DE1621556B1 - Process for cleaning, in particular for descaling metal surfaces in molten salts - Google Patents

Description

3 4

are coated. The proportion of sodium chloride containing hydrogen compounds that z. B. at the

acts that the molten salt a very low viscous treatment of titanium lead to difficulties

The metal to be cleaned is about 30 seconds

half of 500 ° C or such from 350 to 450 ° C immersed in the melt, then washed and

can be applied. 5 of the known pickling treatment in dilute acids

The salt mixture contains no carbonate and no subject.

Claims (2)

1 2 480 ° C and the duration of treatment. 30 seconds. Claims: ■ After quenching in water and pickling in dilute acid, it was found that the entire surface 1. Methods for cleaning, in particular for the surface layer of glass and scale through this Descaling of metal surfaces in salt- 5 single treatment was removed. melt, the alkali hydroxide, chloride and
-nitrate, characterized in that a mixture of about 12 weight- Example 2
percent sodium nitrate, about 10 percent by weight Sodium chloride, about 63 percent by weight Na- io. trium hydroxide and about 15 percent by weight pieces of titanium immersed in an annealing process Potassium hydroxide is used. . 'at 1200 ° C. The one on the upper 2. The method according to claim 1, characterized in that the scale layer present on the surface is also indicated in that the molten salt is kept at a temperature of between 350 and 450 ° C on one of this material by a single treatment without the material taking up hydrogen,
will. It has now been found that those in the above Cases occurring disadvantages of the known salt mixtures then do not exist when a salt mixture of a very specific composition setting is used. According to the invention, the mixture consists of about 12 percent by weight sodium nitrate, about 10 percent by weight sodium chloride, It is known that metal surfaces, in particular about 63 percent by weight sodium hydroxide and, for example, of steels, can be cleaned or descaled in this way, 15 percent by weight potassium hydroxide,
that they are immersed in a molten salt composed of a mixture. US Pat. No. 2,738,293, salts of alkali metal hydroxide and nitrate are melted at a temperature for cleaning metal surfaces of about 400 to 500.degree. After becoming alkali, which consists of sodium nitrate, sodium hydroxide oxidizing salt melt, the tinder hydroxide and potassium hydroxide will be made. The loosened up, so that the subsequent pickling with the ratio of potassium to sodium hydroxide is short pickling times and with a very low metal 30 here about 1:10, while the ratio of level loss and acid consumption is sufficient. joined to hydroxide is about 1: 1. Additionally owns The known salt mixtures have proven themselves in many cases, the mixture according to the invention, however, difficulties arise in certain approximately 10 percent by weight of sodium chloride, one proportion of cases. This applies e.g. B. for the. Reini _T which is essential to reduce the viscosity of the salt mixture supply of the surfaces of workpieces made of rust 35 and the use of relatively low-free steel, z. B. of pipes, to allow rigeren temperatures during their manufacture. The inventive extrusion or drawing process is used, according to the combination enables an ignition where glass is used as a lubricant. In this case, it is possible to achieve a value that is at least as good as a firmly bonded surface layer, which in the known method, with the lower temperature essentially consisting of glass. This layer can be used 40 temperatures and is made possible by the known molten salt only through a low viscosity, which can be removed in the multiple immersion treatment. The same sludge passing into the melt, difficulties arise in the removal of the easily removed sludge, at the same time only a ge-scale layer of titanium and titanium alloys, the small amount of salt mixture on the treated works have been subjected to a heat treatment. 45 pieces get stuck, so that the salt bath has to be refilled at relatively high temperatures only at relatively long intervals. turn around; Furthermore, the known salt mixtures have the disadvantage that they have a relatively large drive for descaling, so that it is difficult to obtain a mixture of nitrate and hydroxide is used, the treatment going into the melt 50 to which a certain amount of chloride is added.
Remove mud. The composition described was carried out by In the case of certain steel alloys, to increase the composition claimed according to the invention the temperature resistance with nickel, manganese, molyb- improved. It has been shown that only with one Danish or tungsten are alloyed, the specific dimensioning of the proportions shows an optimal one Use of the known salt mixtures that on 55 "descaling effect" occurs, in particular more oxides are formed on the surface than from the combination of potassium hydroxide with sodium der Molten salt can be removed. hydroxide has a special effect. The mixture of the invention is very effective and reliable in use and especially not Example 1 60 corrosive for the system used, especially the bath tank. The weight loss A batch of glass-covered tubes made from potassium hydroxide to sodium hydroxide ratio stainless steel, which in an extrusion process of about 1 to 4 causes the molten salt at A large number of metals are very effective and are melted in a melt dips, which consists of 12 percent by weight sodium nitrate, 65 in particular a descaling of titanium and 10 percent by weight sodium chloride, 15 percent by weight titanium alloys is possible. With such a percentage Potassium hydroxide and 63 weight percent composition can also be used on metal surfaces Sodium hydroxide. The temperature was clean that with a vitreous lubricant