DE245183C - - Google Patents

Description

IMPERIAL

PATENT OFFICE.

PATENT LETTERING

- M 245183 - ■ CLASS 18 c. GROUP

by means of carbon monoxide.

Patented in the German Empire on August 20, 1908.

The effect of carbon monoxide on steel or steel alloys has already been discussed, more numerous Research and several attempts have been made to investigate the charring effect of this gas for the industrial cementation of objects made of steel or steel alloys.

The research, however, has come to contradicting results because during many, on the basis of experiments, asserted that carbon monoxide had weak carbohydrates can produce, have others (and in more recent times and due to extremely precise Experiments) claims that carbon oxide cannot cement steel at all. To the latter Conclusions reached z. B. R. Bruch in his in the magazine "Metallurgie" (headed von Borchers & Wüst, Vol. Ill, pp. 123 to 128) published trials.

Nobody, however, had ever thought of the possibility of using carbon monoxide commercially as a cementing agent to use using its special mode of action to achieve a specific concentration and distribution of the Preserve carbon in the cemented zones; for even those who admit that carbon dioxide is able to cement iron, believed that very small traces of carbonic anhydride, which are form when the carbon oxide begins to give up carbon to the iron and the same to cement, are sufficient to prevent the carbonization process from proceeding. Therefore So, on the basis of this assumption, we would have to continue cementing with carbon dioxide to be able to completely remove the slightest traces of carbonic anhydride immediately as they arise be eliminated.

These ideas include in which in "Stahl und Eisen", 1906, Vol. I, p. 756, published Articles expressed.

In contrast to the above assumptions now has a number of very precise investigations (carried out with the most careful consideration of the influence, pressure and temperature exert on the equilibrium of the chemical systems between which the reactions causing the cementing effect of the carbon monoxide take place) two new ones Facts demonstrated, namely:

1. that you can change the temperature (and possibly the pressure) the cementing effect of the carbon monoxide can strengthen or weaken at will;

2. That with "regeneration" of the carbon monoxide the carbonizing effect of the carbon monoxide not through complete excretion of carbonic acid anhydride as soon as it occurs, but can be regulated by partial excretion of the same in such a way that the concentration in the cemented zones and distribution of carbon that one desires.

An older cementing process is based on some of these findings

Inventor, in which the partial regeneration of the carbon oxide by using solid, brought into contact with the surface of the steel objects to be cemented Free carbon containing substances is achieved.

More recent studies have now shown that even better results are achieved can if the for partial regeneration

ίο of carbon dioxide used solid, free carbonaceous substances (at least during part of the cementation) do not are in direct contact with the surface of the objects to be cemented.

This new process allows the concentration and distribution of carbon in the cemented zones within much wider limits than the method mentioned above be managed; because with the new process, the cementing temperature can be independent can be regulated by the temperature at which the partial regeneration of the carbon dioxide takes place carries out what is evidently done in the above-mentioned process, in which the two reactions come into contact with one another standing solid masses (coal and steel) can not be the case.

Best of all, the novelty and importance of the achievable by the new process Results are explained using a practical embodiment.

Let us assume that you want objects made of soft according to the new process Cement steel of the following composition:

Carbon 0.11 percent,

Manganese 0.36

Silicon 0.02

Sulfur 0.03

Phosphorus 0.04

and the regeneration of the carbon monoxide is said to be effected by charcoal at a constant temperature of 1200 ° C. Now, if the charcoal (as in the above procedure) would be in contact with the to be cemented steel articles, as well as the cementation at 1200 ⁰ C. apparently would have to take place, and if, in this case, the concentration of carbon in the cemented zones within somewhat more If limits were to take place, one would have to subject the pressure of the carbon dioxide to great changes.

On the other hand, let's see what kind of results one can achieve when looking for the new one Proceeding, d. H. if the charcoal used to regenerate the carbon dioxide not brought into contact with the steel objects to be cemented, but in another container or in the part of the cementing chamber is heated, welehe from the part where said objects are located, so that, even when the temperature at which the regeneration of the carbon dioxide takes place is constant is obtained, the temperature of the objects to be cemented changed and therefore can be chosen favorably.

It is also assumed that in each case the carbon monoxide is stored in the cementation tank circulates so that every hour with the objects to be cemented approximately ι cbm of "regenerated" carbon oxide (at 1200 ° C.) comes into contact per square meter of steel surface to be cemented, and that in each In case the cementation takes about 20 hours.

The concentration of carbon in the cemented zones then changes with it the change in the temperature of the pieces to be cemented and the gas pressure as follows (The exposition here, of course, for the sake of clarity, is divided into two groups united cases):

a) Let the pressure chosen (to be maintained continuously for the entire duration of each operation) be ordinary atmospheric pressure. If in this case the objects to be cemented are heated to different temperatures, the following results are obtained: ■ - -

temperature

the one to be cemented

Objects

iioo ° C,

looo ⁰ C.

