US2025050A - Cementing agent for steel and iron - Google Patents

Description

Dec 24, 1935. H. HANUscH l 2,025,050

CEMENTING AGENTFOR STEEL AND IRON v l Filed'Nov. s, 19314 Patented Dec. 24, 1935 UNITED STATES ,PATENT ori-ICE CEMENTINGv AGENT FOR STEEL AND IRON Hugo Hanlsch, Berlin, Germany, assigner to E. F. I

Houghton & Company, Philadelphia, Pa.

application November 3, 1931, serial No. 572,859l In Germany November 8, 1930 claims.

ening process at the present time are characterized by a high content of cyanide compounds. In order to increase the penetratingeiect of the cementing bath it had heretofore been necessary to increase the content oi cyanide in the bath. In consequence of this, for instance, cementing salts having a content of sodium cyanide of 45, 75 and even up to 98% are being put on the market by prominent concerns. v

However, on account of its poisonous qualities a salt bath of this kindis a continuous source of danger.

In a general-way my' invention is based upon the discovery thatit is possible to make cementing salt baths and solid cementing agents '(carburizers) which contain either no' cyanogen at all or little lcyanogen and in spite of this possess a great cementing penetration, if as a carbonaceous agent a carbon is used to which there have beenv imparted by previous physical or chemical'treatment, special properties expediting the process of cementation.

Upto the present time it had not been possible to incorporate in the bath a quantity of carbon suilicient to obtain a deep cementation. It hasY been found that the kind of carbon which has so far been used in cementing baths would separate from the salts and rise to the surface of the bath,

0 where it will burn quickly through the action of the oxygen of the air. In consequence of this no -intensive carburization of the work-,piece could` be attained.

, My invention is based upon the discovery that Y 45 a deep cementing eiect can be attained by means of carbon which is especially suitable for this purpose, that is a carbon which has been subiected to a physical or chemical' treatment with a view to activating said carbon, thereby reducing 50. its combustibility either in the manner described in the German Patents 453,972 of Decemberg28, 1927, 466,358 of October 5, 1928, and 488,669 of January 3, 1930 or in some other way.

Such carbons are termed herein and inthe aforementioned manner which contain only from 55 55 claims acuvatedcarbon of 10W ombusubiuty.

These carbons, upon being subjected to the lfull flame of a Bunsen burner for a period of two hours, leave a residue of non-combustibles of at l' least 59% by weight of the original sample as distinguished from the ordinary activated c ar- 5 bon, which, uponsubjection to the same tests, leaves a considerably smaller percentage o! noncombustibles.

In accordance with the disclosure of 'German Patent No'. 453,972,'ord inary carbon from any 1b source isfheated to glowing in a suitable vessel with porous or gas-permeable walls, and thereafter submitted while glowing to the action of f oxygen or oxygen-containing gases passed through the carbonmass or through the walls oi 15 said vessel. The German Patent No; 466,358 describes an improvement oi' the process of German Patent No. 453,972 by which everiless combustible activated carbon is prepared by treating granular carbon from any sourcel with a water- 20 glass solution followed by precipitation of the i silicio acid by the action of acids prior to the treatment pi thecarbon as dcribed in the main German Patent No. 453,972. An activated carbon product having'a silicic acid skeleton is pro-r 2 5 i duced which possesses great mechanical strength and may be used advantageously in chemical reactions without losing its shape. The 'German Patent No. 488,669 describes'another method for manufacturing a-highly activated carbon of low 30 combustibility. The carbon is treatedwith inorganic substances in solution, or as colloids', which substances exert a combustion-decreasing in- `fluence, and are precipitated as insoluble oxides by a carbonization process. Priorto carboniza- 3 5 tion, other substances are also added, such as zinc chloride or phosphoric acid to increasethe activity of thevcarbon.` It willbe noted that all of these processes produce anactivated carbon of low combustibility which has proved, in accordance with the lpresent invention. to give novel f and unexpected results when Aemployed in c einenting salt baths. j v

` When using carbon or this kind it will be possible to incorporate a quantity of carbon amountlng to as much as 10% in the cementing bath and thereby to obtain an exceptional penetration. It will also be possible when using l such cementing baths to work at temperatures above 900 C. which will greatly expedite the cementing process but could not be used easily in the present c einenting baths, as the latter are liable`to undergo decomposition at these temperatures. I have succeeded in making up salt baths in the to 98% of sodium cyanide.

4 to 6% of pure cyanogen and in spite of this will eil'ect a. cementation which heretofore could hardly be attained with salts containing from The poisonous and dangerous character of these salt baths will thus be quite considerably reduced with the result that .these new baths do not involve more danger than many machines and processes used in the modern indust-ry. In addition to this, such baths are materially cheaper than salt baths having a high content of cyanide.

The baths may be made up in the usual manner and, besides chlorides, also carbonates and alkalies may be used. The cyanide compounds contained in the baths may consist of sodium cyanide or potassium cyanide, potassium ferrocyanide, calcium cyanamide and so forth.

