JPH10219486A - Pickling liquid and pickling method - Google Patents

Abstract

(57) [Problem] To eliminate the possibility of generating nitrogen oxides (NOx gas) during pickling treatment as in the conventional pickling treatment using a mixed acid of nitric acid and hydrofluoric acid, and to reduce the concentration of dissolved nitrogen in the waste liquid. Provided is a pickling liquid capable of descaling a difficult-to-descale material in a state where the waste liquid regulation can be sufficiently satisfied without being high, and a pickling method using the pickling liquid. SOLUTION: It is mainly composed of a mixed acid containing hydrochloric acid or sulfuric acid or a mixture of both as a main component and at least a water-insoluble carboxylic acid and a surfactant. In some cases, the mixture further contains hydrofluoric acid or nitrogen oxide (NOx gas). A pickling solution containing a small amount of nitric acid or a nitric acid compound or a water-soluble carboxylic acid which does not generate water, and a pickling method using the pickling solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a scale produced by hot rolling or heat treatment of a metal material such as stainless steel and the like, as a substitute for an ordinary method.
The present invention relates to a pickling solution and a pickling method suitable for pickling and removing (that is, descaling) a material and a scale of heat history which are difficult to remove by a normal method.

[0002]

2. Description of the Related Art When descaling the surface of a metal material such as stainless steel, the scale is usually relaxed by a molten salt (hereinafter referred to as "salt treatment") and pickled by a mixed acid of nitric acid and hydrofluoric acid. Often implemented in combination with

[0003]

However, nitric acid +
The mixed acid of hydrofluoric acid may generate nitrogen oxides (NOx gas) at the time of pickling, and has a problem that it is difficult to satisfy a waste liquid treatment standard due to a large amount of dissolved nitrogen in the waste liquid. As in the conventional pickling of nitric acid and hydrofluoric acid, nitrogen oxide (NOx gas) is not generated during pickling, and the amount of dissolved nitrogen in the waste liquid is reduced to avoid the difficulty of waste liquid treatment. There was a problem to be able to easily regulate the amount of dissolved nitrogen in water.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a method for producing nitrogen oxides (N
Ox gas) can be prevented from being generated, and a waste liquid treatment can be easily performed to meet a waste liquid treatment standard, and depending on the scale properties, a pickling solution and a pickling method capable of good descaling without salt treatment are provided. It is intended to be.

[0005]

According to the present invention, the pickling solution according to the present invention contains hydrochloric acid or sulfuric acid or a mixture of both, as a main component, and is mixed with a water-insoluble carboxylic acid and an interface. It is characterized by comprising a mixed acid containing at least an activator.

Further, the pickling solution according to the present invention can be composed of a mixed acid containing hydrofluoric acid in the mixed acid of claim 1, as described in claim 2, or
As described in claim 3, the mixed acid according to claim 1 or 2 contains a small amount of nitrogen oxide (N
Ox gas) can be composed of nitric acid or a mixed acid containing a nitric acid compound in such an amount that does not generate Ox gas), or as defined in claim 4, according to claim 1, 2, or 3 It may be composed of a mixed acid containing a water-soluble carboxylic acid.

The pickling method according to the present invention is, as described in claim 5, a mixed acid containing hydrochloric acid or sulfuric acid or a mixture of both as a main component and at least a water-insoluble carboxylic acid and a surfactant. It is characterized by using.

In the pickling method according to the present invention, as described in claim 6, a mixed acid containing hydrofluoric acid can be used for the mixed acid described in claim 5, or Claim 5 or 6 as described in claim 7.
The mixed acid according to the above may be a mixed acid containing a small amount of nitric acid or a nitric acid compound (ie, an amount that does not generate nitrogen oxides (NOx gas) during pickling). Claims 5 and 6 as described.
Alternatively, a mixed acid containing a water-soluble carboxylic acid may be used as the mixed acid according to claim 7, and in some cases, the pickling method according to claims 5 to 8 may be appropriately repeated or performed in combination. it can.

