JP3105975B2 - Glossy chemical polishing treatment liquid for hardened steel members and chemical polishing treatment method for the material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glossy chemical polishing solution for hardened steel members and a method for chemical polishing of the material. More specifically, the present invention relates to a method for forming complicated shapes such as carburized gears used in transmissions and differentials. The present invention relates to a glossy chemical polishing treatment liquid suitable for glossy polishing of a hardened steel member such as a quenched steel material, and a chemical polishing treatment method for the material.

[0002]

2. Description of the Related Art Conventionally, steel members requiring high strength, such as transmission gears of automobiles, have been subjected to a heat treatment such as a quenching treatment, particularly a carburizing quenching treatment, and have been put to practical use.

[0003] Such carburized and hardened steel members include:
An incompletely quenched layer called an abnormal layer exists over 5 to 50 μm from the surface. This abnormal layer has a lower hardness than the normal quenched layer existing immediately below it, and acts to reduce the compressive residual stress at the outermost surface, thus causing a reduction in fatigue strength. Further, even in a hardened steel material in which such an abnormal layer does not exist, if the surface roughness is large, this also causes a reduction in fatigue strength.

[0004] As a method of solving these problems of the prior art, as a method of manufacturing a high-strength gear, a surface hardening treatment is performed, then shot peening is performed, and a finish cutting is performed by grinding with a cubic boron nitride wheel. A mechanical polishing method such as that disclosed in Japanese Unexamined Patent Publication No. Hei 1-264727) has been proposed.

[0005] As another method other than the above, an "electrolytic polishing method for gears" in which an electropolishing liquid is sprayed toward the tooth bottom of a gear to be polished and the tooth bottom is etched (Japanese Patent Laid-Open No. Sho 62-2).
No. 4000: Japanese Unexamined Patent Publication No. 2-129421,
An electrolytic polishing method such as disclosed in JP-A-2-129422 has been attempted.

[0006] As a chemical polishing method for steel, "iron,
Chemical gloss treatment of zinc or their alloys "(US Pat. No. 3,369,914). This method is characterized in that an aqueous solution having a molar ratio of hydrogen peroxide to hydrofluoric acid of 3 to 7 is used as a treatment liquid, and it is described that a glossy surface can be obtained by immersion treatment for about 1 minute.

[0007]

However, in the mechanical polishing method disclosed in Japanese Patent Application Laid-Open No. 1-264727, the working efficiency is low because the hardness of the hardened steel material is high, and especially the shape of gears and the like is complicated. In the case of a part, there is a problem that if the vicinity of the tooth bottom where improvement in fatigue strength is a problem is to be precisely polished, the processing efficiency is significantly reduced.

In the electropolishing method proposed in Japanese Patent Application Laid-Open No. 62-24000, if this method is applied to actual machine parts, in order to ensure processing accuracy, the arrangement of the counter electrode and the like must be changed. It needs to be finely changed every time, and there is a problem that a very complicated device is required.

In addition, the chemical gloss treatment disclosed in US Pat. No. 3,369,914 is a method for plating undercoating that does not matter the polishing rate or polishing amount, or an improvement in corrosion resistance.
Alternatively, the present invention can be applied to the use of gloss processing. However, when this method is applied to a polishing process such as a precision polishing process for a part requiring strict dimensional accuracy such as a hardened gear, a method of applying the polishing process and necessary conditions are not disclosed. However, those skilled in the art cannot apply the conventional chemical polishing method to the processing of parts, especially the polishing method. Further, since the composition of the polishing liquid has a large molar ratio of hydrogen peroxide to hydrofluoric acid of 3 to 7, decomposition of hydrogen peroxide is apt to occur when the liquid is left, and as a result, expensive hydrogen peroxide is wasted. In addition, there is a problem that it is difficult to perform polishing on an industrial scale from the viewpoint of the stability of the polishing liquid.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems of the prior art, and have conducted various systematic experiments. As a result, the present invention has been accomplished.