900 ° C:

Maximum concentration

of carbon in the

scored cemented

Zones

0.35 percent 0.52 -

0) 75

b) When cementing under a slightly higher pressure, namely of 2 atmospheres, the following results are obtained:

temperature

the one to be cemented

Objects

iioo ° C.

iooo ⁰ C.

900 ⁰ C.

Maximum concentration

of carbon in the

obtained cemented

Zones

0.72 percent 0.86 .1.05

It can therefore be seen that if one follows the new procedure under certain conditions (especially with regard to temperature and pressure), cemented zones are achieved

at which the maximum value of the carbon concentration (of course in the outer layers) is a definite one. In addition, one can do this by having the two Main factors, namely temperature and pressure, changed within fairly limited limits, in the cemented zones (always precisely defined) variable within very wide limits Achieve carbon concentrations;

ίο yes it is sufficient to change only one of the two factors (e.g. the temperature), significant changes in carbon concentration in the cemented zones to get. ^ This is readily apparent from a comparison of the figures in the two tables above.

These results are apparently entirely new.

After the

Features of the new process that have been highlighted can be seen for its use in the various cases the following general rules, which are slightly different from the equilibrium relationships the reactions that produce the carbon dioxide effect and are confirmed by experience, set up as a guideline:

The cementing effect of carbon dioxide is based on the reversible equation:

(1) 2 CO ^ z ± CO ₂ + O =

which takes place in the system formed by the carbon dioxide (CO) used, the carbonic acid anhydride (CO ₂ ) that forms as the cementation progresses, and the carbon C which is formed in the steel as the cementation progresses into solid solution.

It is clear that the cementation continues as long as the above equation can continue from left to right, since in this case the concentration of carbon C in the cemented zone continues to increase, whereas the carbon concentration stops increasing when the concentration increases of the three constituents (CO, CO ₂ and C) have reached values corresponding to the equilibrium ratio of reaction (1). Obviously, one must be able to derive the practical norms from the equilibrium conditions of reaction (1) in order to regulate the carbon concentration in the cemented zones at will.

Indeed, considering the fact that reaction (1) is different (from left to right) exothermic and with a decrease in gas volume takes place, the following derive rules that are fully confirmed by commercial practice:

I. With otherwise completely the same conditions (especially under consistently constant Temperature of the items to be cemented) is the carbon concentration in the cemented The higher the temperature at which the partial "regeneration" takes place, the higher the zones of carbon dioxide takes place.

2. With otherwise completely the same conditions (especially if the conditions remain the same all the time the temperature at which the partial "regeneration" of the carbon oxide takes place) the carbon concentration in the cemented The higher the temperature of the objects to be cemented, the smaller the zones.

3. All other things being equal, the carbon concentration is in the cemented The higher the pressure of the carbonization gases, the higher the zones.

4. All other things being equal, the carbon concentration is in the cemented The larger the zones during the operation over a certain length, the higher the zones The quantity of "regenerated" carbon dioxide conducted is the amount of steel to be cemented.

5. All other things being equal, the carbon concentration in the cemented one increases Zones closed if hydrocarbons or vapors of liquid hydrocarbons are added to the carbon monoxide are added, namely the increase in carbon concentration is greater, the greater the addition of hydrocarbons is. .

It is therefore evident from the foregoing that by applying one or more of these norms (based on the results of the experimental samples explained above by way of an example) cemented zones can be achieved in which the carbon has a certain concentration and has distribution.

• It is also clear the present procedure in many cases can also be used in conjunction with the above, by the operation for a certain period of time according to the norms laid down by the introduction and one for another time by the other method (i.e. with the carbon in contact with the steel to be cemented).

The steel objects produced by the present process can then be used to achieve the desired properties to the usual mechanical treatments (rolling, Forging, etc.) as well as thermal treatments (hardening, annealing, etc.) will.

Finally, it should not go unmentioned that another important practical advantage of the new cementing process is that in the carbonized obtained by the process Zones the change in the carbon concentration in the successive layers an extraordinarily uniform and is gradual, so that in the case of steel objects cemented by the present process never those of sudden change

the carbon concentration in the cemented Zones resulting from fragility and exfoliation occurs, while known - these (very harmful and often dangerous) phenomena with great frequency in after common methods of cemented steel objects.

Claims (1)

Patent claim: ίο method of cementing objects made of steel or steel alloys by means of carbon oxide, which during the cementing process is constantly partially regenerated by solid substances containing free carbon, such as charcoal etc., thereby characterized in that the substances used to regenerate the carbon dioxide are out of contact with those to be cemented during part of the cementing process Objects are kept at the cementing temperature regardless to be able to regulate the temperature at which the partial regeneration of the carbon oxide takes place.