JP2017088726A - Descaling promotion additive for alloy steel, acid cleaning liquid composition using the same, and acid cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a descaling promotion additive capable of swiftly performing the descaling of alloy steel, and further having no generation of harmful gas such as hydrogen sulfide, and an acid cleaning method.SOLUTION: Provided is a descaling promotion additive comprising one or more kinds selected from benzyl thiocyanate, trimethyl thiourea, tetramethyl thiourea and 3-mercapto-1-propane sulfonic acid, and also provided is an acid cleaning composition containing the promotion additive.SELECTED DRAWING: None

Description

  TECHNICAL FIELD The present invention relates to an alloy steel descaling promoting additive, an acid cleaning liquid composition using the same, and an acid cleaning method.

  In general, steel materials are subjected to hot rolling and cold rolling on slabs and processed to a desired product thickness, and then subjected to annealing and quenching treatment in a continuous annealing line to control the steel structure. .

  In general, an oxide film such as a mill scale is attached to the surface of a metal hot-rolled material such as a hot-rolled steel sheet or a metal material subjected to heat treatment. It is necessary to remove this oxide film. In order to remove the scale adhering to these metal surfaces, inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, sulfamic acid, nitric acid and hydrofluoric acid, Pickling with a mixture, an organic acid such as oxalic acid or citric acid is performed.

However, it is difficult to remove the oxide film or scale that adheres firmly, and a considerably long pickling time is required to completely remove the oxide film or scale by pickling.
Conventionally, in order to solve these problems, a method of adding a surfactant (Patent Document 1), a method of adding an oxidizing agent and a corrosion inhibitor (Patent Document 2), a method of adding a reducing agent (Patent Document 3), etc. Has been proposed. Furthermore, a method of adding an organic sulfur compound (Patent Document 4) has been proposed.

  In the case of organic sulfur compounds containing mercapto groups, which are relatively effective, another problem is that these compounds partially decompose during pickling to produce hydrogen sulfide, which has a significant adverse effect on the environment. Degradation of the quality. As a method for preventing this, a method (Patent Document 5) is proposed in which a hydrogen sulfide capturing component for capturing generated hydrogen sulfide is contained.

  In the method using the mercapto group-containing organic sulfur compound of Patent Document 5, there are examples where it is used as a pickling accelerator (descaling accelerator), but most of them are acid pickling conditions of 80 to 95 ° C. Decomposition begins in the liquid, generating hydrogen sulfide. The generation of hydrogen sulfide significantly deteriorates the working environment, and further, the surface of the steel material may be discolored to black to deteriorate the quality.

  In addition, the hydrogen sulfide trapping component that traps hydrogen sulfide is not sufficient because its effect decreases with time.

  Moreover, the generation of hydrogen sulfide due to partial decomposition of the mercapto group-containing organic sulfur compound is not known so far, and differs depending on the type of acid, the concentration of the compound, and the temperature, and cannot be predicted in advance. Therefore, there is also a problem that the behavior under actual acid cleaning conditions must be obtained by experiment for each compound.

  In recent years, there has been a rapid increase in demand for steel materials exhibiting high strength and excellent ductility and workability for the purpose of reducing the weight of home appliances, building materials, automobiles, etc. Low alloy steel materials containing relatively large amounts of Mn, Cr, etc. are used. In the case of alloy steel materials containing relatively large amounts of Si, Mn, Cr, the surface of the steel material is oxidized during hot rolling or annealing. In the acid cleaning performed thereafter, a scale that is extremely difficult to dissolve in an acid is formed in the product, Mn-based oxide, Cr-based oxide, or a composite oxide thereof.

  Therefore, in such a low alloy steel, the scale generated by heat treatment or the like becomes stronger than in the case of normal steel, so that the pickling rate is significantly reduced. Therefore, the methods described in Patent Documents 1 to 3 cannot sufficiently cope with the descaling of the low alloy steel material.