(Object of the Invention) An object of the present invention is to provide a glossy chemical polishing solution suitable for glossy polishing of a hardened steel member such as a hardened steel having a complicated shape. Another object of the present invention is to provide a glossy chemical polishing solution for hardened steel members that can be processed simply, with high precision and with high efficiency without requiring special equipment.

An object of the present invention is to provide a method for glossy chemical polishing of a hardened steel member capable of performing simple, high-precision and high-efficiency processing of a hardened steel material having a complicated shape without requiring special equipment. To be.

The present inventors have focused on the following with respect to the above-mentioned problems of the prior art. That is, first, attention was paid to a chemical polishing treatment solution as a means for overcoming the above-mentioned problems of the mechanical polishing method and the electrolytic polishing method, which are the conventional techniques.

Therefore, the surface of a hardened steel material having a complicated shape is formed only by immersing the surface of the special composition in the chemical polishing liquid by utilizing the strong chemical dissolving action and the smoothing action of the chemical polishing liquid having the special composition. Along with enabling high-precision polishing processing, simplification of equipment, improvement of processing efficiency and improvement of polishing quality were realized.

[0015]

[Means for Solving the Problems]

(First Invention) The glossy chemical polishing solution for hardened steel members of the first invention is a glossy chemical polishing solution for hardened steel members having a concentration of 0.2 to 2 mol / l. Acid and concentration
0.4 to 4 mol / l of hydrogen peroxide, and the molar ratio of the hydrofluoric acid to the hydrogen peroxide is 1: 1.5 to 2.8.
It is characterized by being.

(Second Invention) The glossy chemical polishing treatment method for a hardened steel member according to the second invention comprises a step of hardening the steel member, a hydrofluoric acid having a concentration of 0.2 to 2 mol / l and a concentration of 0.2 mol / l. 4-4 mol / l
Chemically polishing the hardened steel member in a bright chemical polishing treatment solution comprising a hydrofluoric acid and a hydrogen peroxide at a molar ratio of 1: 1.5 to 2.8. And characterized by the following.

[0018]

[Action]

The mechanism by which the glossy chemical polishing treatment liquid for hardened steel members of the first invention and the method for glossy chemical polishing treatment of the hardened steel members of the second invention exhibit excellent effects is not necessarily clear yet, but is as follows. It is thought to be.

(Function of the First Invention) The bright chemical polishing solution for hardened steel members of the present invention has a hydrofluoric acid concentration of 0.2 to 2 mol / l and a hydrofluoric acid concentration of 0.4 to 4 mol / l. Consisting of hydrogen oxide,
And the ratio of the concentration of the hydrofluoric acid to the hydrogen peroxide is 1: 1:
1.5 to 2.8. According to the electrochemical model when the metal dissolves in the acid, in a hydrofluoric acid solution in which hydrogen peroxide coexists, hydrogen peroxide causes a catalytic decomposition reaction at the contact surface with the material to be treated, and the generated nascent oxygen Exerts a strong oxidizing power, and it is considered that so-called transpassive dissolution proceeds on the treated surface. In this overpassive dissolution, uneven dissolution based on the metal structure and the like on the treated surface is prevented, and a glossy surface appears. At this time, the formation of perpassivation strongly depends on the dissolving power of hydrofluoric acid and the oxidizing power of hydrogen peroxide, and is stable in a range of the molar ratio of hydrofluoric acid to aqueous hydrogen peroxide of 1: 1.5 to 2.8. It is considered that the above-mentioned glossy surface can be obtained because the excessive passivation is maintained. As described above, due to the chemical dissolving action of the chemical polishing solution having the above-described configuration, uniform polishing can be performed regardless of the shape on the surface of the material to be processed, which is made of a hardened steel member such as a quenched steel material, in contact with the polishing solution. proceed. Also, since the hydrogen peroxide in the chemical polishing treatment solution has an appropriate concentration and the molar ratio of hydrofluoric acid to hydrogen peroxide is appropriate, it is possible to obtain a stable glossy surface on the surface of the material to be processed. Besides, the hardened steel material can be polished at a practical speed regardless of the hardness of the material to be processed. Furthermore, since the concentration of hydrofluoric acid in the chemical polishing treatment liquid has an appropriate concentration, the polishing rate can be controlled to a required rate.