The pickling solution and the pickling method according to the present invention include:
Although having the above-described configuration, it will be described in further detail below.

Hydrochloric acid or sulfuric acid or a mixed solution of both The hydrochloric acid or sulfuric acid or a mixed acid of both contributes to the dissolution of FeO in the scale and the base immediately below the scale, and is therefore the main component in the pickling solution.

If the amount of hydrochloric acid or sulfuric acid or a mixed acid of both is small, the time required for pickling tends to be long. Therefore, it is more preferable that the amount is 5 wt / vol% or more. If the amount is too high, the pickling rate tends to be not so much improved, so that 30 wt / v
ol% or less, more preferably 10 to 25 wt.
/ Vol% is more desirable.

Water-insoluble carboxylic acid The water-insoluble carboxylic acid reacts with a surfactant to make it water-soluble, thereby forming a chelate with a dissolved metal ion, thereby forming a metal ion in the vicinity of the substrate surface. Since it is an agent that contributes to preventing the occurrence of rough skin and pitting due to the concentration of the acid, it is added to the pickling solution in an appropriate amount.

The water-insoluble carboxylic acid is selected from the first group (having a benzene nucleus) and the second group (having a straight chain) as shown in Table 1. You can choose to use.

[0014]

[Table 1]

In this case, if the amount of the water-insoluble carboxylic acid is too small, the effect of preventing skin roughness and pitting due to the concentration of metal ions near the surface of the substrate becomes insufficient, so that the content is 0.01 wt / vol% or more. More preferably, the content is more preferably 0.1 wt / vol% or more. However, since foaming increases when blended more than necessary, the content is more preferably 1.0 wt / vol% or less. More preferably, the content is 0.2 wt / vol% or less.

Surfactant Since the surfactant is a component that contributes to the water-solubility of the water-insoluble carboxylic acid, the surfactant is appropriately added to the pickling solution.

[0017] Such surfactants include:
It can be appropriately selected and blended from anionic or nonionic compounds as exemplified in Table 2.

[0018]

[Table 2]

In this case, the amount of the surfactant is desirably equal to or more than the amount necessary for making the water-insoluble carboxylic acid soluble, that is, the concentration of the water-insoluble carboxylic acid. Since the foaming increases when blended as described above, the concentration is more preferably about three times or less the concentration of the water-insoluble carboxylic acid.

◎ Hydrofluoric acid It is possible to use a pickling solution in which hydrofluoric acid is added to a mixed acid containing hydrochloric acid or sulfuric acid or a mixture of both as a main component and at least a water-insoluble carboxylic acid and a surfactant. The hydrofluoric acid contributes to the dissolution of hydrofluoric acid-soluble components such as SiO ₂ in the scale and the improvement of the permeability of the mixed acid.

Therefore, in some cases, this hydrofluoric acid can be mixed in an appropriate amount in the mixed acid. However, if the mixing amount is too large, the effect cannot be improved so much.
1% or less (that is, in the range of 0 to 10 wt / vol%)
It is preferable to set the weight to 5 wt / vo from the viewpoint of economy.
1% or less (that is, in the range of 0 to 5 wt / vol%).

◎ A small amount of nitric acid or a nitric acid compound In a mixed acid containing hydrochloric acid or sulfuric acid or a mixture of both as a main component and at least a water-insoluble carboxylic acid and a surfactant, and optionally hydrofluoric acid as described above. It is also possible to prepare a pickling solution containing a small amount of nitric acid or a nitric acid compound in a mixed acid containing
It is effective in controlling the oxidation-reduction potential (ORP) and contributes to keeping the oxidation-reduction potential in the active dissolution potential region.

[0023] Such nitric acid or nitric acid compound can be appropriately selected and compounded from those exemplified in Table 3.

