DE1053013B - Process for preventing or regulating carbon uptake in powder or gas carburization - Google Patents

Description

GERMAN

The invention relates to a method to prevent certain areas of a steel part from being carburized or to protect the carbonitriding effect of reaction gases more or less.

Methods are known by which those surfaces of a workpiece are protected by covering to which the carbon of the reaction gases should not diffuse. Used for this For example, kneadable masses, pastes or liquid protective masses. The work pieces are dipped in or with the Sohutzwjasses painted and then air dried.

As such covering means is used, for. B. pastes containing iron oxide. Here the iron oxide serves as oxygen-releasing agent that the carburizing carbon monoxide to carbon dioxide, d. H. to a inert protective gas oxidized.

Workpieces that are coated with such a covering agent are not or at these points less carburized.

The invention relates to oxygen-releasing agents, but not as firmly adhering coatings, but come as moldings for use. Then iron oxide-containing moldings are proposed, which, due to their location and shape, are able to surround the workpiece to be carburized to form and maintain a carbonic acid gas jacket by reduction. Depending on the concentration This carbonic acid atmosphere makes it possible to use certain workpiece areas to different degrees To expose reaction gases. The invention makes it possible to work on one and the same workpiece to achieve different penetration depths of the reaction gases and finally the same in some areas To prevent any reaction on the workpiece.

Such differentiated carburization is with firmly adhering coatings, as they have been proposed since then were not possible. In addition, the formed from the iron oxide-containing moldings Gas jacket as protection against carburization has significant other advantages over firmly adhering coatings, such as it is obtained by painting on non-shaped cover medium. Apart from that when using The homogeneous Gaismantel provides a substantial effect more even protection than a hand-applied and often uneven protective coating. In addition comes that the molded body, in contrast to the protective coating, does not have a firm connection with the protective workpiece and that accordingly no foreign substances on the surface remain of the same. This is particularly important when the carburized workpieces cool down in the oil

Method of prevention

or regulation of carbon uptake in powder or gas carburization

Applicant:

Dipl.-Ing. Alex Schweizer,
Hofheim (Taunus), Im Klingen 1

Dipl.-Ing. Alex Schweizer, Hofheim (Taunus),
has been named as the inventor

bad, since no contamination of the oil from covering agents can occur here.

Moldings containing iron oxide finally have the advantage of being relatively easy to regenerate, by annealing them after use in an oxygen-containing atmosphere at around 500 ° C. You arrive thereby for the most part back to their original chemical state, and they also retain them essentially their old form and adaptability.

To produce the moldings themselves, binders such as water glass are used. aside from that the shaped bodies can be diluted by a filler such as aluminum oxide, clay or sand.

In this way it is possible to control the strength of the oxygen release and thus, as already mentioned, the depth of penetration of the reaction gases and the thickness of the carburization layer vary as required to influence.

The use of an oxygen-releasing molded body according to the invention is described below using an example: The drive bevel gear 1 shown in the drawing is to be surface-hardened to a depth of 0.7 to 0.9 mm after its mechanical processing, but the thread 2 on the lower end of the shaft should remain soft. For this purpose, cylindrical metal pieces with a base are made, as shown in section in the drawing (3). These metal vessels are expediently made of copper. An oxygen-releasing shaped body (tablet 4) is placed on the bottom of each metal vessel. This consists of hammer blows or scale, which is predominantly Fe ₃ O ₄ and in every forging shop in

809 770.334

large amounts, also from clay and sand as well as from water glass as a binding agent. For example make 4.7 parts of scale, 2.4 parts of clay, 1.2 parts of sand and 1.7 TeMe water glass a well malleable mass.

The composition can, however, with good results contain between 4 and 6 parts by weight of scale, remainder Clay, sand, water glass and other fillers, as well as binders - to a total of 10 parts - varied will.

Now the shaft of the drive bevel gear with the thread 2 is placed in the metal vessel, like this can be seen from the drawing. The inner diameter of the metal vessel should not be more than 1 to 2 mm larger than the pressure gauge of the surfaces to be protected, in the present case as the outer diameter of the thread 2.

The workpieces prepared in this way are then carburized in gas or powder in a carburizing system of known design. In the case of gas carburizing, the supplied carburizing gas can e.g. B. have the following composition: 53% H ₂ , 18% CO, remainder N ₂ and an addition of C ₃ H ₈ . The carbonization temperature is up to 920 ° C.

The following processes take place during carburization: The carburizing gas hits the unprotected Surfaces of the bevel gear 1 its carbon from the steel:

3 Fe + 2 CO - Fe ₃ C + CO ₂

In the area of the oxygen-releasing shaped body, d. H. on the thread 2 of the bevel gear to be protected, on the other hand, the following reactions take place:

Fe ₂ O ₃ + CO-2 FeO + CO ₂

₈₄ y

Fe ₂ O ₃ + H ₂ -2 Fe O + H ₂ O and further

H ₂ O + CO-

-H.

+ CO,

That is, in all cases, the iron oxide of the molded body makes the carburizing carbon oxide ineffective made and turned into inert carbon dioxide. Since it is specifically heavier than the carburizing gas, it does not escape from the shelter.

After about 10 hours the boiling process is over, and the workpieces are removed from the system. After cooling down, the metal vessels 3 and the used shaped body (tablet 4) removed. If you cut the workpiece along its Longitudinal axis and makes the carburization layer visible in a known way, so one finds in the unprotected Area a uniform carburization layer, whereas the thread 2 as a result of the described Procedures have remained unchanged.

Instead of being made of copper, the vessel 3 can also be made directly as a shaped body from the oxygen-releasing material Means, that is to say from a material with the same composition as the tablet 4, are produced, but may then only cover the parts to be protected.

If the inner surfaces of a workpiece before the

Ingress of the reaction gases are to be protected, one proceeds analogously, before the treatment in the oven

z. B. extruded moldings are given in cavities of the workpieces and these spaces at their Ends are closed or covered in a suitable manner.

Claims (5)

Patent claims: 1. Process for preventing or regulating the uptake of carbon in powder or Gas carburization at certain points of the workpieces to be carburized using oxygen-emitting Agents such as iron oxide, characterized in that 40 to 60% hammer blow with fillers and binders to form a molded body shaped, surrounding the areas to be protected as close as possible. 2. The method according to claim 1, characterized in that the filler is aluminum oxide, clay or sand can be used. 3. The method of claim 1
draws that as a binder is turned. 4. The method of claim 1
draws that the shaped body Tablet, an extruded profile or a Plate has. 5. The method according to claim 1, characterized in that the molded body is housed in metallic vessels, which adapt to the erkstückflächen to be protected W ^T. , thus marked water glass , thereby recognizing the shape of a Considered publications:
German patent specification No. 307 991. 1 sheet of drawings © 809 770/334 3. 59