The reasons for limiting the numerical values of the concentrations of hydrofluoric acid and hydrogen peroxide and the ratio of the concentrations of hydrofluoric acid and hydrogen peroxide will now be described.

The concentration of hydrofluoric acid is 0.2 to 2 mol / l. The concentration of hydrofluoric acid affects the polishing rate together with the bath temperature. When the temperature of the processing solution is constant, the polishing rate increases as the concentration of hydrofluoric acid increases, but at the same time, the polishing temperature increases sharply due to the heat of reaction, and the polishing rate further increases.
If it exceeds ol / l, it becomes difficult to maintain and control the polishing rate. On the other hand, if it is less than 0.2 mol / l, the polishing rate is 1 μm / min or less, and the efficiency is poor. Industrially, the polishing rate is desirably 1 to 100 μm / min, and 0.2 to 2 mol / l is selected as the concentration of hydrofluoric acid that achieves this polishing rate.

The concentration of hydrogen peroxide is 0.4 to 4 mol / l. This is because when the concentration is less than 0.4 mol / l, the gloss is reduced, and when the concentration is more than 4 mol / l, the decomposition action due to the heat of reaction becomes severe and the control of the treatment liquid becomes difficult. . By adjusting the concentration to 0.4 to 4 mol / l, a glossy surface can be stably obtained. Note that the concentration is mainly determined in the above range in relation to the concentration of the hydrofluoric acid.

The ratio of the concentration of hydrofluoric acid to the concentration of hydrogen peroxide is 1: 1.5 to 2.8 in molar ratio. If the molar ratio is less than 1.5, the treated surface of the material to be treated lacks gloss, that is, microscopic smoothing becomes insufficient. If the molar ratio exceeds 2.8, the gloss does not decrease, but there is no advantage in this region, expensive hydrogen peroxide is wasted, and the bath composition tends to fluctuate. By setting the molar ratio to 1: 1.5 to 2.8, gloss polishing can be performed at a practical speed.

(Function of the Second Invention) The glossy chemical polishing treatment method for a hardened steel member of the present invention specifies a specific concentration of hydrofluoric acid and a specific concentration of hydrogen peroxide in a steel material subjected to a hardening treatment such as quenching. This is a method in which a chemical polishing treatment is performed by immersion in a chemical polishing treatment solution adjusted to a molar ratio. As a result, due to the chemical dissolving action of the specially configured chemical polishing solution, uniform polishing proceeds irrespective of the shape on the surface of the material to be processed made of the steel in contact with the polishing solution. In addition, since the hydrogen peroxide in the chemical polishing treatment solution has an appropriate concentration and the molar ratio between hydrofluoric acid and hydrogen peroxide is appropriate, it is possible to stably obtain a glossy surface on the surface of the workpiece. Besides, it is possible to polish a hardened steel member such as a hardened steel material at a practical speed irrespective of the hardness of the material to be processed. Further, in the method of the present invention, since the concentration of hydrofluoric acid in the chemical polishing treatment liquid has an appropriate concentration, the polishing rate can be controlled to a required rate.
As described above, the polishing efficiency of a hard hardened steel member such as a hardened steel material can be improved. The reasons for limiting the numerical values of the concentration of hydrofluoric acid and hydrogen peroxide and the ratio of the concentration of hydrofluoric acid to hydrogen peroxide in the chemical polishing treatment liquid are as described in the description of the operation of the first invention.

[0026]

【The invention's effect】

(Effect of the First Invention) The glossy chemical polishing solution for hardened steel members of the first invention can stably form a glossy surface on the contact surface of a hardened steel member such as a quenched steel material, and can perform the treatment. The hardened steel material can be polished at a practical speed regardless of the hardness of the object. In addition, uniform polishing can be performed regardless of the shape of the material to be processed.

