JPH04501139A - Pickling method using a pickling bath for metal products containing titanium or at least one element chemically similar to titanium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] name of invention Pickling of metal products containing titanium or at least one element chemically similar to titanium Pickling method using a bath The present invention uses titanium or an element chemically similar to titanium. The present invention relates to a method for pickling a metal product containing at least one metal product in an acid bath.

In the metallurgical field, metal products or alloys that have undergone forging or heat treatment during the manufacturing process. It is known that the product is covered with alumine. most In order to improve the surface quality of the finished product, all rust layers must be removed by pickling. need to be removed.

In the known pickling treatment, pickling is composed of nitric acid, HNO, and hydrofluoric acid, HF. in a pickling bath with a ratio of 6 to 16% nitric acid and 1 to 5% hydrofluoric acid per 11 Soak the final product. The operating temperature of the pickling bath in this case is 40°C to 60°C.

One of the most commonly used pickling baths for pickling titanium is nitric acid-based. However, nitric acid generates extremely toxic NO3 vapor, and the waste liquid contains nitrogen compounds (nitrous oxide). nitrates and nitrates). The maximum content of nitrates allowed by law is However, nitrite is a toxic substance, nitrosamine (nitosan + 1ne). ), its maximum content is much lower.

It is composed of a mixture of halogen acids containing hydrochloric acid HCI and hydrofluoric acid HF as the main components. Methods for pickling titanium-based metallurgical products using baths are also known.

The disadvantage of this method is that during dissolution, titanium is reduced to its valence and forms a volatile compound. At the point.

For example, when titanium is dissolved in hydrochloric acid, it is converted to TiC1s, and this TiC1- is 8 Sublimes below 0℃. This TiCls is converted into TiCl before sublimation according to the reaction formula below. Decomposed into 4+TiC1i: 2 TiC1s-TiCl4+TiC1i (I ) TIC14 is particularly volatile, and its vapor pressure is 42 m/Hg at 50°C. .

The object of the present invention is to add an oxidant to a pickling bath that does not have the drawbacks of the above-mentioned pickling methods. metallurgical product containing at least one titanium or chemically similar element to titanium It is an object of the present invention to provide a method for pickling products in an acidic medium. In order to increase the cinetique, (1) Titanium or at least one chemically similar to titanium contained in the product to be pickled; At least one peroxygene of similar elements ) to make the metal a higher valence ion, and (2) redox (redox). b) controlling the formation of said peracid compound by measuring the potential; (3) Oxidizing agent so that the redox potential is below the badge version potential of the metal product. The point is to limit the amount of

The fact underlying this method is that the metal's oxygen species have become ions with higher valences. Sometimes more aggressive than the metal itself and its lower valence oxides. It means being aggressive. Ions with higher valences are especially titanates, Ions of noinadate, zirconate, niobate, tantalate, uranate means something like

The above pickling bath basically consists of hydrofluoric acid, sulfuric acid, hydrochloric acid, phosphoric acid and formic acid. Preferably, the bath contains an acid selected from the group consisting of: Using other washable acids or mixtures of mineral acids such as HF-H, SO, You can also do it.

To initiate the pickling reaction, a peroxide compound of at least one metal is formed. An oxidizing agent with strong oxidizing ability is introduced into the pickling bath.

Titanium or elements chemically similar to titanium form monoperoxide compounds with oxidizing agents. It is worth noting that. Depending on the degree of oxidation achieved, the following A compound is obtained = (where M is Ti or a chemically similar element of Ti) The compounds constitute persels, which are particularly strong oxidizing substances.

The above oxidizing agents can be hydrogen peroxide, urea peroxide or gases such as ozone and oxygen. Preferably.

Hydrogen peroxide is introduced directly into the pickling bath in an amount of up to 0.5% by weight. Additionally, acidic It may be introduced in the form of a persalt or peracid, which decomposes in the medium to produce hydrogen peroxide. Can also be done. Urea peroxide G can be used in an amount of 11.2% by weight or less.

The invention will be more easily understood from the following description.

The method according to the invention comprises titanium or at least one chemically similar element of titanium, in particular titanium. metals including vanadium, zirconium, niobium, tantalum and uranium; relates to a method for pickling alloy products in a pickling bath.

The pickling reaction mechanism is almost the same for each of the above metals and their alloys. Therefore, I will explain in detail how to pickle titanium using an example.

The basic pickling bath is a fluorinated pickling bath with a concentration of hydrofluoric acid ranging from 0.2 to 10% by weight. A bath of hydrogen acid, preferably a bath of chemically similar titanium contained in the pickled product. Other acids, such as sulfuric acid, can be used as long as they contain the element in the form of a peracid. You can also use

In the example of pickling titanium, titanium oxide is attacked by hydrofluoric acid by the following reaction: Laboratory tests have confirmed that: 2Ti+6HF → 2'riF'3 +3H2↑ (II) Excess HF exists Titanium trifluoride is then converted to tetrafluoride 7iF4.

In the method of the invention, ions of higher valence are used to increase the rate of the pickling reaction. forming at least one metal oxide having a composition of at least one metal oxide; In the case of pickling titanium, Vertitane, a titanium peroxide compound that is particularly aggressive towards titanium and its oxides. form a grid.

This vertitanate is produced by adding water peroxide to titanium fluoride, for example, by the following reaction. It can be made by interacting with the elements = TI” + HJ* + 2H*0 → Ti O4"-+ 6H" (III) 2 TiO4"-+ Ti + 16H+→ 3Ti'◆+8H,0(IV) In the reaction (IV), there is no excess H'', and H30 is formed, thereby allowing H4 to enter the crystal lattice network of the pickled metal or alloy. The effect is reduced, resulting in less brittleness of the product in the pickling bath.

