JP3472542B2 - Pickling method for stainless steel - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel wastewater, a nitric acid wastewater, a hydrogen fluoride water wastewater and a nitric hydrofluoric acid wastewater used for etching cleaning of electronic parts such as semiconductors. We propose a method for pickling stainless steel that can be effectively reused as a pickling solution. 2. Description of the Related Art Since stainless steel is required to have not only functions such as corrosion resistance and heat resistance, but also beautiful surface (gloss, whiteness, etc.), the production process is generally carried out on stainless steel surface. The quality is ensured by performing the descaling process (descaling process). This scale is an alloy component in steel such as Cr or Fe, which is oxidized in the process of hot rolling or annealing and is formed on the steel surface as an oxide, and has a thickness of several μm to several tens μm. is there. The scale thus produced not only reduces the gloss and the like of the steel surface, but also impairs the corrosion resistance and workability. Therefore, descaling is intended to eliminate these adverse effects. However, since the scale layer formed on the surface of stainless steel is dense and has low reactivity with acid, it is difficult to perform descaling treatment with a common acid such as hydrochloric acid or sulfuric acid applied to carbon steel or the like. is there. Therefore, in the descaling treatment of stainless steel, as a pretreatment for pickling, preliminary removal of scale by blasting, grinder, mechanical brush, bending, tension leveler, crack introduction into the scale layer by skin pass, etc., salt bath
(Molten alkali salt) In general, a Cr-based oxide is modified by immersion treatment or neutral salt electrolysis. Then, following these pretreatments, an acid washing treatment is performed using an acid such as sulfuric acid or nitric hydrofluoric acid (a mixed solution of hydrogen fluoride and nitric acid). In addition, this pickling may play a role as a passivation treatment of the steel surface in addition to a role as a descaling treatment. Among the pickling solutions, nitric hydrofluoric acid has the strongest pickling ability and is widely used because it provides a beautiful surface skin in a short time. In the process of manufacturing electronic parts (hereinafter simply referred to as “electronic parts”) such as silicon wafer semiconductors, quartz parts for liquid crystal, and quartz tubes for baking semiconductors, nitric acid, Hydrogen fluoride water, nitric hydrofluoric acid and the like are used. Therefore, a large amount of nitric acid waste liquid, hydrogen fluoride water waste liquid, and nitric hydrofluoric acid waste liquid are discharged in the process of etching and cleaning electronic components. Moreover, the concentrations of nitric acid and hydrogen fluoride in these waste liquids are relatively high. Therefore, if the waste liquid generated in the electronic component manufacturing process can be used as a pickling solution for descaling stainless steel, both benefits are large and the industrial value is considered to be extremely large. [0005] However, there has been an attempt to use such waste liquid used for etching and cleaning in the manufacturing process of electronic parts as a pickling liquid for stainless steel for descaling. However, there is nothing. In view of the above situation, the present invention provides a nitric acid waste liquid, a hydrogen fluoride water waste liquid, and a nitric hydrofluoric acid waste liquid used for etching and cleaning of electronic components (hereinafter, these are collectively referred to as “waste liquid”).
To be reused as a pickling solution for stainless steel. Therefore, the present inventors have investigated and studied the suitability of these waste liquids used for etching and cleaning of electronic components as a pickling liquid of stainless steel. . As a result, when these waste liquids are used as the pickling liquid for stainless steel, the same good surface quality as the conventional pickling liquid may be obtained.However, depending on the lot of the waste liquid, the surface of the steel after the pickling may be removed. In some cases, surface defects referred to as grain boundary erosion or pits (porous defects) occurred, and it was found that the surface quality of the stainless steel varied greatly. Therefore, as a result of further investigating the causes of such variations, it was found that the contents of Si, B, P, and Cl contained in the waste liquid had an extremely large effect on the surface quality of stainless steel. Completed the invention. [0007] The present invention has been completed based on such knowledge, and the gist of the present invention is to convert a nitric acid waste liquid and / or a hydrogen fluoride water waste liquid used for etching and / or cleaning of electronic parts into stainless steel. A method for pickling stainless steel used as a pickling solution, wherein the pickling solution has a nitric acid concentration of 50 g / l or more and / or a hydrogen fluoride concentration of 10 g / l or more and Si, B, P, C
A method for pickling stainless steel, characterized in that the content of l is adjusted to be 1000 mg / liter or less. [0008] Embodiments of the present invention will be described below. Electronic components contain Si, Ge, II-VI compounds and the like.
