinse water temperature through taking to turn off prebleaching; Effectively alleviate the problem (belt steel surface is silvery white in color after making pickling) that after strip pickling, the rinsing turned to be yellow in the surface when process speed was low, reduced the consumption of de-salted water simultaneously to a certain extent.When improving strip surface quality, practiced thrift 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 stated: at first, turn off the prebleaching section of washing; Secondly; Suitably improve 5# rinse tank rinsing electrical conductivity of water; By general＜10 μ S/cm before optimizing, 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 that after strip pickling, the rinsing turned to be yellow in the surface when process speed was low, reduced the consumption of de-salted water simultaneously to a certain extent.

Claims (1)

1. a method of improving surface quality behind the pickling unit strip pickling is characterized in that, the following technical parameter of control in acid cleaning process:

(1) turns off the valve that the prebleaching section of washing 1# rinse tank is washed to prebleaching;

(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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