[0024]

[Table 3]

In this case, if the compounding amount of nitric acid or a nitric acid compound is too large, nitrogen oxides (NOx gas) are generated at the time of pickling or a waste liquid having a high concentration of dissolved nitrogen cannot be obtained to satisfy the waste liquid treatment standard. Therefore, it is necessary to take a countermeasure against dissolved nitrogen. Therefore, 1 w which is smaller than the generation level of nitrogen oxides (NOx gas) as nitrate is small.
t / vol% or less (that is, in the range of 0 to 1 wt / vol%), more preferably 0.1 to 0.2 wt%.
/ Vol% is more desirable.

◎ Water-soluble carboxylic acid In a mixed acid containing hydrochloric acid or sulfuric acid or a mixture thereof as a main component and containing at least a water-insoluble carboxylic acid and a surfactant, and in some cases, hydrofluoric acid and / or Alternatively, a pickling solution containing a water-soluble carboxylic acid in a mixed acid also containing nitric acid or a nitric acid compound can be used, but the water-soluble carboxylic acid is formed by forming a complex salt with a dissolved metal ion. This contributes to improving the life of the pickling solution.

[0027] Such a water-soluble carboxylic acid can be appropriately selected from those exemplified in Table 4 and blended.

[0028]

[Table 4]

In this case, even if the amount of the water-soluble carboxylic acid is too large, the effect is not so much improved, and considering the economic efficiency, it is not more than 10 wt / vol% (that is, 0 to 0%).
More preferably, it is set to 10 wt / vol%.

[0030]

Embodiment 1 This embodiment 1 shows an example of pickling in which the salt treatment is omitted.

That is, austenitic stainless steels SUS 304, SUS XM7, S
US 316 as a target steel, and ferritic stainless steel SUS 430 and martensitic stainless steel SUS 403 as shown in Table 6 as target steels, the histories shown in Tables 5 and 6 (that is, solution heat treatment, Table 5 for steel materials with hot rolling and annealing)
And pickling treatment was performed using a mixed acid having a composition shown in Table 6.

When the descaling state after the pickling treatment was performed by changing the pickling treatment conditions (temperature and time), the results shown in Tables 5 and 6 were obtained.

As shown in Tables 5 and 6, in the pickling method using the pickling solution according to the present invention, pickling (descaling) of hard-to-descale stainless steel can be carried out well without salt treatment. Was possible.

[0034]

[Table 5]

[0035]

[Table 6]

Embodiment 2 This embodiment 2 shows a case in which pickling is performed after the salt treatment.

That is, austenitic stainless steels SUS XM7 and SUS 310S as shown in Table 7 are used as target steels, and ferritic stainless steels SUS 430 and martensitic stainless steel SUS 403 shown in Table 8 are used as target steels. The histories shown in Tables 7 and 8 (that is, hot rolling, solution heat treatment,
(Annealed), a pickling treatment was performed using a mixed acid having the same composition as shown in Tables 7 and 8.

Then, the descaling state after the pickling treatment under different pickling treatment conditions (temperature, time) was examined. The results are shown in Tables 7 and 8 as well.

As shown in Tables 7 and 8, in the pickling method using the pickling solution according to the present invention, the pickling (descaling) of the non-descalable stainless steel can be carried out well together with the salt treatment. It was possible.

[0040]

[Table 7]

[0041]

[Table 8]

Embodiment 3 This embodiment 3 shows a case where a steel type other than stainless steel is pickled.

That is, austenitic heat-resistant steel AMS 5735, martensitic heat-resistant steel SUH 11, and austenitic heat-resistant steel SUH 660 as shown in Table 9
And high-speed tool steels SKH 51, SKH 59, corrosion-resistant heat-resistant superalloy NCF as shown in Table 10
750 as a target steel, and for materials having the histories shown in Tables 9 and 10 (ie, solution heat treatment, annealing, salt, and hot rolling), respectively, Tables 9 and 10
An acid pickling treatment was carried out using a mixed acid having the composition shown in FIG.

When the descaling state after the pickling treatment was performed by changing the pickling treatment conditions (temperature, time), the results shown in Tables 9 and 10 were also obtained.