(Effect of the Second Invention) The glossy chemical polishing method for hardened steel members according to the second invention enables simple, high-precision and high-efficiency hardening of a hardened steel material having a complicated shape without the need for a special device. Can be processed. As a result, in a carburized and quenched gear or the like, the abnormal carburized layer is removed, the surface roughness is reduced, and the fatigue strength can be significantly improved. Furthermore, since the surface has a gloss finish, the commercial value of the appearance is improved, and the electrochemical non-uniformity of the surface is reduced, so that the resistance to rust generation is improved.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first and second aspects of the present invention will be described below in more detail with reference to specific examples (the second aspect will be described.

First, a specific example of the first invention (first specific example)
The glossy chemical polishing solution for hardened steel members is described below.

In the glossy chemical polishing solution for hardened steel members of the first specific example, hydrofluoric acid plays a role of chemically dissolving and removing the surface of the steel material by first acting as a normal acid. Generally, the chemical polishing liquid is composed of an acid and an oxidizing agent. In the present invention, hydrofluoric acid is used as the acid because Fe ions eluted by polishing are stabilized in the bath as complex ions such as FeF ₆ ^3- . As a result, spontaneous decomposition of hydrogen peroxide due to the catalytic action of Fe ions is suppressed, and treatment on an industrial scale becomes possible.

The hydrofluoric acid used in the first specific example may be either hydrofluoric anhydride (99% or more) or dilute hydrofluoric acid. From the viewpoint of easiness of the treatment, dilute hydrofluoric acid having a concentration of about 50% is preferable. The concentration of hydrofluoric acid used in the first invention is 0.2 to 2 mol / l. In this specific example, the concentration of the hydrofluoric acid is preferably from 0.3 mol / l to 1.5 mol / l. By setting the content within the above range, a sufficient polishing rate of about 2 to 50 μm / min is obtained, though it varies depending on the processing temperature, and the polishing rate can be easily maintained and controlled.

Hydrogen peroxide is an oxidizing agent that promotes the dissolution of Fe and also makes the chemically polished surface glossy, that is, microscopically smooth. In the first specific example, the reason why hydrogen peroxide was used as the oxidizing agent is that, in addition to its strong oxidizing power, products after the treatment are water (H ₂ O) and oxygen gas (O ₂ ). . As a result, it is easy to perform the treatment for a long time without the obstructive effect of the product, and it is very convenient also in the treatment of the waste liquid. The type of the hydrogen peroxide is not particularly limited, but 30 to 60% aqueous hydrogen peroxide which is generally available as an industrial chemical is preferable.

The concentration of the aqueous hydrogen peroxide is 0.6 to 0.6.
Preferably it is 3.0 mol / l. This means that the concentration
When the amount is 0.6 mol / l or more, a sufficient glossy surface can be stably obtained, which is preferable. The concentration is 3.0 m
When the amount is not more than ol / l, it is preferable because decomposition by reaction heat hardly occurs. By setting the concentration range to be within the range of 0.6 to 3.0 mol / l, a particular effect can be exhibited in that the compound can be used more stably, particularly when used for a long time by continuous treatment. it can.

The glossy chemical polishing solution of the present embodiment comprises the hydrofluoric acid as an acid, the hydrogen peroxide as an oxidizing agent,
Further, it is made of an appropriate combination of water and additives as required, and enables gloss polishing at a practical speed.

Here, the ratio of the concentration of hydrofluoric acid to the concentration of hydrogen peroxide is preferably from 1: 1.6 to 2.4 in molar ratio. When the molar ratio is 1.6 or more, a clearer glossy surface can be obtained. In the case of continuous processing, a sufficient glossy surface can be obtained even if the density fluctuates when replenishing consumables.
When the molar ratio is 2.4 or less, the composition fluctuation of the processing solution can be further suppressed, and waste of expensive hydrogen peroxide can be prevented.

Next, a specific example of the second invention (second specific example)
The glossy chemical polishing treatment method for the hardened steel member will be described below.