JP-A-57-198273 JP 63-203780 A JP 47-34122 A JP-A-5-33171 JP 2006-183116 A

From this point of view, the present inventors proceeded with research on a descaling agent that has a high descaling speed even in an alloy steel material containing a relatively large amount of Si, Mn, and Cr, and generates extremely little hydrogen sulfide gas. It has been found that thiocyanate, trimethylthiourea, tetramethylthiourea and 3-mercapto-1-propanesulfonic acid have an excellent descaling promoting effect, and that an acid cleaning liquid containing these components is an excellent acid cleaning liquid composition. The present invention has been completed.
That is, the object of the present invention is to quickly perform descaling from a low alloy steel having a relatively low content of alloy elements such as Si, Mn, and Cr to a medium to high alloy steel having a relatively high content. It is another object of the present invention to provide a descaling accelerating additive that does not generate harmful gases such as hydrogen sulfide, and to provide an acid cleaning liquid composition and an acid cleaning method using the additive.

  The present invention relates to a descaling accelerating additive that promotes descaling in acid cleaning of an alloy steel, and is selected from benzyl thiocyanate, trimethyl thiourea, tetramethyl thiourea and 3-mercapto-1-propane sulfonic acid 1 A descaling promoting additive characterized by containing a seed or more.

  Furthermore, the present invention is an acid cleaning liquid composition comprising an acid cleaning liquid and the descaling promoting additive described above.

  In addition, the present invention is characterized in that a total of 1 to 1000 ppm of one or more selected from the above-mentioned benzyl thiocyanate, trimethylthiourea, tetramethylthiourea and 3-mercapto-1-propanesulfonic acid is contained.

  Further, the present invention is characterized in that the acid cleaning solution is a hydrochloric acid cleaning solution or one or more organic acid cleaning solutions selected from citric acid, formic acid, glycolic acid or malonic acid.

  Further, the present invention is characterized in that the alloy steel contains 0.3 to 10 wt% in total of Si, Mn and Cr as alloy elements.

  Furthermore, the present invention is an acid cleaning method characterized in that descaling is performed by bringing the above-described acid cleaning liquid composition into contact with an alloy steel.

  Moreover, this invention uses the acid washing | cleaning liquid composition in which 1 or more types selected from the said benzyl thiocyanate, trimethylthiourea, tetramethylthiourea, and 3-mercapto-1-propanesulfonic acid are contained in total in 1-1000 ppm. Features.

Further, the invention is characterized in that the acid cleaning liquid is a hydrochloric acid cleaning liquid.
Further, the invention is characterized in that the acid cleaning liquid is one or more organic acid cleaning liquids selected from citric acid, formic acid, glycolic acid or malonic acid.

  Further, the present invention is characterized in that the alloy steel contains 0.3 to 10 wt% in total of Si, Mn and Cr as alloy elements.

  According to the present invention, a descaling accelerator containing one or more selected from benzyl thiocyanate, trimethyl thiourea, tetramethyl thiourea and 3-mercapto-1-propanesulfonic acid is added to the acid cleaning solution to remove the alloy steel. By performing the scale, it is possible to provide an acid cleaning liquid composition and a cleaning method that increase the descaling speed and generate extremely little hydrogen sulfide.

  The present invention relates to a descaling promoting additive for removing scale which is an oxide film formed on the surface of an alloy steel, and includes benzyl thiocyanate, trimethylthiourea and tetramethylthiourea and 3-mercapto-1-propanesulfonic acid. A descaling promoting additive containing at least one selected from the group consisting of acid cleaning solution compositions and acid cleaning methods using the descaling promoting additive.

  The descaling promoting additive of the present invention comprises at least one of benzyl thiocyanate, trimethylthiourea and tetramethylthiourea and 3-mercapto-1-propanesulfonic acid (hereinafter, individual compounds may be referred to as additive components). Including.

  In the descaling promoting additive of the present invention (hereinafter sometimes referred to as additive), each of the additive components may contain one kind, or may contain two or more kinds, and 3 Even if it contains a kind, you may contain all four kinds.

  Moreover, when it contains 2-4 types, what ratio may be sufficient as the ratio. The descaling promoting additive of the present invention may contain a medium such as water, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and the like in addition to the above components. 0.1 to 99.99% is preferable.

