DE561160C - Manufacture of items that are exposed to warming during the manufacturing process or in the factory - Google Patents

Description

GERMAN EMPIRE

ISSUED ON OCTOBER 12, 1932

REICH PATENT OFFICE

PATENT LETTERING

CLASS 18 b GROUP

Fried. Krupp Akt.-Ges. in Essen, Ruhr *)

Patented in the German Empire on February 10, 1928

Up to now in the production of nitric acid and other chemical agents used objects made of chemically neutral austenitic chromium-nickel-steel-alloy-S ments have the disadvantage that they are against the z. B. attack occurring at high temperature of acids or salt solutions are no longer resistant if they (e.g. when welding together individual components or in the company) a tempering treatment equivalent to heating to about 600 to 900 ° C. The invention aims for the production of such the '' Objects exposed to chemical agents, which either during the manufacturing process, z. B. during welding, or in the factory are exposed to a tempering treatment equivalent to warming, such austenitic chromium-nickel-steel alloys, z. B. to use those with 18 to 25% chromium and 7 to 12% nickel, which are free from this disadvantage and, moreover, all the advantages of the known chemical neutral austenitic chromium-nickel-steel alloys exhibit. This purpose is achieved according to the invention in that for the manufacture of objects that either in the manufacturing process, e.g. B. welding, or in the company a tempering treatment are exposed to the same heating, known austenitic chromium-nickel-steel alloys with z. B. 18 up to 25 ° / o chromium and 7 to 12 ° / o nickel and a carbon content below 0,07 ° / o be used.

The reason for the surprising fact that the specified steel alloys also have the property (which is very important for technology) that they are insensitive to attack by acids or salt solutions at elevated temperatures is, according to the inventor's findings, to be seen in the fact that the very small amount of carbon (less than 0.07 ⁰ Z ₀ ) in the alloy, after it has been converted into the dissolved form, in any case remains permanently in the dissolved form despite the action of elevated temperature. So you will not even by a subsequent, a tempering treatment equivalent to warming to about 600 to 900 ° C, as z. B. for welding together individual !: components is required, converted into a different form (e.g. carbide form). This is not the case with the chemically neutral austenitic chromium-nickel-steel alloys with 0.1 to 0.4% carbon that have been used up to now. With these chrome-nickel

*) The patent seeker stated as the inventor:

Dr. Benno Strauss in Essen.

Rather, steel alloys will remove the carbon when subsequently heated to about 600 to 900 ^° C., as is the case with e.g. B. is required by welding work when joining individual components, partially separated from the base mass and deposited as chromium carbide at the grain boundaries of the crystal grains after entering into a connection with chromium. The occurrence of this

to Chromkarbides but both of the emergence of a relative to the potential of the crystal grains base potential and leads in the attack of acids or salt solutions to the grain boundaries more or less quickly

»5 Complete disintegration of the alloy, if not heated, and although to a temperature above about 1000 ° C, and subsequent quenching restores the purely austenitic state of the alloy. The one that brings about the purely austenitic state In the case of large objects (containers), however, heat treatment is often not possible at all or perform only with great difficulty.

Nothing is changed in the essence of the invention when using austenitic steel alloys be used, in addition to chromium, nickel and the very low carbon content the Additives that improve the structure, such as B. molybdenum, copper, etc. contain.

Claims (1)

Claim: The use of known austenitic chromium-nickel-steel alloys with z. B. 18 to 25 ° / ₀ chromium, 7 to 12 ° / ₀ nickel and a ^{carbon content below 0.07 1} Y ₀ for the production of such objects to be exposed to the attack of chemical agents, which are either in the manufacturing process, e.g. B. excluded during welding, or the operations of a an annealing treatment equaling heating * 5 are set and in which the alloy is not restored after this ER- ■ warming by quenching from temperatures above about 1000 ⁰ C purely austenitic state.