The second invention and the second specific example correspond to the first embodiment.
The present invention relates to a method for performing a gloss chemical polishing treatment of a steel member using the gloss chemical polishing treatment solution for hardened steel members of the invention or the first specific example.

In the gloss chemical polishing method for a hardened steel member according to the second embodiment, first, a steel member is hardened (a steel member hardening process). In this step, a steel member as a material to be treated is subjected to a hardening treatment by a method such as carburizing and quenching, induction quenching, and flame quenching. Note that a material that has been subjected to a curing treatment in advance may be used, or a material that has been subjected to a normal tempering treatment after a treatment such as a quenching treatment may be used. However, in terms of metallographic structure, it is preferable that most of the fabric has a so-called martensite structure.

As the steel type of the steel member, any steel type, such as carbon steel, chromium steel and nickel-chromium-molybdenum steel, can be used as long as it can be easily dissolved in an acid. However, the application of the present invention is difficult for some steel types, such as stainless steel, which have extremely high acid resistance, since chemical dissolution does not substantially proceed. Further, in a steel material in which precipitated particles such as various carbides stable to an acid are present in the dough, it is preferable that the precipitated particle diameter is small.

The shape of the steel material may be any shape, but when immersed in the polishing treatment liquid of the present embodiment, the desired portion to be polished comes into sufficient contact with the liquid and can be subjected to the stirring action of the liquid. It is desirable that the shape and structure be used. Therefore,
It is preferable that the portion to be polished does not have an extremely narrow gap or a bag portion. When the steel material does not have such a suitable shape and structure, it is preferable that the processing atmosphere be in an active state, for example, by supplying a jet of a polishing liquid to a desired polishing portion.

Next, the hardened steel member is chemically polished in a glossy chemical polishing solution (chemical polishing process). here,
As the gloss chemical polishing treatment liquid, the treatment liquid described in the first invention or the first embodiment is used. That is, the concentration is 0.2 to 2 mol
/ L hydrofluoric acid and a concentration of 0.4 to 4 mol / l hydrogen peroxide and a molar ratio of the hydrofluoric acid to the hydrogen peroxide of 1: 1.5 to 2.8. Liquid. Or
Hydrofluoric acid with a concentration of 0.3 to 1.5 mol / l and a concentration of 0.6 to 3 m
ol / l of hydrogen peroxide, and a treatment liquid having a molar ratio of the hydrofluoric acid to the hydrogen peroxide of 1: 1.6 to 2.4 is preferable. The hydrofluoric acid, hydrogen peroxide, their concentrations, and the ratio of the concentrations are as described in the first invention or the first specific example.

Next, a specific example of the gloss polishing treatment method for the hardened steel member of this embodiment will be briefly described as follows. That is, first, a gloss polishing treatment liquid used in the present method is prepared. The polishing liquid is prepared as an aqueous solution containing hydrofluoric acid and hydrogen peroxide at a predetermined molar concentration. The adjusting method is not particularly limited, but usually the easiest method is to measure a predetermined amount of dilute hydrofluoric acid and hydrogen peroxide solution as industrial chemicals by a gravimetric method or a volumetric method, Are mixed, and further, insufficient water is added thereto to obtain an aqueous solution having a predetermined concentration. The chemical used and the water for dilution do not hinder the treatment unless the impurities are particularly large. However, it is preferable to use the first-grade reagent or more and the ion-exchanged water as the chemical.

In the gloss chemical polishing method of the second embodiment, if the hardened steel member is in a clean state, it may be subjected to chemical polishing immediately. Dirt such as oil is attached to the hardened steel member, and in such a case, it is preferable to perform a cleaning process for removing the dirt before starting the chemical polishing process. As the cleaning treatment, a method used in ordinary cleaning treatment, such as cleaning with an organic solvent or an alkaline cleaning liquid, can be applied. Also,
In the case of quenched steel with oxide scale etc. on the surface,
It is not necessary to remove the oxide scale unless it is an extremely thick film. However, if the oxide scale is thick and extremely strongly adhered, a method such as a mechanical forced peeling method such as shot blasting or an acid etching method is used. It is preferable to remove them.

