JPH01100217A - Hardening agent - Google Patents

Abstract

PURPOSE:To impart sufficient hardness and uniform physical properties to various steels without causing uneven hardening and abnormal composition by mixing colloidal silica having specified particle diameter in water to prepare the title hardening agent, and using the agent. CONSTITUTION:Colloidal silica having <=1,000mmu particle diameter is mixed in water, or a water-soluble polymer and colloidal silica having <=1,000mmu particle diameter are mixed in water to prepare a hardening agent. The amt. of colloidal silica to be mixed is controlled to about 0.005-50wt.%, based on the whole hardening agent. The mean mol.wt. of the water-soluble polymer is preferably controlled to about 5,000-200,000, and the content of polymer is controlled to about 0.1-50% when used. When the hardening agent is used, the vapor film stage in hardening can be shortened and the cooling rate at the martensite transformation initiating temp. can be reduced.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a quenching agent, and more specifically, it shortens the steam film stage in a quenching operation, controls the cooling rate at around 300°C, and improves quenching properties. The present invention relates to an excellent hardening agent that can impart sufficient hardness and uniform physical properties to the hardening agent.

[Problems to be solved by the prior art and the invention] In general, quenching agents are used to shorten the steam film stage (the stage in which the surface of the workpiece is covered with a steam film) and to improve the cooling rate, especially for steel. It is required that the cooling rate around 300°C, which is the martensitic transformation start temperature, is not too fast.

Water-soluble quenching agents have been widely used due to their high safety, but the problem is that the cooling rate at around 300°C is too fast, resulting in distortion and quenching cracks in the quenched product. There is.

Therefore, in order to control the cooling rate within an appropriate range, attempts have been made to blend a polymer compound such as a water-soluble polymer with water.

However, the hardening agent containing a polymer compound has a
Although the cooling rate near 0°C is moderately controlled, the vapor film stage becomes longer, resulting in an abnormal composition in the metal of the quenched product, as well as insufficient hardness and uneven firing, making it unsatisfactory for practical use. Not Shiuruchino.

[Means for solving problems]

Therefore, the present inventors solved the problems of the above-mentioned conventional technology,
It shortens the steam film stage in the quenching operation and
We have conducted intensive research to develop a hardening agent that can control the cooling rate around 0°C.

As a result, they discovered that the above problems could be achieved by using colloidal silica having a specific particle size,
The present invention has now been completed. That is, the present invention provides a quenching agent characterized by blending colloidal silica with a particle size of 1000 mμ or less in water (hereinafter referred to as the first invention), as well as a water-soluble polymer and a particle size of 1000 mμ or less in water.
The present invention provides a hardening agent (hereinafter referred to as the second invention) characterized in that it contains the following colloidal silica.

In the first invention, colloidal silica is blended with water, but this colloidal silica has a siloxane structure, and each silica particle has a negative charge sufficient to repel each other. be.

There are various methods to produce this colloidal silica, but the most common method is to use an ion exchange resin.
A sodium silicate aqueous solution is passed through a cation exchange resin layer to obtain a sol with a 5ioz/NazO (molar ratio) of 60 to 130, and this is heated and aged at 60°C or higher to polymerize particles of 10 nm or less and have a high density. By growing independently dispersed particles and gradually adding dilute sol obtained through a new ion exchange resin layer, the independently dispersed particles can be polymerized and deposited on the surface to form the desired colloidal silica. . Furthermore, in order to obtain a highly concentrated sol, the sol may be passed through successive layers of anionic and anionic ion exchange resins to achieve high purity.

The colloidal silica used in the first invention has a particle size of 1000
It is less than mμ, preferably 3 to 100 mμ. If it exceeds 1000 mμ, precipitation will occur and it cannot be put to practical use.

In the hardening agent of the first invention, the amount of colloidal silica blended is not particularly limited, but is usually 0.0 of the total amount of the hardening agent.
The amount may be appropriately selected within the range of 0.05 to 50% by weight, preferably 0.01 to 10% by weight.

