US 1480230 A
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Patented 'Jan. 8, 1924.
UNITED STA I OFFICE.
TOYOHCHIBO TASHIBO, 0F TOKYO, JAPAN.
PROCESS OF CARBUBIZING STEEL AND IRON.
To all whom z'tmay condom:
Be it known that I Toroxronmo TA- srrmo, subject of the mperor of Ja an, residin at No. 450 Shirokane Sankoho, Shiba u, Tok 0, Japan, have invented new and useful mprovements in a Process of Carburizing Steel and Iron (for which I have filed application in Japan August 13, 1918, application No. 40,345), of which the following is a specification. g
This invention relates to improvements in the process of carburizin wrought iron, steel or steel alloy, or artic es made thereof, and consists in causing carbon monoxide to form in a carburizing chamber which can be tightly closed and making it toiact in its nascent state and under pressure on the 'ma-' terial to be carburized. The object of this invention is to cause carbon by a simple means to impregnate .deep and in a short time, utilizing reaction heat and pressure.
There are known several carburizing processes, but these may be classed into two.
In the first class, which is characterized by the use of solid carbon 'ving materials, material rich in carbon, sutii as charcoal or the like, or a cyanide, or charcoal mixed with an oxidizing agent, is used, and carbon monoxide is produced. However, in all these processes, although means are taken to preventthe combustion gases entering the carburizing chamber, no attempt: has been made to intercept, at least with intention, gases generated in the carburizing chamber and retain them there, thus increasing pres sure therein, such gases being rather made .nor any usefulgas 1s generate to escape rapidly therefrom.
In the second class, carbon containing gas such as a hydrocarbon, cyanogen, carbon monoxide or the like is burizing chamber, and the iron or steel material is made to take carbon therefrom. Sometimes, charcoal= or the like is put in the carburizing chamber and carburlzing gas mentioned above is forced thereinto, but no oxidizing action takes place between the gas and the charcoal.
Again in processes of the first class, carbon monoxide is formed in the carburizing chamber, but it has not much tendencyto penetrate into the material under treatment, and after remaining in contact therewith for a short time, it escapes there rom, Thus large gas containing carbon is used forced into the car Application fled. Kay 24, 1921. Serial No. 472,282;
the waste of that fias is very great and the effect is very sma Moreover, in the ,carburizing chamber oxidizin takes (place and consequent y reaction heat is pro need; but as the esca ing gas carries out that heat, as much heat is lost as is produced, and the temperature of the chamber 1s never raised by such reaction heat. Thus,
a large quantity of expensive carbu agent is spent but the efi'ect is very slight. According to experiments thus far known, iron was subjected for eight hours to a temperature of 2000 F., using as carbon givin material charcoal mixed with 40% o barium carbonate, and the result was that the material was carburized to a depth of 0.177 inches; and the result obtained by the same process using only charcoal powder without mixing barium carbonate therewith was impregnatlon of carbon to adept-h of 0.138 inches. Notwithstanding the use of a amount of barium carbonate, the result was that the iron was carburlzed 1.28 times deeper than when only carbon without any oxidizing agent is used. No wonder, therefore, that in lar lfactories where armour plates are manu a ctured, there are still many. which use only carbon powder for carburizing pur e.
In the secon class process, a compound for 'ving carbon to the iron. .Or sometimes solid carbon is also kept in the carbu. chamber, but this is useful only for deoxidizing purpose, and no oxidizing action takes place etween the. same and the carbon' givin gas,
onsequently, presence or non-presence of solid carbon has no direct effect on carburizing. Moreover, notwithstanding that it is a very diflicult task to maintain a pressure of from two to four atmospheres in a high temperature of not less than 900 (3., according to this process wrought iron 22 mm. thick must be subjected to such a heat under such a pressure for forty hours.
' My invention is an improvement in the above described processes, and consists in fillinga carburiz-ing chamber, so constructed as to be tightly closed, with iron material and carbonaceous substances, and in causing carbon monoxide to form in the carburizmg chamber, and to act in its nascent action briskly.
state upon theiron material under a presas carbon giving material and oxidizingagent charcoal powder mixed with 25% of mixture of equal parts of iron oxide and manganese peroxide, subject the whole toheat at between 800 and 950 C. for two hours and a half, maintaining the pressure within the carburizing chamber higher than the atmospheric pressure by 0.153 pound per one square inch.
The result will be the carburization of the iron pieces to a depth of 0.5 inches or 13 mm. Even the central part will be found partially converted into steel, points having steel lustre being found interspersed there.
Ewample 2.-Take iron pieces one inch thick, and subject it to the treatment described in Example 1. Then embed the iron pieces thus treated in a mixture of equal parts Example 3.-Take iron pieces 1.2. inches,
or 32 mm., thick of the kind above mentioned, and subject them first to the second treatment described in Example 2; Then, repeat the same treatment but subjecting the iron pieces to a heat above 950 C. and for a longer time, Thus the time during which the iron pieces are subjected to efiicientheat, is five hours and a half. A
Then the iron pieces will be converted into a high carbon steel, small blisters being formed on the surface and a small part of the surface beginning to melt.
use is Japanese knife iron,
of mixture of carbon giving material and oxidizing agent, once used in,
the atmospheric that is for three hours.