The hardened steel member, such as a quenched steel material, which has been subjected to pretreatment as required, is immersed in the treatment liquid according to the first invention or the first embodiment adjusted to a predetermined concentration. Since this process proceeds with the generation of oxygen gas, the natural stirring effect of the generated gas is large, and it is not necessary to add a stirring means. The bath temperature tends to increase due to the heat of reaction accompanying the progress of the process, but the increase in the bath temperature is accompanied by an increase in the polishing rate. preferable. After being immersed in this manner for a predetermined time, that is, until a desired polishing amount is obtained, pulling, washing, and drying are performed. At this time, the treated surface may be discolored to a rust color, which may be inconvenient depending on the purpose of use. In this case, before the washing step, post-acid washing with a thin acid, specifically, about 2 to 3% hydrochloric acid or the like is performed. The problem can be solved by adding a step and further an alkali neutralization step.

The glossy chemical polishing method of this embodiment can be widely applied to polishing of hardened steel members such as general hardened steel parts, and particularly, the conventional mechanical polishing method or electrolytic polishing method can be applied. Demonstrates its power in polishing difficult parts with complicated shapes.For example, in automotive-related parts, it is effectively used for applications such as improvement of fatigue strength of various gears, bearings, springs, etc. or improvement of friction and wear characteristics. be able to.

The gloss chemical polishing method for the hardened steel member of the present embodiment, which is particularly preferable when the chemical polishing processing is performed continuously and / or in large quantities, will be described below.

That is, in the chemical polishing step, after the material to be processed is subjected to gloss chemical polishing with a chemical polishing treatment liquid having a relatively high concentration (high), the concentration is further reduced (low).
This is a glossy chemical polishing treatment method for a hardened steel member treated with a chemical polishing treatment liquid.

After being treated with a high concentration chemical polishing treatment solution,
If water is washed after a lapse of a predetermined time, the reaction may proceed due to the high-concentration processing liquid adhering to the surface of the material to be processed, and the gloss may decrease. By performing the two-stage chemical polishing process in this way, that is, by reprocessing with a low-concentration processing solution,
The gloss reduced by the progress of the reaction can be recovered. Further, after the treatment, the reaction of the surface of the material to be treated with the adhesion treatment liquid does not proceed so much during the holding until the washing with water, so that a more excellent glossy surface can be exhibited. Therefore, this method is particularly suitable when a chemical polishing treatment is performed continuously and / or in a large amount.

The method further comprises a step of hardening the steel member, hydrofluoric acid having a molar concentration of 0.8 to 1.5 mol / l, and hydrogen peroxide having a molar concentration of 1.6 to 3.0 mol / l. A first chemical polishing treatment step of chemically polishing the hardened steel member with a chemical polishing treatment liquid having a high molar ratio of an acid to the hydrogen peroxide of 1: 1.6 to 2.4, and a molar concentration of 0.2 to 0.8 m
ol / l hydrofluoric acid and a hydrogen peroxide having a molar concentration of 0.4 to 1.6 mol / l, and a chemical polishing treatment with a low concentration of the hydrofluoric acid and the hydrogen peroxide of 1: 1.5 to 2.8. It is preferable that the method comprises a second chemical polishing treatment step of chemically polishing the hardened steel member subjected to the primary chemical polishing treatment with a liquid.

An embodiment of the present invention will be described below.

First Embodiment Material to be treated made of JIS SCr 420H chrome steel (size: 15
mm × 10 mm × 50 mm). The surface is 3 by cutting
It was ~4μR _z finish. Next, this material to be treated is shown in Table 1.
Carburizing and quenching were performed under the conditions shown in Table 1 to obtain polished samples.

[0052]

[Table 1]

Next, a commercially available reagent 47% hydrofluoric acid, 3%
Using 0% hydrogen peroxide solution and ion-exchanged water, the components were mixed to have the composition shown in Table 2 to prepare 500 ml of a chemical polishing solution.

