Abstract: A method for carburizing austenitic metal comprising fluorinating the austenitic metal and consecutive carburizing at a low temperature not more than 680.degree. C. A carburizing temperature can be lowered by such a fluorination. As a result, carbide of chrome component in the austenitic metal can be prevented from depositing. That is, much chrome component remains in the austenitic metal. Therefore, the austenitic metal surface can be hardened and also superior anti-corrosion property can be maintained.

Abstract: The present invention relates to nickel alloy products with their surfaces nitrided and hardened which are formed by pressure casting nickel alloy material, and nitrided and hardened layers are formed in surface layers. Since the nitrided and hardened surfaces of the nickel alloy products according to the invention have much better corrosion resistance than iron products have, anticorrosion treatment such as plating is not required, and rich lubricity and excellent tightening property can be obtained without having seizure and scuffing phenomena.

Abstract: This invention allows to form a nitrided hard layer on the surface of an austenitic stainless steel screw by forming a nitrided layer thereon and to prevent causing rust on some parts such as a screw head portion which is in contact with the outside air by removing the nitrided hard layer to expose austenitic stainless steel base which has sufficient corrosion resistance. On the contrary, in a thread part and the like of the screw, the nitrided hard layer is left and to thereby improves hardness and the like to strengthen tapping functions and the like of the screw. In the method for manufacturing the austenitic stainless steel screw according to the invention, the austenitic stainless steel screw is held in a fluorine- or fluoride-containing gas atmosphere prior to nitriding to form a fluorided film on its surface and then is nitrided in that state. Accordingly, so formed nitrided hard layer becomes uniform and deep to obtain an austenitic stainless steel screw having excellent surface properties.

Abstract: A loom guide bar blade for automatic weaving machinery such as an air or water jet loom wherein the surface of the blade which contacts yarn is nitrided to form a nitrided hardened layer. When this blade is used in automatic high-speed weaving machinery, wearing and the like at contacting points of the blade with the yarn are prevented. As a result yarn fluffing from its being abraded by a roughened blade surface is minimized.

Abstract: The present invention relates to nickel alloy products with their surfaces nitrided and hardened which are formed by pressure casting nickel alloy material, and nitrided and hardened layers are formed in surface layers. Since the nitrided and hardened surfaces of the nickel alloy products according to the invention have much better corrosion resistance than iron products have, anticorrosion treatment such as plating is not required, and rich lubricity and excellent tightening property can be obtained without having seizure and scuffing phenomena.

Abstract: This invention allows the surface of an austenitic stainless steel screw surface to be formed into a hard nitrided layer so as to harden and a part such as a screw head which is in contact with outside air is removed its own ultra hard surface layer in the hard nitrided layer by scouring or the like to be rust preventive. Even if the ultra hard surface layer is thus removed, an inner hard layer in the hard nitrided layer is present beneath the surface layer to be able to maintain a hard state of the screw surface. In the method for manufacturing the austenitic stainless steel screw according to the invention, upon forming said hard nitrided layer on the screw surface by nitriding, the austenitic stainless steel screw surface is cleaned with a fluorine- or fluoride-containing gas prior to nitriding.

Abstract: The surface layer of a hard austenitic stainless steel screw is formed as nitrided layer and then is covered by a plating coat or a resin coat to give properties such as shortening the boring time as well as heightening the surface hardness of the screw itself.

Abstract: Nitrided stainless steel products having a base material of stainless steel containing austenitic stainless steel. At least a portion of the surface layer of the base material is composed of a nitrided hard layer in accordance with the following conditions (A) and (B):(A) the nitrided hard layer substantially does not contain crystalline chromium nitride, and(B) the nitrided hard layer contains from 2 to 12% by weight N atoms.

Abstract: This invention allows the surface of an austenitic stainless steel screw surface to be formed into a hard nitrided layer so as to harden and a part such as a screw head which is in contact with outside air is removed its own ultra hard surface layer in the hard nitrided layer by scouring or the like to be rust preventive. Even if the ultra hard surface layer is thus removed, an inner hard layer in the hard nitrided layer is present beneath the surface layer to be able to maintain a hard state of the screw surface. In the method for manufacturing the austenitic stainless steel screw according to the invention, upon forming said hard nitrided layer on the screw surface by nitriding, the austenitic stainless steel screw surface is cleaned with a fluorine- or fluoride-containing gas prior to nitriding.

Abstract: A hard nitrided layer is formed on austenitic stainless steel by holding the austenitic stainless steel in a heated condition under a fluorine- or fluoride-containing atmosphere and then nitriding it so that a close uniform nitriding layer can be formed, resulting the remarkable improvement in the surface hardness of the above-mentioned austenitic stainless steel. The temperature in the above-mentioned nitriding treatment is set below 450.degree. C. so that high anti-corrosion property, originally inherent in austenitic stainless steel, can be retained without deterioration.

Abstract: An austenitic stainless steel screw having a nitride hard layer on its surface to prevent corrosion on parts of the screw such as a screw head which is in contact with the environment by removing a portion of the nitride hard layer to expose austenitic stainless steel base. By contrast, in the thread part and the like of the screw, the nitride hard layer is retained to improve the hardness and the tapping functions of the screw. In the method for manufacturing, the austenitic stainless steel screw is exposed to a fluorine-or fluoride-containing gas atmosphere prior to nitriding to form a fluoride film on its surface and then is nitrided in that state. Accordingly, the so formed nitride hard layer becomes uniform and deep to obtain an austenitic stainless steel screw having excellent surface properties.

Abstract: This invention relates to a method for forming a uniform, deep nitride layer on and in steel works at low cost, wherein a steel work is fluorided in heated condition in an atmosphere of a mixed gas composed of fluorine gas and inert gas and, then, nitrided in heated condition in an atmosphere of nitriding gas.

Abstract: A method of nitriding nickel alloy comprising steps of holding nickel alloy in an atmosphere of fluorine- or fluoride-containing gas in a heated condition and holding the fluorinated nickel alloy in a nitriding atmosphere in a heated condition to provide the nickel alloy with improved surface hardness by forming a deep uniform nitrided layer on the surface of the nickel alloy.

Abstract: This invention relates to a method of nitriding steel material in a second heat treatment furnace after fluorinating the steel material in a first heat treat furnaceto form a deep and uniform nitrided layer. Then, steel material is treated smoothly by defining the ratio of establishing said both furnaces for fluorinating and niriding on the basis of treating time required for said both treatments since time required for each treatment is different.

Abstract: Steel is nitrided first by treating the steel to be nitrided with NF.sub.3 at elevated temperatures to form a fluorinated layer on the steel, and then the steel is nitrided by heating in a nitriding atmosphere.

Abstract: This invention makes a furnace body divide into two, a pretreating chamber and a nitriding chamber by an opening and closing center wall. After pretreating works to be treated in the pretreating chamber, the opening and closing center wall is opened and the pretreated works are transferred to the nitriding chamber to nitride them. Treatment gas can be saved largely compared with the case that the nitriding is conducted after pretreating works in a furnace which has only a nitriding chamber.

Abstract: This invention relates to a method of nitriding steel material in a second heat treatment furnace after fluorinating the steel material in a first heat treat furnace to form a deep and uniform nitrided layer. Then, steel material is treated smoothly by defining the ratio of establishing said both furnaces for fluorinating and nitriding on the basis of treating time required for said both treatments since time required for each treatment is different.

Abstract: Steel is nitrided first by treating the steel to be nitrided with NF.sub.3 at elevated temperature to form a fluorinated layer on the steel, and then the steel is nitrided by heating in a nitriding atmosphere.