JPS62256957A - Low-temperature salt bath soft nitriding agent - Google Patents

Abstract

PURPOSE:To obtain a salt bath soft nitriding agent for iron and steel material capable of using at temperatures lower than heretofore, by providing a composition which is composed principally of KOCN containing specific amounts of K2CO3 and to which a compounding material consisting of KCl, LiCl, and BaCl2 is added as an auxiliary component. CONSTITUTION:As the salt bath soft nitriding agent for use in the surface hardening treatment of iron and steel parts, a composition which has KOCN containing <=20wt% K2CO3 as a main active component and to which compounding material of <=450 deg.C melting point consisting of KCl, LiCl, and BaCl>=2 and having a composition indicated by a shaded part in the KCl-LiCl- BaCl2 ternary diagram is added as an auxiliary component is provided. In this way, the low-temp. salt bath soft nitriding agent for surface hardening treatment of iron and steel parts can be obtained at a temp. lower than the conventional treating temp. by about 100 deg.C.

Description

[Detailed Description of the Invention] 3-1 Field of Industrial Application This invention provides surface hardening treatment C for steel materials. The invention relates to a low temperature salt bath soft nitriding agent that can sufficiently harden.

3-2 Conventional technology Surface hardening treatment of steel materials today? The salt bath nitrocarburizing agent that is commonly used has alkali cyanate as the main active ingredient, and C: alkali carbonate, alkali cyanide, and alkali chloride. It consists of two or more mixed inorganic salts and ancillary ingredients. However, the main active ingredient is sodium cyanate or potassium cyanate in a salt bath melted at 5620°C using a mixed salt containing about 20 to 70% by weight. The surface of the steel material was hardened by immersing the steel material as a product.

3-3 Problems to be Solved by the Invention The processing time for surface hardening of steel materials using a salt bath nitrocarburizing agent as described above generally depends on the type of steel material being treated and the necessary hardening depth. cannot be selected, but usually, in most cases,
Regarding the processing temperature, it is said that around 550° C. is appropriate in the conventional method. However, it is unclear whether such treatment temperatures are still appropriate even today, and whether there is any room for improvement in the conventional hardening agents required for hardening treatment, and whether the deformation of steel materials due to hardening treatment can be improved. Is it possible to suppress or reduce it? Furthermore, are there any unnecessary expenses for utilities during the hardening treatment of steel materials?
When considering conventional methods in general, it is highly questionable whether these methods will be followed, and there are problems that need to be improved.

3-4 Means for the invention to solve the problem This invention aims to correct the above-mentioned difficulties by combining
Potassium cyanate containing 0% or less potassium carbonate is the main active ingredient, and by adding as an auxiliary ingredient a compounding agent consisting of potassium chloride, lytecum chloride, and barium chloride with a contact point of 450°C or less, A low-temperature salt bath softener that lowers the processing temperature by approximately 100 degrees Celsius from conventional processing temperatures, which not only allows for significant savings in utility costs, but also significantly suppresses the deformation of steel materials caused by hardening treatment. It is intended to provide a nitriding agent.

3-5 Examples Hereinafter, examples of the present invention will be described.1 Weight ratio: 20%
Potassium cyanate containing the following potassium carbonate is used as the main active ingredient when hardening the surface of steel materials, and this potassium cyanate is composed of three components of potassium chloride, lytecum chloride and barium chloride as auxiliary components.The melting point is 450.
A low-temperature salt bath nitrocarburizing agent can be obtained by adding a compounding agent at a temperature below ℃. However, the reason why the above-mentioned potassium carbonate is specified to be 20% or less by weight is that the melting point of potassium cyanate as the main active ingredient is set to 430°C or less, thereby reducing the processing temperature during surface hardening treatment of steel materials. The aim is to reduce the temperature by 100'' (:) compared to the conventional method as mentioned above.In addition, the compounding agent as the auxiliary component is That is, the melting points of the salt bath agent, potassium chloride, t-cum chloride and barium chloride obtained under the compounding ratio in Example 1 described later in the drawings are 774°C and 605°C, respectively.
In the triangle with the apex at 955°C, the melting point at the time of mutual melting of potassium chloride and litecum chloride (;
At 48℃, the ratio of lytecum chloride and barium chloride is 512
℃, 6 for Bacll and 2Kcl・Bacll
50°C and 2Kcl-Bacl.

The temperature between Kcl and Kcl is 658°C, and when these kings are melted together to form a compound, it is necessary that the temperature is within the range of conditions that satisfy all of the melting points of each of the above. Therefore, the shaded area shown below is selected as the temperature range that meets condition C2.

Although potassium cyanate containing 20% or less of potassium carbonate by weight is used as the main active ingredient, the increase in melting point is suppressed by the presence of the auxiliary ingredient, so the treatment temperature during surface hardening of steel materials is lowered. 420℃~4
It is understood that there is a range C2 of 30°C. That is, it has been found that surface hardening can be performed at a temperature of approximately 100° C. compared to approximately 550° C., which is the treatment temperature for surface hardening steel materials using conventional salt bath soft-nitriding agents. Therefore, by lowering the processing temperature, it is possible to not only save on utility costs, but also to significantly suppress the deformation of steel materials during heat treatment, making it possible to produce steel products with good surface hardening without cracks or distortions at a lower cost than with conventional processing methods. It has the characteristics that can be obtained.

Next, as Example 1 of the blending ratio, the weight ratio of each component (2) is shown in (H).

Example I KoCN 74. a, Co, 5.01 KCI 9. O1t LiC17,5# BaC113,9z Surface hardness (micro Vickers hardness) when the following various steel materials were immersed at 450°C for 3 hours in a salt bath agent obtained with the above blending ratio. 14MV1009
), as well as the salt bath agent (H
If you compare and display the MV, it will look like this:

As Example 2 of the blending ratio, the weight ratio of each component is shown in the table below.

Example 2 KoeN 64.9 mold part chi, Co, 161z KCI 8.71 LiC15,8# BaC1x 4.51 The same material as in Example 1 was added to the salt bath agent obtained with the above blending ratio. Surface hardness when immersed at 450℃ for 5 hours) (Displaying MVloog) Comparison and display of HMV of the same material treated with conventional salt bath side immersion at 540℃ for 5 hours Then it will look like this:

As can be understood from the above two examples, 1. The surface hardness of the steel material surface hardened with the salt bath agent according to the present invention, HMVl
Regardless of the lower processing temperature (90 degrees lower in this case), the same effect can be achieved as the surface hardness achieved by the conventional method, that is, approximately the same surface hardness can be obtained. found.

[Brief explanation of drawings]

The drawing is a ternary melt phase diagram of the auxiliary components. May 1, 1985

Claims (1)

[Claims] (1) Potassium cyanate containing potassium carbonate at a weight ratio of 20% or less is the main active ingredient, and a compounding agent with a melting point of 450°C or less consisting of potassium chloride, lithium chloride, and barium chloride is used as an auxiliary ingredient. Low-temperature salt bath soft nitriding agent characterized by the addition of