JPS59118890A - Aqueous solution of descaling agent for replenishing oxidizing molten salt of alkali - Google Patents

Abstract

PURPOSE:To enable use of a liquid alkali and to reduce cost by using an aq. soln. consisting of specific concns. of alkali metal hydroxide and alkali metal nitrate and preparing the same into the soln. having the solute concn. in a specific range. CONSTITUTION:An aq. soln. of descaling agent used for replenishing oxidizing molten salt of alkali for removing metallic oxide scale is formed of a uniform aq. soln. consisting, by wt%, of 6-41.4 alkali metal hydroxide, 2.5-20 alkali metal nitrate, and the balance water and having 10-56.9 solute concn. Otherwise, said soln. is formed of a uniform aq. soln. consisting of 5.8-32.8 alkali metal hydroxide, 2.2-19.1 alkali metal nitrate, 0.4-4 alkali metal chloride and the balance water and having 10-50.3 solute concn. Sodium, more particularly a commercially marketed liquid sodium hydroxide having about 50% concn. is used as the alkali metal in terms of cost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a descaling agent water bath used for replenishing oxidizing alkali molten salt for descaling metal oxide scale.

Methods for removing surface scales that occur during heat treatment of various alloys such as stainless steel, titanium, heat-resistant steel, and super alloys are well known, and the composition, performance, etc. are also covered by U.S. Patent A2,458,661 and Japanese Patent Publication No. 45-1800.
It is described in detail in Publication No. 1, etc. Said Special Public Service 1977-
Publication No. 18001 states that the inclusion of potassium hydroxide has the effect of improving scale removal performance and lowering the viscosity of the salt bath.

Normally, this molten salt is kept at a temperature of 100°C or higher, reaching as high as 500°C, and is virtually anhydrous, so if the salt to be replenished contains water, the moment it comes into contact with the high-temperature molten salt, The rapid volumetric expansion caused by water evaporation caused a steam explosion, which was extremely dangerous, so it had to be replenished in an absolutely anhydrous state. Therefore, the preparation of the salt used for this supplementation is either by mixing the ingredients that make up this salt, or by
Alternatively, a #I melt-mixed salt in the form of flakes or other solid forms was used. However, since replenishment is limited to solid materials, when workers approach molten salt at high temperatures and replenish it, the molten salt may splatter and cause injury due to the solid state of the replenishing funds. There is a risk.

Furthermore, even when automatic supply is performed, alkali metal hydroxides, such as sodium hydroxide and potassium hydroxide, which are one of the main components of this molten salt, are deliquescent, and if left in the air, water, There were various problems such as absorbing carbon dioxide gas, turning it into a semi-liquid state or changing its quality, and that it was difficult to automatically feed it with a hopper or feeder.

On the other hand, U.S. Pat. In applying the oxidizing alkali molten salt to be used, conditions such as the specific composition, concentration, temperature, etc. of the aqueous solution to be replenished are not disclosed at all.

The present invention relates to the above-mentioned American J'l' JK 4, 113
, 511 is applied to the replenishment of oxidizing alkali 1 volume molten salt used for removing scale from the surface of metals, the applicable composition and optimal composition of the aqueous solution of the salt to be replenished, such as 4 degrees, etc. The purpose is to quantitatively set and provide various conditions.

First, as a result of various tests, studies, and studies, the present inventors have discovered that by replenishing salt in the form of an aqueous solution, automatic supply becomes possible, and in addition to the expected effects of eliminating danger during replenishment work, It was found that the following effects can be obtained.

Alkali metal hydroxides, which are one of the main components of molten salt, such as thorium hydroxide and potassium hydroxide, are produced in a liquid form by bending in a chemical factory, and then undergo a compression process to form a liquid with a concentration of around 50%. Generally, it is commercially available as an alkali, and conventionally the salt to be supplied was required to be anhydrous, so it was further made anhydrous by concentration and used for a long time.

According to the method of the present invention, liquid alkali sold by Tff can be conveniently used and can be used with appropriate modifications.
By omitting the boiling process to make the product anhydrous, the manufacturing cost of raw materials can be reduced. Therefore, an experiment was conducted to find conditions such as the composition and concentration of an aqueous solution of a replenishing descaling agent that can be used for these raw materials and has good descaling properties when mixed with molten salt. : As a result of repeated studies, regarding the formulation of the descaling agent used as the bath material, the formulation ratio of the composition known in U.S. Patent Office 2,458.661 and Japanese Patent Publication No. 18001/1983 was found to be the most excellent in terms of scale removal performance. It turned out that. However, the concentration and temperature must be adjusted to ensure that the composition is replenished at a constant rate, to prevent nozzle clogging when using this aqueous solution for spraying, and to satisfy the conditions for a uniform solution. Therefore, it became necessary to select an appropriate concentration and temperature.