[0054]

[Table 2]

Next, the prepared polishing sample was degreased with an alkaline degreasing solution, immersed in each polishing solution maintained at the temperature shown in Table 2, and subjected to a treatment for 2 minutes. Subsequently, washing, draining, and drying were performed, the presence or absence of surface gloss and the polishing depth were measured, and the polishing rate was calculated. Table 2 shows the results.

For comparison, chemical polishing was performed under the same conditions as in this example except that the composition of the processing solution was different, and the same performance evaluation was performed (sample numbers C1 to C).
6). The results are shown in Table 3.

[0057]

[Table 3]

As is clear from Tables 2 and 3, the concentration of hydrofluoric acid is 0.2 to 2 mol / l and the concentration of hydrogen peroxide is 0.4 to 4 mol / l.
l, and the molar ratio of hydrofluoric acid to hydrogen peroxide is 1: 1.5 to
Sample Nos. 1 to 1 polished with a processing solution having a composition of 2.8
In the case of this example of 0, the surface was glossy in all cases, and the polishing rate had a value of 1.2 to 98.5 μm / min.
On the other hand, the comparative sample C1 had no surface gloss, and together with the sample number C2, the polishing rate was as low as 1 μm / min or less. In sample C3, the polishing rate was extremely high, and the polishing process could not be controlled. In addition, sample number C4
And C5, the surface was matte with no gloss. Further, in sample No. C6, the same values were obtained for both the polishing rate and the surface gloss as in this example, but the treatment liquid was severely decomposed, and the polishing rate was significantly reduced accordingly.

Second Embodiment

Round bars (15 mmφ, length 100 mm) of JIS SCM420H chromium-molybdenum steel (sample No. 11) and SNCM420H nickel-chromium-molybdenum steel (sample No. 12)
And carburized and quenched under the conditions shown in Table 1 in the same manner as in the first embodiment. Also, providing a similar dimension JIS S55C carbon steel (Sample No. 13), the frequency 150KH _Z
, An induction hardening treatment with an effective hardening depth of 1 to 2 mm was performed. Next, these three types of quenched steels have a surface roughness of 4 μR.
Grinding processing was performed to about _z to obtain a polished sample.

Next, hydrofluoric acid 1 mol / l, hydrogen peroxide 2 m
ol / l, a chemical polishing treatment liquid having a molar ratio of hydrofluoric acid to hydrogen peroxide of 1: 2.0 was prepared.

Next, the polished sample was degreased with alkali, and then immersed in the above-mentioned chemical polishing treatment liquid kept at 40 ° C.
For a minute.

The surface of each of the obtained polished samples had a mirror-like gloss. Then, for this polishing sample,
The polishing depth, polishing rate and surface roughness were measured. Table 4 shows the results.

[0064]

[Table 4]

As is evident from Table 4, the surface roughness was significantly improved by the chemical polishing treatment for 3 minutes, and the polishing depth, that is, the polishing rate, was almost the same regardless of the type of the sample. It was confirmed that the processing was highly efficient.

Third Embodiment

A JIS SCr420H chrome steel gear (module: 2.75, pitch circle radius: 85 mm, number of teeth: 28) was prepared and carburized and quenched under the conditions shown in Table 1 in the same manner as in the first embodiment. . Next, a chemical polishing treatment liquid similar to that used in the second embodiment was prepared, the gear was immersed at a treatment temperature of 40 ° C., and a polishing treatment was performed for 2 minutes and 30 seconds. As a result, the polished portion had a bright finish. Next, the change in the dimension of the gear, that is, the polishing depth, was measured at each of the tooth root, the tooth center, and the tooth tip. Table 5 shows the obtained results.
Shown in

[0068]

[Table 5]

As is clear from Table 5, the polishing depths of the root, the center of the tooth, and the tooth tip are almost the same, and high precision polishing can be performed even on a hardened steel material having such a complicated shape. Was confirmed.

