US3332809A - Sulphurizing treatment of iron and steel - Google Patents

Description

July 25, 1967 Fil'ed Oct. 8, 1963 FIG.

FIG.

United States Patent 3,332,809 SULPHURIZING TREATMENT OF IRON AND STEEL Yukio Tanaka, Tokyo-to, Akira Furusawa, Yokohamashi, and Kosaku Isobe, Tokyo-to, Japan, assignors to Kokusai Denki Kabushiki Kaisha, Tokyo-to, Japan, a joint-stock company of Japan Filed Oct. 8, 1963, Ser. No. 314,770

Claims priority, application Japan, Nov. 28, 1962,

37/52,163; Jan. 31, 1963, 38/4,099; Mar. 8, 1963,

38/10,573, 38/10,576 2 Claims. (Cl. 148-635) The present invention relates to techniques in the treatment of surfaces of materials, particularly iron and steel. More specifically, the invention relates to new and improved method and means for sulphurizing surfaces of iron and steel to effect surface treatment thereof.

Conventional methods for sulfurizing of iron and steel as practiced heretofore have been accompanied by certain difficulties and deficiencies, particularly in the sulfurizing agents (hereinafter referred to as sulfur penetrants) used, as will be described hereinafter.

It is an object of the present invention, in its broader aspects, to overcome such difficulties and deficiencies experienced heretofore.

More specifically, it is an object of the present invention to provide a new and improved method of sulfurizing articles of iron and steel. The invention, in one aspect thereof, contemplates accomplishing such surface treatment through the use of a solid sulfur penetrant and, in another aspect thereof, contemplates accomplishing the treatment through the use of a gaseous sulfur penetrant.

It is another object of the invention to provide new and improved sulfur penetrants, particularly a solid sulfur penetrant, suitable for use in the method of the invention.

It is still another object to provide new and improved apparatus suitable for practicing the method of the invention.

It is a further and general object to afford economy, convenience, and simplicity of method and means and other advantages in the achievement of the objects of the invention.

The foregoing objects, as well as other objects and advantages as will presently become apparent, have been achieved by the present invention, the nature and details of which will be best understood by reference to the following description of preferred embodiments of the invention when taken in conjunction with the accompanying drawing in which like parts are designated by like reference characters, and in which:

FIGURE 1 is an elevational view,.in vertical section, indicating one embodiment of the method according to the invention;

FIGURE 2 is an elevational view, in vertical section, indicating another embodiment of the method of the invention; and

FIGURE 3 is an elevational view, in vertical section, showing an embodiment of apparatus suitable for the practice of the present invention.

In one of its aspects, the present invention provides a sulphurizing method which, briefly described, comprises burying an article to be treated in a powder mixture of, for example, a non-crystalline carbon powder,

such as carbon powder produced from heavy oil having a high sulfur content, containing sulfur and hydrogen, and heating the same to a temperature between 400 and 600 degrees C.

In one embodiment of the invention, a graphite crucible 1, as shown in FIGURE 1, is filled with the noncrystalline carbon powder 2 produced from heavy oil having high sulfur content. An iron or steel material 3 "ice constituting the metal article to be treated is buried in this powder. A lid 4 is placed in position to cover the crucible 1, and a sealing material 5 is applied to seal the seam between the cover 4 and the crucible 1. The crucible 1 so prepared is then heated to approximately 575 degrees C. and maintained at this temperature for a certain time, whereupon a sulfurized layer is formed on the surface of the material 3 so treated. The carbon powder, together with the treated metal article buried therein, is then cooled to a temperature below degrees C. before the article is removed from the crucible. This step is taken to prevent the article, while at a high temperature, from contacting O in the air.

To facilitate a clearer understanding of the abovedescribed process, a specific example of its application is described below.

Example 1 A piece of iron designated by the trademark name of Armco of l8-mm. diameter and 10-mm. thickness was buried in approximately 50 grams of the above-mentioned carbon powder placed in and filling a graphite crucible and, after placement of the lid and sealing with the sealing material, was heated for 2 hours at the above-stated temperature of 575 degrees C. The iron piece was thencooled, together with the carbon powder, to a temperature below 100 degrees C. and then removed from the crucible. As a result, a sulfurizing layer of approximately 0.3 mm. average thickness was obtained.

It was further found that the sulfur content of the carbon powder by the above process reached approximately 3 percent, and the volumetric contents of the gases generated by this sulfurcontent at 575 degrees C. were as follows: 6.92 percent H S; 1.5 percent S0 1.76 percent CS 17.3 percent CO remainder N where 0 comes to the air occluded in the powder.