Vertitanate can be obtained through the action of urea peroxide, which decomposes to produce hydrogen peroxide. Can also be done. Urea peroxide is a solid, which makes it easier to transport.

Additionally, vertitanate can be formed by injecting heozone into the bath. You can also do it. The reaction for producing vertitanate in this case is as follows: Ti" + Os + HtO → Ti4"-+ H2" (V)2Ti04"- + Ti + 16H" → 3Ti" + 8HiO (VI) Oxygen instead of ozone You can also use

It is known that when persalts are introduced into acidic media, they decompose to form hydrogen peroxide. ing. Persalts that can be used include permanganates, persulfates, and vertitanes, among others. Examples include berbanate, bervanadate, berborate, and the like.

Additionally, peracid compounds that decompose into HaOx in acidic media can also be used. . Examples of peracid compounds include perboric acid and titanium peroxide, which are used in other industrial fields. Mention may be made of tan, peracetic acid and persulfuric acid.

The formation of T1042″ is caused by the redox potential of the pickling bath. controlled by measuring the ydo-reduct 1on).

This oxidation-reduction potential (RBIIOX potential) is determined by A corrosive electrode (e.g. platinum electrode) and a reference electrode (e.g. Ag/AgCl or saturated Calomel electrode).

This measured value is a value that characterizes the oxidizing ability of the pickling bath. Also, based on this measurement The pickling bath is reconditioned by introducing the above-mentioned compounds to maintain the pickling bath at the desired oxidation capacity. can be adjusted. In order to pickle titanium or titanium compounds, the above oxidation The reduction potential must be within the following range: (+150.-350) mV/Ag/AgC1 In the method of the present invention, the main oxidant is titanium. peroxide compound, preferably a single acid, containing an element chemically similar to titanium or titanium. Using a standard bath containing only titanium, titanium and its alloys, which are chemically similar to titanium, It improves the pickling efficiency of similar elements and their alloys.

In one example of pickling titanium using the method of the invention, the weight loss of the flat product was 4. 0 to 80 g/m''.The obtained surface condition was obtained using the nitric acid/hydrogen fluoride method. Comparable to those prepared in this way, and does not have an excessive pickling bath effect. Surface treated with hydrogen peroxide becomes white and has an aesthetically pleasing appearance.

An important aspect of the method of the invention is that the oxidizing agent is It lies in the fact that it is “created in situ”, that is, in the system.

The pickling reaction is carried out by titanium peroxide or peroxides of elements chemically similar to titanium. occurs, so the consumption of hydrofluoric acid is reduced.

The method of the invention does not cause air pollution and the wastewater can be treated and recycled, so pickling The service life of the bath can be extended.

Peracid compounds (Vertitanate, Verzirconate, Vertanthalate, Bernio) H, which has no ecological problems in the formation of bate, beluranate, belbanadate). Just add O□.

This H, O□ is decomposed into H, O and 02, which are favorable for living things.

Therefore, the method of the present invention can reduce the release of harmful substances into the atmosphere and into wastewater, and furthermore, You can also eliminate these altogether.

This waste water and the used pickling bath can be treated in accordance with the regulations of industrialized countries. example For example, treatment with lime emulsion can precipitate metal hydroxides and remove harmful anions. It is possible to prevent on from flowing out. In contrast, when using nitrates All of these dissolve in water. The method of the present invention is an ecological method. .

In the method of the present invention, an oxidizing agent bath can be used without generating excess hydrogen, so a reducing agent can be used. The diffusion of hydrogen into the metal network of the product to be pickled, which tends to occur in baths, is reduced, and the product after pickling is becomes less brittle.

international search report -Poichi+^--IN, PCT/FR90100564 International Search Report FR9000564

Claims (1)

[Claims] 1. At least one titanium or chemically similar element to titanium is added to an acid bath containing an oxidizing agent. In the method of pickling in an acid bath by introducing a metal product or an alloy product containing To increase the reaction rate of pickling, (1) Titanium or at least one chemically similar to titanium contained in the product to be pickled; The formation of at least one peroxide compound of similar elements to bind metals to higher valence atoms. (2) The amount of peracid compound formed by measuring the redox potential control, (3) Oxidizing agent so that the redox potential is below the passivation potential of the metal product. limit the amount of A method characterized by: 2. From the group in which the acid bath consists of hydrofluoric acid, sulfuric acid, hydrochloric acid, phosphoric acid, and formic acid 2. The method of claim 1, wherein the bath comprises one selected acid. 3. The method according to claim 1 or 2, wherein the oxidizing agent is oxygen gas or ozone gas. 4. 4. A method according to claims 1 to 3, wherein the oxidizing agent is hydrogen peroxide or urea peroxide. 5. The above redox potential during pickling of titanium or titanium compound is (+150, -3 50) The method of claim 1 in the range of mV/Ag/AgCl. 6. Claim 4, wherein the amount of hydrogen peroxide introduced into the acid bath is 0.5% by weight or less. How to put it on. 7. Claim 4, wherein the amount of urea peroxide introduced into the acid bath is 1.2% by weight or less. the method of. 8. 3. The method according to claim 1 or 2, wherein the oxidizing agent is a peroxide salt. 9. If the peroxide salt contains titanium or a small amount chemically similar to titanium in the pickled product, 9. The method according to claim 8, wherein the peroxide salt has a strong oxidizing ability of at least one element. 10. The method according to claim 1 or 2, wherein the oxidizing agent is a peracid compound. 11. The peroxide compound is chemically similar to titanium or titanium contained in the pickled product. 11. The method according to claim 10, wherein the peroxide compound is a peroxide compound of at least one element. 12. Elements chemically similar to titanium or vanadium, zirconium, niobium, tan 12. The method according to any one of claims 1 to 11, wherein the metal is tal or uranium.