  The additive of the present invention can be produced by mixing one or more of the above-mentioned additive components with a medium by a known means as appropriate.

  The mixing temperature can be carried out under cooling to warming, and the order of mixing is not particularly limited.

  The acid cleaning liquid composition of the present invention (hereinafter sometimes referred to as composition) is selected from benzyl thiocyanate, trimethylthiourea, tetramethylthiourea and 3-mercapto-1-propanesulfonic acid as additives in the acid cleaning liquid. 1 or more types.

  Examples of the acid in the acid cleaning liquid usually include inorganic acids or organic acids. As for the inorganic acid, a hydrochloric acid cleaning solution or a sulfuric acid cleaning solution is preferable. As for the organic acid, one or more organic acid cleaning solutions selected from citric acid, formic acid, glycolic acid or malonic acid are preferable.

  In the case of a hydrochloric acid cleaning solution, the concentration is 10 g / L or more and 350 g / L or less, preferably 20 g / L or more and 200 g / L or less. If it is less than 10 g / L, the descaling time becomes very long, and if it exceeds 300 g / L, the solubility of the scale becomes small, the descaling rate becomes rapidly slow, and it is economically inefficient.

  In the case of an organic acid cleaning solution, the concentration of one or more selected from citric acid, formic acid, glycolic acid or malonic acid is 10 g / L or more and 200 g / L or less, preferably 30 g / L or more and 150 g / L. It is as follows. If it is less than 10 g / L, the descaling time becomes very long, and if it exceeds 200 g / L, the solubility of the scale becomes small, the descaling rate becomes rapidly slow, and it is economically inefficient.

  The additive in the composition of the present invention is added so as to be contained in 1 L of the acid cleaning liquid composition in an amount of 1 ppm to 1000 ppm, preferably 10 to 500 ppm. If it is less than 1 ppm, the effect of promoting descaling is not recognized. Moreover, even if it exceeds 1000 ppm, the effect hardly increases.

  The acid cleaning liquid composition of the present invention may further contain a corrosion inhibitor that suppresses corrosion of the steel surface during acid cleaning, if necessary. As such a corrosion inhibitor, a commercially available corrosion inhibitor can be used as long as it does not exhibit an adverse interaction with the descaling accelerator.

  For example, when hydrochloric acid is used as the acid, Ibit No. 711NH-2 (trade name, manufactured by Asahi Chemical Industry Co., Ltd.), Ibit No. 30AR (trade name, manufactured by Asahi Chemical Industry Co., Ltd.) is suitable.

  The composition of this invention can be manufactured by mixing the said acid cleaning liquid, an additive, and a corrosion inhibitor as needed by a well-known means suitably.

  The mixing temperature can be carried out under cooling to warming, and the order of mixing is not particularly limited.

  In the present invention, acid cleaning of the alloy steel can be performed by bringing the alloy steel into contact with the composition of the present invention.

  The alloy steel to be cleaned with the composition of the present invention is not particularly limited as long as it is an alloy steel containing Cr, Si, and Mn. Includes alloy steel containing 0.5 to 10 wt%, more preferably 1 to 10 wt%. Specifically, chromium steel having a composition obtained by adding several percent of Cr to carbon steel, STB steel, Si, Examples thereof include high-tensile steel containing a relatively large amount of Mn.

  Examples of such alloy steels include STB steel such as STBA12, STBA13, STBA20, STBA22, STBA23, STBA24, STBA5, STBA6, JFE-HITEN590, JFE-HITEN980, JFE-HITEN980, JFE-HITEN570E2, JFE-HITEN580E2, , JFE-HITEN590E, JFE-HITEN590SL, JFE-HYD960LE and other high-tensile steels, and SCr415, SCr420, SCr440 and SCr445 and other chromium steels. Further examples include ordinary steels such as SS400, SS540, and hot rolled mild steel SPHC.

  Examples of the method of bringing the acid cleaning solution composition into contact with the alloy steel include a method of immersing the alloy steel in the acid cleaning solution composition, a method of spraying the acid cleaning solution composition onto the alloy steel, and a method of showering. Other methods may be used.