That is, the sulfur S becomes H 8, S0 and CS and, assuming the vapor phase without going through the liquid phase, acts on the article being treated. In this case, these gases dissociate under the catalytic action of the iron material being treated to produce atomic-state sulfur. This atomic sulfur reacts with the iron material to form at least one sulfide, Fe S, and exhibits the so-called sul-' phurizing effect.

The reason for using a carbon powder prepared from heavy oil with a high sulfur content is that such a carbon powder makes possible low-cost generation of H 8, S0 and CS which facilitate the generation of atomic sulfur. It will be obvious that such a carbon powder produced synthetically with a sulfur content of the order of 1 to 3 percent can also be used.

cost. In contrast, the sulfur penetrant according to the present invention is a solid which is easily handled and can be produced at low cost.

Briefly described, the sulfur penetrant of the invention is composed essentially of carbon powder having fixed thereto principally hydrogen in the form of a quinone radial and sulfur content in the form of free sulfur.

One practical embodiment of the sulfur penetrant according to the invention is a granulated amorphous carbon powder having a particle size distribution of approximately 30 to 100 meshes, an apparent (or bulk) specific gravity of approximately 0.27 to 0.4, a sulfur content of approximately 3 percent, and a quinone radical content of 0.6 percent. It has been found that when this sulfur penetrant is placed in a graphite crucible and heated to approximately 575 degrees C., the generated gas, on the basis of 100 cc., is composed of approximately 7.9 percent of H 8, approximately 1.76 percent of CS 1.5 percent of S0 19.5 percent of CO and remainder of N The presence of nitrogen and oxygen is due to the air existing with the penetrant within the crucible.

In the case wherein only free sulfur is used, FeS is merely formed on the surface of the iron or steel article, as is well known. This FeS contributes nothing to wear resistance for friction, which is the purpose of sulfurizing treatment, but, rather, is detrimental to the article. It has been found that, on the other hand, the presence of C and the H in the quinone radical causes the free S to become H 8 at the required heating temperature, and this gas, H 8, upon contacting the iron or steel, causes the formation of a sulfurized layer of Fe S, thereby causing wear resistance to be exhibited. It has been found further as a result of X-ray analysis that the value of this quantity 1x is approximately 0.9, wherefore the aforesaid molecule is Fe S.

The performance of the sulfur penetrant according to the invention has been studied experimentally, and it has been found that, as one aspect of performance, the quantity of the penetrant necessary per one square centimeter of surface area to form a sulfurized layer of approximately (14 mm. thickness on the surface of an iron or steel article is approximately grams.

The carbon powder of the invention as described above can be readily produced, for example, by oil cracking of a heavy 'oil having an amply high sulfur content. Since the H obtained as a by-product during such a process can be advantageously utilized, the invention has the afore-mentioned advantage of low production cost.

In another embodiment of the method of the present invention, the sulfurizing of iron and steel is greatly improved through the use of H 8, CS or a mixture of the two, and rapid sulfurizing treatment can be accomplished.

An apparatus suitable for the practice of this embodiment comprises a crucible 1 (for example, of graphite), as indicated diagrammatically in FIGURE 2, provided in its interior with an intermediate shelf 5 consisting of a gas-porous plate and a gas inlet pipe 7a for supplying H S gas into the chamber below the shelf 5. In the practice of this method, the space in the crucible 1 above the shelf 5 is filled with carbon black 2, in which an article 3 to be treated is buried. Then, H 8 gas is supplied through the gas inlet pipe 7a, through the shelf 5 in the direction of the arrows X, and uniformly into the carbon black 2. The shelf is available to this purpose. The crucible 1 is heated to and maintained at a suitable sulfurizing temperature, for example, 575 degrees C. The crucible 1 may be heated by any suitable method, one such method being to immerse the crucible in a carbon environment within an electric furnace of the fluid particle type.

The above-described process will be better understood by consideration of the following example of typical application.

Example 2 50 grams of carbon black were placed in a graphite crucible on an intermediate gas-porous shelf, and a disk of so-called Armco material of 18-min. diameter and 10-min. thickness was buried in the carbon black. H 8 gas was supplied upwardly through the intermediate shelf into the carbon black at a fiowrate of 0.1 liter per minute, and the crucible was heated for two hours at 575 degrees C. The disk was then cooled, together with the carbon black, to a temperature below 100 degrees C. and then removed from the crucible. As a result, a sulfurizing layer of (LS-mm. thickness having a composition of Fe S was obtained on the surface of the disk.