The quenching agent of the first invention can be obtained by blending the above-mentioned colloidal silica with water, but additives such as rust preventives, preservatives, antifoaming agents, and pH adjusters can also be added. You can also do it.

Further, in the quenching agent of the second invention, a water-soluble polymer is blended with water together with the above-mentioned colloidal silica. Various water-soluble polymers can be used, but those having an average molecular weight of 1 soooo to 200,000 are generally preferred. Specifically, polyvinyl alcohol, polyvinylpyrrolidone, polyisobutylene maleic acid alkali salt (
Na salt.

Suitable examples include alkali salts of polyacrylic acid (Na salt, Ni salt, etc.), polyalkylene glycol, polyoxyethylene-propylene polyether, polyamide polyalkylene glycol, and the like.

In the hardening agent of the second invention, the amount of the colloidal silica and water-soluble polymer blended is not particularly limited, but usually 0.005% of the colloidal silica is added to the total amount of the hardening agent.
-50% by weight, preferably 0.01-10% by weight, and if the water-soluble polymer is appropriately selected in the range of 0.1-50% by weight or 0.5-30% by weight. good.

The quenching agent of the second invention can be obtained by blending water with the above-mentioned water-soluble polymer and colloidal silica, but it can also be obtained by adding a rust preventive agent, a preservative, an antifoaming agent, a pH adjuster, etc. Agents can also be added.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 A water-soluble polymer with a molecular weight of 20% was added to 89.5% by weight of water.
000 polyethylene glycol 10% by weight and particle size 1
A hardening agent was prepared by blending 0.5% by weight of colloidal silica of 2 mμ.

On the other hand, a test piece was prepared by installing a thermocouple at a position of 0.5 mm from the surface of a 5US304 material having a diameter of 10 mm and a length of 30 mm.

Next, this test piece was heated to 800° C., then placed in the above-mentioned quenching agent, and its cooling state was measured.

Fig. 1 shows the cooling curve of the test piece when the liquid temperature of the quenching agent is 40°C, and Fig. 2 shows the cooling curve of the test piece when the liquid temperature of the quenching agent is 60°C.

Comparative Example 1 The same operation as in Example 1 was carried out, except that a quenching agent consisting of 90% by weight of water and 10% by weight of polyalkylene glycol having a molecular weight of 20,000 was used. The results are shown in FIGS. 1 and 2, respectively.

As is clear from a comparison of Example 1 and Comparative Example 1, by adding colloidal silica with a particle size of 12 mμ to the quenching agent, the so-called steam film stage (8
00 to 450°C) almost disappears, and
The cooling rate at around 300'C is the same as that of Example 1 and Comparative Example 1.
It can be seen that the two are about the same.

Moreover, as can be seen from FIG. 1.2, when the liquid temperature of the quenching agent is increased, the time for the vapor film stage becomes longer in Comparative Example 1, but on the other hand, there is almost no difference in Example 1.

〔Effect of the invention〕

As described above, by using the quenching agent of the present invention, the steam film stage in quenching can be shortened, and the cooling rate at the martensitic transformation start temperature of steel can be slowed down. Therefore, if various types of mesh are hardened using the hardening agent of the present invention, sufficient hardness and uniform physical properties can be imparted to the wire without causing uneven hardening or abnormal composition.

Therefore, the quenching agent of the present invention can be effectively used as a heat treatment oil for various metals including quenching steel.

[Brief explanation of the drawing]

Figure 1 shows the cooling curves of the test pieces of the example and comparative example at a quenching agent temperature of 40°C, and Figure 2 shows the cooling curves of the test pieces of the example and comparative example at a quenching agent temperature of 60°C. Show a curve.

Claims (2)

[Claims] (1) A quenching agent characterized by blending colloidal silica with a particle size of 1000 mμ or less in water. (2) A quenching agent characterized by blending water with a water-soluble polymer and colloidal silica with a particle size of 1000 mμ or less.