Fourth Embodiment

Using the same material to be processed as in the first embodiment,
Similarly, carburizing and quenching were performed to obtain a polished sample (sample No. 1).
5-19).

Next, a commercially available reagent of 47% hydrofluoric acid,
Using a 30% hydrogen peroxide solution and ion-exchanged water, mixing was performed so as to obtain the composition shown in Table 6, and 500 ml of each chemical polishing treatment solution was prepared.

Next, the prepared polishing sample was degreased with an alkali, immersed in each polishing solution maintained at the temperature shown in Table 6, and treated for 2 minutes. Subsequently, washing, draining, and drying were performed in the same manner as in the first example, the presence or absence of surface gloss and the polishing depth were measured, and the polishing rate was calculated. Table 6 shows the results.

[0074]

[Table 6]

Fifth Embodiment

Using the same material to be processed as in the first embodiment,
Similarly, carburizing and quenching were performed to obtain a polished sample.

Next, a processing solution having the same composition as the sample No. 2 of the first embodiment (a high-concentration processing solution) and a processing solution having the same composition as the sample No. 1 of the same embodiment (a low-concentration processing solution) were prepared. did.

Next, the polishing sample was immersed in the high-concentration processing solution for 3 minutes to perform a chemical polishing treatment.
Hold for about 20 seconds. Thereafter, the polishing sample was further dipped in the low-concentration processing solution for 10 seconds, pulled up, and held for about 20 seconds.

Next, washing, draining and drying were performed in the same manner as in the first embodiment. As a result, a product having more excellent surface gloss was obtained.

For comparison, after a chemical polishing treatment with a high-concentration processing solution was performed in the same manner as in the present embodiment, the polishing sample was pulled up and held for about 20 seconds, washed, drained, and treated without a low-concentration processing solution. Drying was performed. As a result, although gloss was obtained by the chemical polishing treatment, the retention time before the water washing treatment was long, so that the reaction proceeded more or less because the reaction proceeded further.

Continuation of the front page (72) Inventor Hideo Aihara 1st Toyota Town, Toyota City, Aichi Prefecture Examiner, Toyota Motor Corporation Investigator Takeshi Suzuki (56) References JP-A-59-173279 (JP, A) 6691 (JP, B2) International Publication No. 91/5079 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23F 3/06

Claims (3)

(57) [Claims] Claims: 1. A glossy chemical polishing treatment liquid for hardened steel members, comprising hydrofluoric acid having a concentration of 0.2 to 2 mol / l and a concentration of 0.4 to 4 mol.
/ 1 hydrogen peroxide, wherein the molar ratio of the hydrofluoric acid to the hydrogen peroxide is 1: 1.5-2.8. . 2. A step of hardening a steel member, a hydrofluoric acid having a concentration of 0.2 to 2 mol / l and a concentration of 0.4 to 4 mol.
/ L of hydrogen peroxide, and the hardened steel member is chemically polished in a bright chemical polishing solution having a molar ratio of the hydrofluoric acid to the hydrogen peroxide of 1: 1.5 to 2.8. A polishing chemical polishing treatment method for a hardened steel member. 3. A step of hardening a steel member; a hydrofluoric acid having a molar concentration of 0.8 to 1.5 mol / l;
The hardened steel member is chemically polished with a chemical polishing solution having a high concentration of 1.6 to 3.0 mol / l of hydrogen peroxide, wherein the molar ratio of the hydrofluoric acid to the hydrogen peroxide is 1: 1.6 to 2.4. A first chemical polishing treatment step; hydrofluoric acid having a molar concentration of 0.2 to 0.8 mol / l;
A hardened steel member composed of 0.4 to 1.6 mol / l of hydrogen peroxide, and having been subjected to the primary chemical polishing treatment with a chemical polishing treatment liquid having a low molar ratio of the hydrofluoric acid to the hydrogen peroxide of 1: 1.5 to 2.8. A chemical polishing process for chemically hardening the hardened steel member.