As shown in Tables 9 and 10, in the pickling method using the pickling solution according to the present invention, it was possible to satisfactorily perform pickling (descaling) of a material that is difficult to scale. .

[0046]

[Table 9]

[0047]

[Table 10]

[0048]

According to the present invention, the pickling solution according to the present invention contains hydrochloric acid or sulfuric acid or a mixture thereof as a main component, and contains a water-insoluble carboxylic acid and a surfactant. Since it is made of a mixed acid, it does not generate nitrogen oxides (NOx gas) during the pickling treatment as in the case of performing pickling using a conventional mixed acid of nitric acid and hydrofluoric acid, and
Without increasing the concentration of dissolved nitrogen in the waste liquid, make the waste liquid treatment regulations fully satisfactorily satisfied, and make the surface of metallic materials such as stainless steel, heat-resistant steel, high-speed tool steel, high alloy steel, titanium, etc. difficult to scale. Can be remarkably easily descaled, and descaling without the salt treatment is also possible. In this case, it is possible to reduce the energy consumption and the sludge treatment cost by omitting the salt treatment. This provides a very excellent effect that the surface quality, especially the occurrence of rough surface and pitting, can be prevented to obtain a good surface quality.

And, as described in claim 2,
By using a mixed acid containing hydrofluoric acid in the mixed acid according to claim 1, it is possible to dissolve a hydrofluoric acid-soluble component such as SiO _{2 in} the scale and to improve the permeability of the mixed acid. Significant effects are achieved.

Further, as described in the third aspect, it is possible to control the oxidation-reduction potential by using a mixed acid containing a small amount of nitric acid or a nitric acid compound in the mixed acid according to the first or second aspect. At the same time, an extremely excellent effect that the oxidation-reduction potential can be maintained in the active dissolution potential region is obtained.

Further, as described in the fourth aspect, the mixed acid according to the first, second or third aspect comprises a mixed acid containing a water-soluble carboxylic acid, so that dissolved metal ions and The formation of the complex salt has a remarkably excellent effect that the life of the pickling solution can be improved.

In the pickling method according to the present invention, as described in claim 5, a mixed acid containing hydrochloric acid or sulfuric acid or a mixture of both as a main component and a water-insoluble carboxylic acid and a surfactant is used. Since it is used, the above-described effect based on claim 1 is provided.

And, as described in claim 6,
By using a mixed acid containing hydrofluoric acid as the mixed acid according to the fifth aspect, the effect described in the second aspect can be obtained.

Further, as described in claim 7, by using a mixed acid containing a small amount of nitric acid or a nitric acid compound in the mixed acid of claim 5 or 6, The effects described below are provided.

Further, as described in claim 8, by using a mixed acid containing a water-soluble carboxylic acid in the mixed acid according to claim 5, 6 or 7, the above-mentioned claim 4 is used. According to the present invention, the effects described above are provided.

Claims (8)

[Claims] 1. A pickling solution comprising hydrochloric acid or sulfuric acid or a mixed solution of both as a main component, and a mixed acid containing a water-insoluble carboxylic acid and a surfactant. 2. A pickling solution comprising the mixed acid according to claim 1 containing hydrofluoric acid. 3. A pickling solution comprising a mixed acid containing a small amount of nitric acid or a nitric acid compound in the mixed acid according to claim 1 or 2. 4. A pickling solution comprising a mixed acid containing a water-soluble carboxylic acid in addition to the mixed acid according to claim 1, 2, or 3. 5. A pickling method characterized by using a mixed acid containing hydrochloric acid or sulfuric acid or a mixture of both as a main component and a water-insoluble carboxylic acid and a surfactant. 6. A pickling method comprising using a mixed acid containing hydrofluoric acid as the mixed acid according to claim 5. 7. A pickling method comprising using a mixed acid containing a small amount of nitric acid or a nitric acid compound as the mixed acid according to claim 5 or 6. 8. A pickling method characterized by using a mixed acid containing a water-soluble carboxylic acid as the mixed acid according to claim 5, 6 or 7.