1, B, P, etc. are also included. Therefore, when these electronic components are etched or washed with nitric acid, hydrogen fluoride water, or nitric hydrofluoric acid, Si, B, P, and Cl are inevitably mixed into the waste liquid. For example, when etching a silicon wafer, Si is HNO _{3
H 2} SiO _2, and this SiO ₂ is the HF by
It becomes SiF ₆ and is etched. In the case of acid cleaning of electronic components, Si and SiO ₂ are mixed in the waste liquid. In this example, Si is mixed into the waste liquid, but B, P, Cl and the like are also mixed into the waste liquid. When the content of Si, B, P, and Cl in the waste liquid is small, even if the stainless steel is pickled using the waste liquid generated in the electronic component manufacturing process, the surface quality of the stainless steel can be improved. It will be normal without lowering. On the other hand, when stainless steel is pickled using a pickling solution containing Si, B, P and Cl contents higher than a certain limit contained in the waste liquid, grain boundary erosion and pits are formed on the stainless steel surface. The named defects occur. Next, a description will be given of an experiment serving as a basis for determining the contents of Si, B, P, and Cl in a waste liquid used for etching and cleaning of electronic components. For pickling of stainless steel, nitric acid concentration is usually 50 g / l or more (preferably 50 to 150 g / l), and hydrogen fluoride concentration is 10 g / l or more (preferably 10 to 75 g).
/ Liter) of hydrogen fluoride water alone or as a mixed acid. Therefore, stainless steel pickling was performed by replacing these pickling solutions of single or mixed acids with waste solutions adjusted to the same concentration. As a result, pits or pits may be formed on the surface of the stainless steel when the content of even one component of Si, B, P and Cl in the pickling solution exceeds 1000 mg / liter, regardless of whether it is a single or mixed acid pickling solution. In addition, a decrease in gloss due to grain boundary erosion occurred. On the other hand, all of these ingredients are 1000 mg
It was found that when the content was not more than 1 / liter, the same surface quality as stainless steel obtained by treating with a conventional pickling solution could be obtained. From the above experimental facts, in using the waste liquid used for etching and cleaning of electronic components for pickling stainless steel, Si contained in the waste liquid,
It is concluded that the content of B, P, and Cl needs to be 1000 mg / liter or less. Further, the acid concentration of the pickling solution is as follows:
g / l or more (preferably 50 to 150 g / l) of nitric acid, hydrogen fluoride concentration: 10 g / l or more (preferably 10 to 75 g / l) of hydrogen fluoride water alone or as a mixed acid. I do. In other words, the nitric acid concentration is less than 50 g / l and the hydrogen fluoride concentration is less than 10 g / l.
(Gloss, whiteness) cannot be expected. That is, if the concentration is lower than these, descaling of the surface of the stainless steel is not sufficiently performed, and there is no effect of pickling. High concentrations of nitric acid: more than 150 g / liter and hydrogen fluoride: more than 75 g / liter are not preferred because descaling is performed more than necessary and the yield of the product tends to decrease. According to the present invention, when waste liquid used for etching and cleaning of electronic parts is used for pickling stainless steel,
A specific implementation method will be described. The content of the impurity components Si, B, P, and Cl in the waste liquid is 10
If it is not more than 00 mg / liter, only the concentration of the acid may be adjusted. However, as described above, since the contents of Si, B, P, and Cl contained in a normal waste liquid are considerably high, the concentration of these components is adjusted when using this for pickling stainless steel. It is necessary to do. A method for adjusting the concentration will be described below. (1) At least two of nitric acid waste liquid, hydrogen fluoride water waste liquid, nitric hydrofluoric acid waste liquid, unused nitric acid, and unused hydrogen fluoride water
Mix the two. (Mixing of nitric acid waste liquid and hydrogen fluoride water waste liquid, mixing of nitric acid waste liquid and / or hydrogen fluoride water waste liquid with unused nitric acid and / or unused hydrogen fluoride water, etc.) Hydrogen hydride aqueous solution and nitric hydrofluoric acid waste solution are subjected to treatment such as distillation and coprecipitation to remove impurities. EXAMPLES Nitric acid hydrofluoric acid waste liquids (A to E) having the chemical compositions shown in Table 1 and containing nitric acid (reagent grade), hydrogen fluoride water (reagent grade), and semiconductor etching processes Was mixed at various ratios as a stock solution for mixing, or the solution composition was adjusted by dilution with water to obtain a pickling solution. SUS304 (18% Cr-8% Ni,
(Hot rolled sheet was shot-blasted and washed twice with sulfuric acid.)