Historically, the most noteworthy feature of the present invention is that metal products can be manufactured by using a molten salt in which this descaling agent water M solution is repeatedly replenished and a conventional molten salt containing only anhydrous solid salt. When comparing the descaling performance of , t15 when replenishing and mixing as an aqueous solution is the one that provides excellent descaling performance. This is the result of analyzing and studying molten salt that has been repeatedly replenished with an aqueous descaling agent solution.
Molten salt contains 3 to 5% water, and this water effectively reduces the viscosity of the molten salt, promoting penetration of the molten salt from the surface of the scale to the inside, improving reactivity. I think it depends on what happens. Furthermore, it was found that this water content was hardly affected by the number of times and the amount of replenishment of the aqueous descaling agent solution, and maintained an approximately constant ratio.

For these reasons, all of the above effects can be achieved by using a descaling agent aqueous solution with a concentration range shown below. We can separate.

■ Descaling agent aqueous solution consisting of alkali metal hydroxide and alkali metal nitrate Alkali metal hydroxide 6.0 to 41.4% by weight
Alkali metal nitrate 2.5-20.8% by weight Solute concentration 10.0-56.9% by weight Temperature range (to make a homogeneous solution) 8-65°C Compared to the above alkali metal compounds, the cost is relatively low. For this reason, sodium compounds are usually used.

(2) Descaling agent aqueous solution consisting of alkali metal hydroxide, alkali wire mesh nitrate and alkali metal chloride Alkali metal hydroxide: 5.8-32.2% by weight Alkali metal nitrate: 2.2-19.1% by weight
Alkali metal chloride 0.4 to 4.0 % solute concentration 10.0 to 50.5 % (to make a homogeneous solution) 10 to 65°C For the above alkali metal compounds, comparison Sodium compounds are usually used because of their low cost.

(2) The composition of an aqueous descaling agent solution in which potassium hydroxide is also added to the above composition, which has excellent performance in removing scales from stainless steel, titanium, titanium alloys, etc., is shown below.

Descaling agent aqueous solution consisting of sodium hydroxide, alkali metal nitrate, alkali metal chloride and potassium hydroxide Sodium hydroxide 8.0-38.6 wt% Alkali metal nitrate 0.8-5.8 wt% alkali metal chloride Things 0.5-5.8 Jii
% potassium hydroxide 0.8-7.8 wt% solute a
Potassium hydroxide must coexist with sodium hydroxide as an essential component of the descaling agent aqueous solution at a temperature of 10.1 to 49.4% by weight (to make a homogeneous solution) from 15 to 50 degrees Celsius. As for the remaining alkali metal nitrates and alkali metal chlorides, sodium compounds are usually used because of their relatively low cost.

In the above three types of descaling agent aqueous solutions, if the above-mentioned solute concentration exceeds each upper limit, a uniform solution cannot be obtained within the temperature at which the solute is practically punched. Although it is possible to use solute concentrations below the respective lower limits, it is not economically advantageous because the amount of stool increases.

When storing the descaling agent aqueous solution of the present invention and replenishing it through a pipe or the like, it is necessary to maintain the temperature within the above-mentioned temperature range.

Next, embodiments of this invention will be described.

Example 1 - Test material: 8U85Q4 Cold rolled steel plate (1, 5, 1 thickness) annealing results The above test material was descaled under the following conditions,
Descaling performance was determined by comparing the time required for final pickling.

2) Molten salt composition and conditions ■ Hydroxide) IJum 12.6 kg (mixing ratio 65
%), nitric acid) IJum 2.4 (mixing ratio 12%)
, chloride) IJum 2 to 9 (mixing ratio 10%), potassium hydroxide 5 parts (mixing ratio 15%), total amount 20 kli
Conventional molten salt without supplementing with an aqueous descaling agent solution.

Treatment temperature: 420°C and 450°C ■ To the molten salt prepared at %), 1 kg of sodium chloride (solid mixture ratio 10%), 48% liquid potassium hydroxide 3.1 y (solid mixture ratio 15%),
2.8 kg of water, total solute concentration 47.2%, solution temperature 50
A molten salt obtained by replenishing the replenishing descaling agent aqueous solution of the present invention, which has become a homogeneous solution by maintaining the temperature at ℃, at a rate of 26.517 nin for 6 hours.

Processing temperature: 420°C and 450°C 6) Pickling liquid Pre-pickling: Sulfuric acid 104.9'/1.50°C Final pickling: Nitrofluoric acid HN (J, 58.8F -HF5.4'
/7.22°C Processing order and processing time Salt bath treatment (15 seconds) → Rapid cooling water washing → Sulfuric acid pickling (60 seconds) →
Water washing → Nitrofluoric acid pickling (required time) 5) Descaling results Example 2 1) Test material: 8US450 cold rolled steel plate (0, 7, I thickness) sintered and purified 2) and 5) are the same as Example 1. Same treatment order and treatment time Salt bath treatment (4 seconds) → Rapid cooling water washing → Sulfuric acid pickling (60 seconds) - Water washing → Nitrofluoric acid pickling (required time) 5) Descaling results are shown in Examples 1 and 2. As can be seen, it has been found that the replenishing descaling agent aqueous solution of the present invention shortens the processing time compared to the conventional method and has an extremely excellent descaling effect.