'I'he following two examples are given to show how the new salt baths may be composed.

On the basis of experiments I have ascertained that with properly composed baths there will be an excellent cementation, also in case -oi solid cementing agents, if at at the same time activated carbon of low combustibility is used in considerable quantities.

Example 3 A Per cent Ordinary carbon 85 Potassium ferro-cyanide 5 Activated carbon of low combustibility 5 Carbonate of barium 5 li'roample 4 Per cent Ordinary carbon Activated carbon of low combustibility 5 Carbonate of barium 5 I have further ,found that the time required for the cementing process may be considerably reduced, ii' the cementing bath is closed hermetically and kept under pressure.

In the drawing I have shown-in diagrammatic vertical section an apparatus which is suitable for carrying out my novel process'ior cementing steel and iron under pressure.

'I'he container I may be hermetically closed by -.means of a coverl 2. and packings 3'; as indicated in the drawing. The gases'which aresbeing'de.- veloped at the cementing temperatures will cause an over-pressure to arise within the container I which over-pressure may be regulated by'means of the valve 4, 5 and controlled by 3a pressure gauge 8. .d The work-piece 1 to be subjected to the cementing process is suspended within the container I and kept immersed in the bath 8 within the container I.- As cementing baths with which -the process oi cementing maybecan'ied out under pressurethere may be used baths of the ai'orementioned kindkas welly as allother cementing baths which had heretofore been used, especially also `cyanogen containing cementing agents known in commerce under various trade-marks or the various cyanide hardening compounds sold under the name of their manufacturers. 5

I claim:

1. An iron and steel cementing bath composition, molten at cementing temperatures and containing material capable of supplying carbon to the metal at said temperatures, comprising an 10 alkali metal cyanide in the neighborhood of 8%, sodium chloride in the neighborhood of- 62% to 65%, potassium chloride in the neighborhood oi I 18% to '19%, and an activated carbon of low combustibility in the neighborhood of 8%'. 15

2. .An iron and steel cementing bath composition, molten at cementing temperatures,and containing material capabl of supplying carbon to the metal at said temperatures, comprising a salt inert to th'e iron and steel molten at vcementing 20 temperatures as the major ingredient of said composition, and at least 4% of activated carbon of low combustibility, the lastl named ingredient supplying carbon to the metal at cementing temperatures. 25

3. An iron and steel cementing bath composition, molten at cementing temperatures and containing material capable oi supplying carbon to the metal at said temperatures, comprising a salt inert t0 the iron and steel molten at cementing 30 temperatures as the major ingredient of said composition, a cyanide compound and. at least 4% of activated carbon of low ,combustibilitm the last named ingredients supplying carbon to the metal at cementing temperatures. *.5

4. An iron and steel cementing bath composition, molten at cementing temperatures and containing material capable oi' supply carbon to the metal at said temperatures. comprising a mixture of salts inert to the iron and steel molten at 40 cementing temperatures' as the major ingredient of said composition, alkali metal cyanide and atleast 4% of activated carbon of low combustibility, the last named ingredients supplying carbon to the metal at cementing temperatures. '4

5. An iron and steel cementing bath composition, molten at cementing temperatures and containing mterial capable 0i' supplying carbon to the metal at said temperatures, comprising a salt inert to the iron and steel molten at cementing 50 temperatures as the major ingredient oi.' said composition, alkali metal cyanide in the neighbor- Y borhood of 8% and activated carbon of low combustibinty between 4% and 10%.the1ast named 5 ingredients supplying carbon to the metal at cementing temperatures. 7. An iron and. steel cementing bath composition, molten at cementing temperatures and containing material capable of supplying carbon 70 to the metal at said temperatures, comprising a salt inert to the iron and steel molten at cementing temperatures as the major ingredient of said composition, alkali metal cyanide in the neighborhood oi 8% and activated carbon of low com- 75 borhood of 2%, and caustic soda in the neighbor-l bustibility in the neighborhood of 8%, the last named ingredients supplying carbon to the metal at cementing temperatures.

8. An iron and steel cementing bath composition, molten at cementing temperatures and containing material capable of supplying carbon to the metal at said temperatures, comprising an alkali metal cyanide in the neighborhood of 8%, sodium chloride in the neighborhood of 62%, po-

tassium'chloride in the neighborhood of 18%, ac-

tivated carbon of low combustibility in the neighborhoodof 8%, barium carbonate in the neigh- 3 temperatures as the major ingredient of said composition, and at least four percent or activated carbon of low combustibility .containing inorganic material within its pores, the said activated carbon supplying carbon to the metal at cementing' temperatures. n

10. An iron and steel cementing bath componition. molten at cementing temperatures, and containing material capable of supplying carbon to the metal at said temperatures, comprising a salt" 10 inert to the iron and steel molten at cementing temperatures as the major ingredient of said composition, and at least four percentof activated carbon of low combustibility having a silicic acid skeleton, the said activated carbonsupply- 15 ing carbon to the metal at cementing temperav tures.

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