ineoeeo In this invention any low grade oxide, or I ore, which frees oxygen at a high temperature and does not contain any injurious ingredient such as sulphur, phosphorus, or the like, may be used a oxidizing agent instead of iron oxide and manganese peroxide. Or, oxidizing agents such as air, oxygen or the like may be introduced from outside. Moreover, carburization may be accelerated by increasing the pressure an temperature, but in this case, a great care must be taken, as the material under treatment will be converted into high carbon steel, and begin to melt, and the treatment will go beyond the limit of carburization. To give a few examples, iron pieces 1.2 inches thick, 1.4 inches broad and 1.6 inches long of the kind of knife steel above mentioned, together with a mixture of charcoal powder with 20% of manganese peroxide, were subjected to a heat not higher than 1200 C. for three hours at a pressure higher than the atmospheric pressure by 0.3 pound per square inch; and the pieces were found wholly converted into a high 'carbon steel and in a half melting condition, a part actually flowing and the pieces being found somewhat changed in its shape. Again, rod one inch square of the same kind of iron were subjected together with charcoal powder mixed with 10% of manganese peroxide to the sameheat as in the above example for two hours and a half at a pressure higher than the atmospheric pressure by 1 pound per square inch and the iron rods melted and were converted to grey pig iron. Tron pieces 1.5 inches thick, 2 inches wide and 2.5 inches long, being heated in a high temperature furnace together with a mixture of 20 parts of manganese peroxide, and 80 parts of charcoal or one hour forty minutes at a pressure higher than the atmospheric pressure by rods of half an inch square, they were perfectly converted into steel after such treatment of one hour. In all the above experiments, cast iron pieces placed in contact with walls of the carburizing chamber for the purpose of adjusting pressure were never melted although they were used several times. This shows that notwithstanding the furnace temperature did not rise to 1220"" (l, the temperature at which grey cast iron melts. the temperature in the interior 'must have been raised by reaction to more than Ill) 142O C., the temperature at which highcarbon steel melts. I
According to my invention, charcoal iron can be carburized in two hours and a half to a depth from 10 to 13 millimeters, and a piece 26 millimeters thick of the same iron can be wholly converted into steel in five hours, giving to the material the mild carburizing treatment. Using the mild and medium carburizing treatments consecutively on a piece of charcoal iron 26 millimeters thick, it can be wholly converted'into high-carbon steel in five hours and a half, and if the high carburizing treatment be given to the same piece, the same result can be obtained in one-half or onethird of that time. Thus the time required to carburize iron using only charcoal powder as hitherto practiced, can be reduced to one hundredth o'r one-two hundredth, and
j the same result as obtained by the process explained above under class 2, can be secured in one tenth or one twentieth of the time required in that process.
The characteristics of the products obiained by my invention are, (1) material .s carburized uniformly, carbon impregnating with comparatively greater uniformity even into the deepest part; (2) from the nature of the invention, the effective gas within the carburizing chamber acts upon the material to be carburized' with equal tension all over its surfaces, and consequently the product is most suited as materlal for manufacturing crucible steel; and (3) as material can be carburized without producing any blister on the surface, my process is best suited for carburizing iron ware.
I claim 1. The process of carburizing iron, steel and the like, which consistsin embeddin the material to be carburized in a bed of a mixture of carboniferous substance and metallic peroxide in a carburizing chamber that can be tightly closed, and causing carbon monoxide to act in its nascent state under a pressure higher than the atmospheric pressure by heating, utilizingthe reaction heat produced when the said carbon monoxide is formed.
2. The process of carburizing iron, steel and the like, which'consists in placin the material in a carburizing chamber,'m1'xing a carbon giving material with iron oxide and manganese peroxide, subjecting the wholes to a heat at a temperature between the approximate limits of 800 and 950C. and maintaining the pressure within the carburizing chamber higher than the atmospheric pressure.
3. The process of carburizing iron, steel manganese peroxide in proportions of apcharcoal powder with iron oxide and manganese peroxide, subjecting the whole to heat at a temperature between the approximate limits of 800 and 950 C. and maintaining the pressure within the carburizing chamber higher than the atmospheric pressure. i
5. The process of carburizing iron, steel and the like, which consists in placing the material in a carburizin chamber, mixing charcoal powder, iron oxide and manganese peroxide in proportions of approximately 75 per cent, 12% per cent and 12% per cent respectively, subjecting the whole to heat at a temperature between the approximate limits of 800 and 950 C; for a period of about 5% hours, and maintaining the pressure within the carburizing chamber higher than the atmospheric pressure by approximately 0.153 pound per square inch.
6. The process of carburizing iron, steel andthe like, which consists in placing the material in a carburizing chamber, mixing a carbon giving material, 1ron oxide and manganese peroxide in proportions of approximately 75 per cent, 12% per cent and 12% per cent respectively, subjecting the whole to heat at a temperature between the approximate limits of 800 and 950 for a period of about 2 hours, and maintaining the pressure within the carburizing chamber higher than the atmospheric pressure by approximately 0.153 pound per square inch, then embedding the material in a mixture of equal parts of carbon giving material and oxidizing agent mixed with about 20 per cent of lIOIl oxide, subjecting the whole to heat at a temperature between the approximate limits of 800 and 950 C. for a further period of approximately 2%; hours, and maintaining the pressure within the carburizing chamber higher than the atmospheric square inch.
7. The process of carburizing iron, steel and the like, which consists in placing the material in a carburizing chamber, embedding the material in ya mixtureof equal parts of carbon giving material and oxidizing agent mixed with about 20 per cent of iron oxide, then subjecting the whole to heat at a temperature between the approximate limits of 800 and 950 C. for a period of approximately hours, maintaining the 4L 4 ineo aao pressure within the carburizing chamber whole to heat at a temperature in excess of higher than the atmospheric pressure by a 950 (3., for a further period of approxiproximately 0.285 pound per square inc mate-1y 3 hours and maintaining the same 10 then embedding the material in a mixture of pressure within the carburizing chamber.
(- equal parts of carbon giving material and In testimony whereof I have signed my oxidizing agent mixed with about 20 per name to this specification.
cent of iron oxide, again subjecting the TO'YUKICHIRQ TASHIRO.