JPS6299455A - Salt bath soft nitriding method - Google Patents

Abstract

PURPOSE:To avert the formation of an alkali cyanurate in a salt bath consisting of an inorg. salt mixture composed of >=2 among alkali cyanate, alkali carbonate, alkali cyanide and alkali chloride in the title method using the above- mentioned salt bath by maintaining the humidity of the air, etc. to be blown to zero %. CONSTITUTION:Surface treatment of irons and steels is executed by using the salt bath agent consisting of the inorg. salt mixture composed of >=2 among alkali cyanate, alkali carbonate as an auxiliary component, alkali cyanide and alkali chloride as working components. The iron and steel parts to be treated are immersed into the above-mentioned salt bath and are held therein while the air of 0% humidity or the gas of the same effect is blown thereto in the molten state of the above-mentioned salt bath agent. The reaction between the moisture contained in the gas such as air to be blown and the alkali cyanate as expressed by the formula is thereby obviated and the formation of the alkali cyanurate in the bath is obviated. There is, therefore, no possibility of infringing upon Patent 1061359.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a salt bath nitrocarburizing method.

(Prior Art) The salt bath nitrocarburizing method that has been most widely and almost exclusively practiced in Japan is a method called the Tuff Try 1 method. This method uses a mixed inorganic salt consisting of alkali cyanate () as an active ingredient and alkali carbonate and alkali cyanide as auxiliary ingredients.
This is a salt bath nitrocarburizing method in which treated steel parts are kept immersed in a bath kept melted at ~570°C while blowing air at room temperature.

(Problems to be Solved by the Invention) However, in such a conventional salt bath nitrocarburizing method, the alkali cyanate, which is an active ingredient, has a
At a high temperature of 570°C, it reacts with the moisture contained in the blown air as shown in the following formula, producing an alkali salt of cyanuric acid in the salt bath, and over a considerable period of time, a considerable amount of cyanuric acid is formed. It has now been determined that this can be achieved.

4 KOCN +311□0 → KzCO3+ 2/3 (KJ3C3hh) + Co
□ +Nth Therefore, it is recognized that the nitrocarburizing method using this method conflicts with Patent No. 1061359 after being implemented for a certain period of time.

(Means for Solving the Problems) The purpose of the present invention is to provide a soft nitriding method that does not conflict with the Patent No. 1061359, and can also be called an improvement on the tuftride method.

That is, the method of the present invention uses a salt bath agent consisting of alkali cyanate as an active ingredient and two or more mixed inorganic salts selected from alkali carbonate, alkali cyanide, and alkali chloride as auxiliary ingredients. When performing surface hardening, a salt bath characterized in that the steel parts to be treated are maintained infiltrated into the salt bath agent while blowing air with a humidity of 0% or a gas having the same effect in the molten 4Je state of the salt bath agent. This is a soft nitriding method.

(Example) Next, the present invention will be explained by examples.

KOCN in a steel pot with a diameter of 60 cm and a depth of 100 cm.
32X, Na2CO323% and NaCN 45χ
A salt bath agent consisting of was charged, heated and melted and maintained at 570°C. Thereafter, a cleaning tank containing an appropriate dehydrating agent was used, and air dried to a humidity of 0 degrees was divided into small pieces by a nozzle and blown into the nitriding tank from the bottom at a rate of 7,000 rpm per hour, and the steel parts were immersed in the nitriding tank. In this way, it was possible to achieve an extremely uniform finish.

The advantage of this method is that the finished surface is not affected by moisture in the outside air and can be finished evenly and beautifully.
Furthermore, the invention must not infringe on the patent specified in n;1.

Note that, as in the conventional tuftride method, if normal air with a humidity of 75χ and a temperature of 20°C is blown without drying to 0χ, it is calculated that at least about 1601 of heated water vapor is blown into the air 7001. Therefore, 38.6 g of alkali cyanurate would be produced in the bath, potentially infringing the patent.

Further, in the method of the present invention, a dehydrating agent such as concentrated sulfuric acid, phosphoric anhydride, or calcium oxide (in this case, blowing of carbon dioxide gas is not used) may be used as the desiccant. By the way, the salt bath agent used in the examples, Patent No. 1
This is shown as one of the representative examples of the tuftride method described in No. 08969.

Claims (1)

[Claims] When surface hardening of steel is carried out using a salt bath agent consisting of an alkali cyanate as an active ingredient and a mixed inorganic salt of two or more selected from alkali carbonate, alkali cyanide, and alkali chloride as an auxiliary ingredient, the salt bath A salt bath nitrocarburizing method characterized in that a steel part to be treated is maintained immersed in the salt bath agent while blowing air with a humidity of 0% or a gas having the same effect into the molten state of the agent.