In addition, regarding the descaling agent aqueous solution consisting of alkali metal hydroxide and alkali metal hydroxide indicated by l and the descaling agent aqueous solution consisting of alkali metal hydroxide, alkali metal nitrate and alkali metal chloride indicated by M, Since the descaling performance with the conventional molten salt used in an anhydrous state has been known, replenishment with an aqueous descaling agent solution was limited to case 1 only.

As described above, the present invention eliminates the inconvenience of replenishing the conventional tower molten salt for descaling metal oxides in a solid state.
Not only can it solve all problems such as the danger of supplementary work, but it also has advantages such as lower costs because it can use commercially available liquid alkali as a raw material, and improved descaling effect when mixed with molten salt. This invention can be said to be extremely beneficial to the metal box manufacturing industry because it exhibits the following effects and improves work efficiency by shortening the pickling treatment time.

Agent Patent Attorney Isao Fujimoto Procedural Amendment February 9, 1980 Commissioner of the Patent Office 1. Indication of the case 1981 Patent Application No. 226928 3. Person making the amendment (Relationship with It) Patent application Person 4, Agent Address: 105 Telephone: 05-274-3
4666, Number of inventions increased by amendment 7, Contents of amendment subject to amendment (li) "Composition of" in line 8 of page 10 of the specification is corrected to "composition of molten salt, ie."

(2) Delete "Processing temperature: 420°C and 45.0°C" on page 10, line 10.

(3) "Processing temperature = 420℃ and 4
50℃" is deleted.

(Next to the table listed in the 4th to 8th lines of the 12th edition of the same publication, it is written as follows: ``Example 3 1) Same as Example 1 2) Molten salt composition and conditions (75%)
, sodium nitrate s kp (mixing ratio 25%), a total amount of 20 g, is melt-mixed, i.e., a conventional molten salt without replenishing the descaling agent water bath solution.

■ Add 48% liquid hydroxide to the molten salt prepared in ■) I
Jum 15.6 to 9 (solid mixture ratio 75.0%), sodium nitrate 2.5 kill (solid mixture ratio 25%)
, total solute concentration 55.2%, solution temperature maintained at 50° C. to become a homogeneous solution, replenishment descaling agent water m liquid f:, 26.5′/,. m molten salt obtained by replenishing at a rate of in for 6 hours.

3) and 4) are the same as Example 1 5) Descaling results Example 4 1) are the same as Example 1 2) Molten salt composition and conditions ■ Hydroxylation) IJum 12.8 klil (mixing ratio 64% ), sodium nitrate 6.2):p (mixing ratio 51%), sodium chloride 1kg (mixing ratio 5%)
A molten salt having a composition in which a total amount of 20 kg is melt-mixed, that is, a conventional molten salt without replenishing an aqueous descaling agent solution.

■ To the molten salt prepared in ■, 13.3 kg of 48% liquid sodium hydroxide (solid mixture ratio 64.0%), sodium nitrate 3.1 kg (solid mixture ratio 31%), sodium chloride, sl (solid mixture ratio 5%), 9 parts to 3 parts water.
Obtained by replenishing the replenishing descaling agent aqueous solution of the present invention, which has a total solute concentration of 50.2% and a solution temperature of 64° C. to form a uniform bath solution, at a rate of 26”/min for 6 hours. m
Molten salt.

3), ri are the same as Example 1 5) Descaling results Insert.

(5) On page 12, line 9, "as shown in Examples 1 and 2" is corrected to "as shown in the examples."

(6) “In addition,” from page 12, line 13 to page 13, line 1,
・・・・・・・・・Delete "Totome to".

Claims (1)

[Scope of Claims] (Li) A descaling agent water bath liquid used for replenishing oxidizing alkali IJM molten salt for descaling metal oxide scale, comprising: 6.0 to 41.4 weight of alkali metal hydroxide %, alkali gold nitrate 2.5 to 20.8% by weight, and the remainder water, and the descaling aqueous solution is made into a uniform aqueous solution with a solute concentration of 10.0 to 56.9% by weight. (2) Descaling agent water or liquid used for replenishing oxidizing alkali molten salt for descaling metal oxide scale, comprising: 5.8 to 32.2% by weight of alkali metal hydroxide, and alkali Kanasu nitrate 2.2 to 19.1% by weight,
1. A descaling agent aqueous solution comprising 0.4 to 4.0% by weight of an alkali metal chloride and the balance being water, and having a solute degree of 10.0 to 50.6% by weight. (3) A descaling agent aqueous solution used for replenishing oxidizing alkali molten salt for descaling metal oxide scale, comprising: 8.0 to 38.6% by weight of sodium hydroxide.
, 31% by weight of alkali metal nitrate, 0.5 to 5.8% by weight of alkali metal chloride, 0.8 to 7.8% by weight of potassium hydroxide, and the balance is water, 1. A descaling agent aqueous solution, characterized in that it is a homogeneous aqueous solution having a solute concentration of 10.1 to 49.4% by weight.