  Specific processes that can be applied include a continuous pickling process performed on steel strip after hot rolling, an acid cleaning process in which an acid cleaning solution is introduced into an apparatus such as a boiler, and a grating material. And the like, and a batch acid cleaning process in which cleaning is performed by immersing the substrate directly in the pickling solution.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this Example.

Example 1
100 g of benzyl thiocyanate (manufactured by Toyobo Co., Ltd.) was dissolved in 1 liter of water to obtain a descaling addition accelerator. Next, hydrochloric acid and ferrous chloride were added and dissolved in 1 L of water so that hydrochloric acid was contained at 10 wt% and ferrous ion was contained at 70 wt% to prepare an acid cleaning solution. Subsequently, the descaling promoting additive was added to the acid cleaning solution to obtain an acid cleaning solution composition containing 50 ppm of benzyl thiocyanate. Furthermore, a corrosion inhibitor inhibitor 711NH-2 (trade name, manufactured by Asahi Chemical Industry Co., Ltd.) was added to this acid cleaning liquid composition so as to contain 500 ppm.

  This acid cleaning liquid composition was heated to 85 ° C. and maintained at this temperature, and as a steel alloy material, chromium steel after hot rolling having a size of 3 cm × 3 cm (SCr420 / Cr: 0.9 to 1.2%, Si : 0.15-0.35%, Mn: 0.6-0.9%). Evaluation was performed by the following method. The results are shown in Table 1.

Example 2
The acid was washed and descaled in the same manner as in Example 1 except that the acid washing liquid composition was 10 ppm of benzyl thiocyanate. The results are as shown in Table 1.

Example 3
The acid was washed and descaled in the same manner as in Example 1 except that the acid washing liquid composition was 1000 ppm of benzyl thiocyanate. The results are as shown in Table 1.

Example 4
The descaling was performed by acid washing in the same manner as in Example 1 except that trimethylthiourea was used as the descaling promoting additive. The results are as shown in Table 1.

Example 5
The descaling was performed by acid washing in the same manner as in Example 1 except that tetramethylthiourea was used as the descaling promoting additive. The results are as shown in Table 1.

Example 6
Descaling was carried out by acid washing in the same manner as in Example 1 except that 3-mercapto-1-propanesulfonic acid was used as the descaling promoting additive. The results are as shown in Table 1.

Example 7
Descaling was carried out in the same manner as in Example 1 except that 25 ppm of trimethylthiourea and 25 ppm of tetramethylthiourea were used as descaling promoting additives. The results are as shown in Table 1.

Example 8
Descaling was performed in the same manner as in Example 1 except that 20 ppm of trimethylthiourea, 20 ppm of tetramethylthiourea, and 10 ppm of tetramethylthiourea were used as descaling promoting additives. The results are as shown in Table 1.

Example 9
The acid was washed and descaled in the same manner as in Example 1 except that a 10% citric acid washing solution was used as the acid washing solution. The results are as shown in Table 1.

Example 10
The acid was washed and descaled in the same manner as in Example 1 except that 10% formic acid was used as the acid washing and trimethylthiourea was used as the descaling promoting additive. The results are as shown in Table 1.

Example 11
The acid was washed and descaled in the same manner as in Example 1 except that a 10% glycolic acid washing solution was used as the acid washing solution and trimethylthiourea was used as the descaling promoting additive. The results are as shown in Table 1.

Example 12
The acid was washed and descaled in the same manner as in Example 1 except that 10% malonic acid was used as the acid washing and trimethylthiourea was used as the descaling promoting additive. The results are as shown in Table 1.

Example 13
As alloy steel, STB steel (STBA20 / Cr: 0.5-0.8%, Si: 0.1-0.5%, Mn: 0.3-0.6%) is targeted for acid cleaning, descaling The acid was washed and descaled in the same manner as in Example 1 except that trimethylthiourea was used as the accelerating additive. The results are as shown in Table 1.

Example 14
STB steel (STBA25 / Cr: 4.0-6.0%, Si: 0.5% or less, Mn: 0.3-0.6%) as an acid steel, and descaling acceleration additive As in Example 1, acid washing and descaling were performed except that trimethylthiourea was used. The results are as shown in Table 1.