, SUS430 (17% Cr, hot-rolled sheet which was shot-blasted and pickled twice with sulfuric acid) was pickled, the amount of pickling loss was measured, and the surface quality after pickling was observed by SEM. Reference Example 1 Nitric acid (special grade reagent) and aqueous hydrogen fluoride (special grade reagent) were mixed to adjust nitric acid concentration to 115 g / l and hydrogen fluoride concentration to 22 g / l to prepare nitric hydrofluoric acid. . After SUS304 was washed twice with sulfuric acid, it was washed with the above-mentioned nitric hydrofluoric acid pickling solution. (Reference Example 2) SUS430 was pickled in the same manner as in Reference Example 1. (Invention Example 1) A nitric hydrofluoric acid waste liquid (A) and a nitric hydrofluoric acid waste liquid (B) are mixed with nitric acid (reagent grade) and hydrogen fluoride water (reagent grade), diluted with water, and pickled. The composition of the liquid was adjusted. Using this pickling solution, as in Reference Example 1, SUS
304 was pickled. (Invention Example 2) Nitric hydrofluoric acid waste liquid (C) and nitric hydrofluoric acid waste liquid (D) were mixed with nitric acid (special grade reagent) and hydrogen fluoride water (special grade reagent),
The composition of the pickling liquid was adjusted by dilution with water. Using this pickling solution, SUS430 was pickled in the same manner as in Reference Example 1. (Invention Examples 3 to 5) Pickling solutions of nitric hydrofluoric acid having different nitric acid concentrations were prepared using the stock solutions A, B, N and F shown in Table 1,
After S304 was washed with sulfuric acid twice, it was pickled with the above nitric hydrofluoric acid. As a result, the pickling loss was constant irrespective of the nitric acid concentration, and as a result of surface analysis, it was confirmed that a Cr passivation film was formed. Comparative Example 1 The nitric hydrofluoric acid waste liquid (C) was mixed with nitric acid (special grade reagent) and aqueous hydrogen fluoride (special grade reagent), and diluted with water to adjust the composition of the pickling solution. Using this pickling solution, SUS430 was pickled in the same manner as in Reference Example 1. (Comparative Example 2) The nitric hydrofluoric acid waste liquid (D) was mixed with nitric acid (special grade reagent) and hydrogen fluoride water (special grade reagent), and diluted with water to adjust the composition of the pickling liquid. Using this pickling solution, SUS430 was pickled in the same manner as in Reference Example 1. (Comparative Example 3) The nitric hydrofluoric acid waste liquid (E) was mixed with nitric acid (special grade reagent) and hydrogen fluoride water (special grade reagent), and diluted with water to adjust the composition of the pickling liquid. Using this pickling solution, SUS430 was pickled in the same manner as in Reference Example 1. Table 2 shows the chemical composition of each pickling solution mixed and adjusted by the above method, the amount of pickling loss obtained by pickling using these pickling solutions, and the surface condition of the stainless steel after pickling. Shown together. In addition, Si in the stock solution for mixing and the pickling solution,
The contents of B and P were measured by IPC emission spectrometry, and the content of Cl was measured by turbidimetry (absorptiometry). The content of hydrogen fluoride was measured by a lanthanum fluoride potentiometric titration method. The content of nitric acid was determined by calculating the total acid content by neutralization titration and subtracting the content of hydrogen fluoride. Table 2
From the above, it is apparent that the invention example in which the contents of Si, B, P, and Cl in the pickling solution are adjusted to a predetermined range exhibits the same pickling performance as the reference example in which no waste liquid for manufacturing electronic components is used. It is. [Table 1] [Table 2] As described above, according to the present invention,
Waste liquid used in the manufacture of electronic components such as semiconductors can be effectively used as a pickling solution for stainless steel. Therefore, the present invention greatly contributes to simplification of a waste acid treatment facility in a factory for manufacturing electronic components, reduction of the manufacturing cost of stainless steel, and the like.

Continuing from the front page (72) Inventor Tomohiro Suginaka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corp. Inside the Chiba Works (72) Inventor Shinobu Amano 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corp. Inside Chiba Works (72) Inventor Izumi Nonaka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Kawasaki Steel Corporation Inside Chiba Works (72) Inventor Masashi Fujiwara 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-2002-115087 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23G 1/08 B08B 3/08

Claims (1)

(57) [Claim 1] Pickling of stainless steel using nitric acid waste liquid and / or hydrogen fluoride aqueous waste liquid used for etching and / or cleaning of electronic parts as a pickling liquid for stainless steel. The method according to claim 1, wherein the pickling solution has a nitric acid concentration of 50 g / L or more and / or a hydrogen fluoride concentration of 10 g / L or more and a content of Si, B, P, and Cl of 1,000 m or more.
A method for pickling stainless steel, wherein the method is adjusted to be not more than g / liter.