In comparison, a sulfurizing layer of only 0.2-mm. thickness can be obtained by the conventional method, that is, the method wherein only H S gas is used without the use of carbon black. The reason for this is believed to be that the hydrogen released from H 8 during the sulphurizing treatment remains as spurious matter on the surface of the article being treated, and the apparent concentration of the H S is diluted by this spurious hydrogen, whereas, when carbon black is present as in the case of the present invention, this carbon black adsorbs the spurious hydrogen, Wherefore the sulfurizing effect is increased accordingly.

It has been found that, other than the H 5 for the process gas supplied, CS gas or a mixture of H 8 and CS gases produce equivalent results.

The present invention, in still another aspect thereof, provides an apparatus suitable for practicing the abovedisclosed method of the invention.

As mentioned briefly hereinbefore, it is necessary, after the heating process step of the method of this invention, to cool the treated article, still in its position in the carbon powder within the crucible, until the temperature of the article has dropped to degrees C. or lower and then to take it out since its contact with air while at a high temperature is undesirable. The present invention provides an apparatus which is adapted to accomplish this cooling step in a simple and effective manner. The details of this apparatus will now be described with respect to a preferred embodiment.

Referring to FIGURE 3, the essential parts of the apparatus are: a crucible 1 (for example, a graphite crucible) having a lid 4; a gas-porous plate 5 horizontally disposed from wall to wall across the interior of the crucible 1 with a space of height d between the lower surface of the plate 5 and the bottom of the crucible 1; as gas inlet pipe 7 extending downwardly through the lid 4, through the crucible interior space above the plate 5, and through the 5 into the space therebelow; and a gas exhaust pipe 6 provided through the lid 4. The inlet and exhaust pipes 7 and 6 are provided, respectively, with valves 9 and 10-. During operation, the space within the crucible 1, above the plate 5, is filled with a carbon powder, and an article to be treated is buried within this powder as has been described hereinbefore.

For the heating step of the method according to this invention, the above'described combination of parts is heated by any suitable means. In the instant embodiment, this combination of parts is placed within and heated by a fluid carbon-particle, environmental medium 8 contained within the vessel 11 of a fluid-particle electric furnace.

The apparatus of the above-described construction is suitable for carrying out the method according to the present invention as illustrated by Examples 1 and 2 set forth hereinbefore. In the case of the process of Example 1, the two valves 9 and 10 are kept closed during the heating step. In the case of the process of Example 2, the gas inlet pipe 7 is used to supply H 8 gas into the carbon powder 2 upwardly through the gas-porous plate 5.

In either case, the valves 9 and 10 are opened after the beating step, and an inert gas (for example, nitrogen gas) is supplied at a certain flowrate and discharged through the gas exhaust pipe 6. It has been found that, in the case of the quantities specified in Examples 1 and 2, an inert gas supplied at a flowrate of 10 cc./minute rapidly cools the article 3 after heating treatment to a temperature below 100 degrees C. in approximately 15 minutes without causing any chemical reaction in the article 3 and the sulfur penetrant material 2.

It has been confirmed, further, that by the use of the above-described apparatus in the above manner, there is no possibility of drawing outside air into the crucible interior while the article 3 is still at a high temperature, and, moreover, that the surface of the article 3 taken out after cooling from the crucible is free of irregularities and defects.

It should be mentioned that if the coolant gas is supplied directly without the use of the gas-porous plate 5,

the gas will concentrate locally and flow rapidly toward the opening of the gas exhaust pipe 6, wherefore the cooling effect Will be deficient.

It will be thus observed that the above-described apparatus according to the invention of relatively simple construction and operation not only makes possible the practice of the method of this invention but also affords rapid cooling thereafter of the article being treated without causing oxidation thereof.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. Method of sulfurizing iron and steel articles, com- References Cited UNITED STATES PATENTS 949,500 2/1910 Rees 148--6.35 1,5 62,13 8 11/ 1925 Becker l486.24 2,874,480 2/ 1959 Todd.

2,914,432 11/1959 Singer 148-635 X 2,972,501 2/ 1961 Feinman.

ALFRED L. LEAVITT, Primary Examiner.

J. R. BA'ITEN, JR., Assistant Examiner.

Claims (1)

1. METHOD OF SULFURIZING IRON AND STELL ARTICLES, COMPRISING BURYING THE ARTICLE IN AMORPHOUS CARBON POWDER CONTAINING SULFUR AND HYDROGEN AND HEATING THE POWDER TOGETHER WITH THE ARTICLE BURIED THEREIN AT A TEMPERATURE WITHIN THE RANGE OF FROM 400 TO 600*C.

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