Comparative Example 1
The acid was washed and descaled in the same manner as in Example 1 except that the descaling agent was not used. The results are as shown in Table 1.

Comparative Example 2
The acid was washed and descaled in the same manner as in Example 1 except that ammonium thiosulfate was used as the descaling agent. The results are as shown in Table 1.

Comparative Example 3
The acid was washed and descaled in the same manner as in Example 1 except that 1,3-dimethylthiourea was used as the descaling agent. The results are as shown in Table 1.

Comparative Example 4
The acid was washed and descaled in the same manner as in Example 1 except that thiourea was used as the descaling agent. The results are as shown in Table 1.

Comparative Example 5
The acid was washed and descaled in the same manner as in Example 1 except that dibutylthiourea was used as the descaling agent. The results are as shown in Table 1.

Comparative Example 6
The acid was washed and descaled in the same manner as in Example 7 except that the descaling agent was not used. The results are as shown in Table 1.

Comparative Example 7
The acid was washed and descaled in the same manner as in Example 8 except that the descaling agent was not used. The results are as shown in Table 1.

Comparative Example 8
The acid was washed and descaled in the same manner as in Example 9 except that the descaling agent was not used. The results are as shown in Table 1.

Comparative Example 9
The acid was washed and descaled in the same manner as in Example 10 except that the descaling agent was not used. The results are as shown in Table 1.

Comparative Example 10
The acid was washed and descaled in the same manner as in Example 11 except that the descaling agent was not used. The results are shown in Table 1.

Comparative Example 11
The acid was washed and descaled in the same manner as in Example 12 except that the descaling agent was not used. The results are as shown in Table 1.

<Evaluation method>
Descaling time The time from when the sample was immersed until the surface scale was completely removed was measured by visual judgment.

Hydrogen sulfide generation amount After the sample was immersed, the gas detector tube No. Hydrogen sulfide was measured using 120SE (manufactured by Komyo Chemical Co., Ltd.).

Claims (11)

  A descaling promoting additive for promoting descaling in acid cleaning of alloy steel, comprising at least one selected from benzyl thiocyanate, trimethylthiourea, tetramethylthiourea and 3-mercapto-1-propanesulfonic acid A descaling promoting additive characterized by   An acid cleaning liquid composition comprising the acid cleaning liquid and the descaling promoting additive according to claim 1.   The acid cleaning solution according to claim 2, wherein a total of 1 to 1000 ppm of one or more selected from the benzyl thiocyanate, trimethylthiourea, tetramethylthiourea and 3-mercapto-1-propanesulfonic acid is contained. Composition.   The acid cleaning liquid composition according to claim 2 or 3, wherein the acid cleaning liquid is a hydrochloric acid cleaning liquid or an organic acid cleaning liquid.   The acid cleaning liquid composition according to claim 2 or 3, wherein the acid cleaning liquid is at least one organic acid cleaning liquid selected from citric acid, formic acid, glycolic acid, or malonic acid.   The pickling solution composition according to any one of claims 2 to 5, wherein the alloy steel is an alloy steel containing 0.3 to 10 wt% of Si, Mn, and Cr as alloy elements in total.   An acid cleaning method comprising performing descaling by bringing the acid cleaning liquid composition according to claim 2 into contact with an alloy steel.   The acid cleaning liquid composition comprising 1 to 1000 ppm in total of at least one selected from the above-mentioned benzyl thiocyanate, trimethylthiourea, tetramethylthiourea and 3-mercapto-1-propanesulfonic acid. 8. The acid cleaning method according to 7.   The acid cleaning method according to claim 7 or 8, wherein the acid cleaning liquid is a hydrochloric acid cleaning liquid.   The acid cleaning method according to claim 7 or 8, wherein the acid cleaning liquid is at least one organic acid cleaning liquid selected from citric acid, formic acid, glycolic acid, or malonic acid.   The acid cleaning method according to any one of claims 7 to 10, wherein the alloy steel is an alloy steel containing 0.3 to 10 wt% in total of Si, Mn and Cr as alloy elements.