CS257878B1 - A solution for distinguishing steel with different chromium content - Google Patents

Abstract

The purpose of the solution is to quickly distinguish steel with different chromium contents. The steel surface is subjected to an aqueous solution of copper, nitrate, selenium, sulfate and possibly chloride ions. The solution contains 3.5 to 4.5 wt. % selenium dioxide, 4.5 to 6 wt. % copper sulfate pentahydrate, 3 to 32 wt. % nitric acid, possibly 0.1 to 5 wt. % hydrochloric acid and the rest water. The area of application is mainly in mechanical engineering and sorting of metal waste

Description

The invention relates to a solution for distinguishing steels with different chromium contents. It is intended for the non-destructive distinction of those types of steels whose chromium content differs by at least 5% by weight.

Chromium content is a decisive feature of many steels and its knowledge is often sufficient to distinguish a known choice of possible types. Normally, destructive testing methods are known in which a part of the material or partially destructive analysis is separated in which the content of several elements is usually ensured by means of an optical emission spectrometer. Here the material is damaged up to a depth of 0.2 mm and on an area of 5 mm. Changing the material of a certain machine part to a material of lower quality, that is, with a lower chromium content, can be critical to the life and reliability of the machine. Therefore, distinguishing steel according to the chromium content is a frequent inspection task. Also, in the recovery of scrap metal as a secondary raw material, knowledge of chromium content is often a key criterion. All previous methods require laboratory processing, demanding instrumentation and qualified personnel.

These drawbacks are overcome by the solution for distinguishing steels with different chromium contents according to the invention. It consists of 3.5 to 5.5 wt. selenium dioxide,

4.5 to 6 wt. copper sulfate pentahydrate, 3 to 32% nitric acid and the rest water. According to another feature, the solution may contain 0.1 to 5 wt. hydrochloric acid.

The surface of the steel to be tested is treated with an aqueous solution of copper, nitrate, silicon, optionally chloride and sulfate ions.

The basic advantage of the solution according to the invention is that it enables a fast, reliable test outside the laboratory to be carried out quickly without extremely qualified personnel. Up to 1,000 parts per hour can be expected. The resolution limit can be controlled by the nitric and hydrochloric acid content of the solution. Intensity and color independent! on the chromium content below the resolution threshold.

It has been found that the limit of chromium content resolution is not significantly influenced by the simultaneous presence of other alloying elements commonly used in conventional steels containing astonishment. The influence of carbon, manganese, silicon, phosphorus, sulfur, nickel, copper, molybdenum, cobalt, zirconium, titanium, nubium was experimentally excluded. The effect of vanadium and tungsten will appear as chromium with one hundredth of the total content of these elements.

The table below shows the values of the individual components of the solutions used to identify steel with a chromium content lower than that indicated in the table (the surface trace turns black).

black steel Composition of the respective solution containing

Cr less than wt. % nitric acid % hydrochloric acid oxide % selenium in% wt. % copper sulfate pentahydrate in wt. 4 3 to 5 - 4 4,5 8 25 to 32 - 4 4,5 13 3 to 5 3 4 4,5 17 5 to 10 5 4 4,5

For the 4% wt. of chromium is 3 to 5 wt. % of nitric acid without hydrochloric acid, for the limit of 8% by weight % chromium is 25 to 32 wt. % of nitric acid without hydrochloric acid, for the 13% wt. of chromium is 3 to 5 wt. % of nitric acid and 3% by weight of hydrochloric acid; chromium is 5 to 10 wt. % nitric acid and 5 wt. hydrochloric acid. All solution variants contain 4 wt. % selenium dioxide and 4.5 wt. copper (II) sulfate pentahydrate; the rest is water. Pencil markers can advantageously be used to apply the solution. Since the surface of the higher chromium component is not damaged during the test, no further surface treatments of the product are required for a positive inspection result. The surface of the lower chromium component is impacted to a depth of several micrometers. The rate of reaction of the surface with the test solution and hence the rate of visual resolution is several seconds.

The solution according to the invention is described in more detail below with reference to a specific embodiment.

Example

To differentiate steel rivets with less than 1 wt. and steels with a chromium content exceeding 10% by weight. a solution of the following composition was prepared: one part by weight of elemental selenium was oxidatively dissolved in two parts by weight of nitric acid of specific weight □

Further, two parts by weight of copper sulfate pentahydrate were added and dissolved in thirty parts by weight of water. The solution was filled into a pencil-top recorder. As a result, the components were described by a slight pressure of about 5 mm. In steel with a chromium content of less than 1% by weight. the footprint turned black within one second, for steel with a chromium content greater than 10% by weight. the surface remained unchanged.

Claims (2)

CLAIMS 1. A solution for distinguishing steels with different chromium contents, characterized in that it contains 3.5 to 2.0 4.5 wt. % selenium dioxide, 4.5 to 6 wt. % copper sulfate pentahydrate, 3 to 32 wt. nitric acid and the rest water. 2. A solution according to claim 1 comprising 0.1 to 5 wt. hydrochloric acid.