DE823887C - Hardening of work pieces made of iron - Google Patents

Description

Case hardening of workpieces made of iron The invention relates to a Process for the use of beards and aims at an in economic terms and in With regard to its regular implementation, improved method for carburizing and To create nitriding of iron products.

In the case of the case hardening method according to the invention, the workpieces treated with a mixture of nitriding and carburizing gases, which are combustible Contains components including C O and C H4 in proportional proportions, which result in a useful working layer.

It has been found that these proportions are within 2 '/ z up to 5% of nitrating and 97% = 1 »s 95% of carburizing gas at treatment temperatures of mild steel are between 85o and 95o'C. Also something below or above the specified proportional amounts of nitriding gas can be used when using carburizing gases with special properties or in the case of treatment of especially alloyed steels may be useful.

Preferably, the combustible components of the carburizing gases consist essentially of CO, C H4 and H2, the proportional amounts of the carburizing components advantageously in the range of to to 80% for CO and from to to 40% for CH4, based on the total volume, lie. The proportional amounts are given in percent by volume.

The use of significantly smaller amounts of C O and C H4 is although this causes a carburization; can take place, for economic reasons with Consideration of the time factor not promising.

The one to be used preferably from a technical point of view Carburizing gas is town gas, which has been treated in such a way that everything is C 02, 01 and the sulfur components and water vapor have been removed.

For example, a typical upgraded town gas is as follows Composition: C02 = missing 0Q = missing H2 O = missing S = negligible CO = 19.00 / 0 HZ = 48.00 / 0 CH4 = 24, O0 / 0 traces of other gaseous hydrocarbons Remainder N ..

The nitriding gas commonly used is anhydrous ammonia (if possible in the form of partially cracked ammonia).

Raw town gas in the sense understood here is a gas, its Analysis taking into account the prerequisites usually present at gas companies usually something like this: carbon dioxide ...... 2 to 5 0/0 oxygen .......... 0.5 to i 0/0 water. . . . . . . . . . . . o, i to 2 0/0 unsaturated Hydrocarbons e ...... 45 to 3.5% carbon monoxide .... 14 to 20% methane. . . . . . . . . . . . 15 to 30 0/0 oxygen .......... 45 to 55 0/0. The rest consists of nitrogen and about 1.5 to 2 g of sulfur per cubic meter.

Under current conditions it is not common to wash out benzene, Instead, the aim is to gain more gas, with the coal used as the cause the sulfur content of the same. Under these conditions it is with a sulfur content, which may increase up to 6 g per cubic meter and a content of unsaturated Hydrocarbons, including gasoline, naphthalene, anthracene and their Wash homologues, up to 5% or more, by conventional methods.

If ammonia is used together with raw town gas, it exists its effect is partly to counteract the influences of the undesired components. Therefore, when using "raw town gas", more ammonia is required than when using treated town gas.

Also similar or equivalent industrial gases with flammable components, consisting essentially of C O and C H4 can be used, viz both processed or raw, depending on their analysis and the amounts of used Ammonia.

Treatment examples are given below for an effective treatment time t of 6 hours for a mild steel with an initial carbon content of 0.19% using typical unwashed raw town gas and anhydrous ammonia at a temperature of 925 ° C, with the gases prior to entering the Reaction chamber are mixed in the ratio determined to be suitable to achieve a usable insert layer. It should be noted that it is difficult or impossible to experimentally obtain very precise limits on the proportions of the gas quantities because too many variables have to be taken into account, for example the exact gas composition, the composition of the iron alloy and the treatment temperature chosen. However, it has been experimentally found that the practical limit of the ratio of the amount of nitriding to that of the carburizing gas can be changed little from the preferred limits given above.

At temperatures of goo ° C, for a given ratio, the The operating layer depth is low, the carbon content is high and the nitrogen content is high tends to increase.

To get the desired texture of the insert layer in the most effective steels of special composition can be obtained in the most economical way be used.

Claims (4)

PATEN TANSPBLCHE: i. Process for case hardening workpieces made of iron for the purpose of achieving a directly usable insert layer, characterized in that the workpieces are treated at Temperaturdn of between 85o and 95o ° C in an atmosphere consisting of carburizing and nitriding gas, the content of nitriding Gas is 2 '/ 2 to 5% of the total volume. 2. The method according to claim i, characterized in that the atmosphere from 95 to 97 1/2 volume percent of carburizing gas and 2 1/2 to 5 volume percent ammonia consists. 3. The method according to claim t or 2, characterized in that that the workpieces at temperatures of between 85o and 95o ° C in an atmosphere are treated, which consist of 95 to 97I / 2 percent by volume of crude town gas and 21/4 to 5 percent by volume ammonia. 4. The method according to claim t or 2, characterized in that that the workpieces are at temperatures between 85o and 95o ° C in an atmosphere, the city gas made from 95 to 971 / q volume percent processed town gas and 21/2 to 5% ammonia exists, to be treated.