JPH04350116A - Method for hardening metallic material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a method for hardening metal materials, and in particular to hardenability of metal materials such as steel.
The present invention also relates to a method that makes it possible to selectively control the hardening depth after quenching.

0002

BACKGROUND OF THE INVENTION When hardening metal materials, the strength of the hardened product is generally determined by the surface hardness and hardening depth, and it is important to optimally control these factors. In particular, the hardening depth is important in ensuring fatigue strength, wear life, etc. In general, the hardening depth is determined by the hardenability (DI value) of the metal material, which is determined by the composition and amount of the metal material, the quenching method, and the cooling ability of the quencher.

[0003] In the normal quenching method, the entire processed product is uniformly hardened to form a hardened layer, so when it is desired to form a hardened layer on a required part of the processed product, it is necessary to locally harden the processed product. The quenching process required special measures, such as high-frequency heating or locally preventing contact with the cooling medium during the quenching process.

[0004] Generally, in order to deepen the hardened layer,
For example, for steel materials, Mn, Cr, Si, Ni, Mo
, B, etc. are widely added to steel materials as alloying components. In particular, in recent years, B-added steel, which is a steel material with boron added, has been used in many fields because it is relatively inexpensive and allows the hardening layer to be deep.

[0005]

[Problems to be Solved by the Invention] In the conventional method as described above, although it is possible to create hardened parts and non-hardened parts in the processed product, it is difficult to harden the hardened part in the hardened part. The problem was that it was not possible to change the In addition, even when adding elements in advance to deepen the hardening depth of metal materials, even if the hardening depth of the entire treated product can be uniformly deepened, the hardening depth itself may be partially selected. The technology to change this has not yet been established. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for hardening a metal material that makes it possible to partially change the depth of hardening that occurs during hardening.

[0006]

[Means for solving the problem] In order to solve the above-mentioned problem, a hardening accelerator that deepens the hardening depth is penetrated only into the part of the metal material where the hardening depth is to be increased, and then the hardening treatment is performed. conduct. That is, the gist of the method for hardening a metal material according to the present invention is to partially infiltrate a metal material with a quenching accelerator and then perform a treatment to vary the hardening depth.

Powder or paste containing boron (B) is used as the quenching accelerator.

Methods for partially penetrating a metal material with a quenching accelerator include (1) a method of holding a treated product whose surface has been partially masked in an atmosphere of a quenching accelerator;
) A method of attaching a paste contained in a quenching accelerator to a part of the surface of the treated product, (3) Holding the treated product with at least a part of the surface masked in a fluidized bed using the quenching accelerator as fluidized particles. methods, etc. are applicable.

[0009]

[Operation] The hardening depth of the part of the metal material penetrated by the quenching accelerator is greater than that of the part not penetrated by the quenching accelerator. This causes local changes in the hardenability of the metal material, that is, the hardening depth. At the same time, by controlling the permeability of this quenching accelerator into the metal material, it becomes possible to select the depth of hardening of the metal material by quenching to a desired value.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, some specific embodiments of the present invention will be described with reference to the drawings. In Examples 1 to 3, a 20t pipe of S53C was used as the treated product.

(Example 1) As shown in FIG. 1(a), first, a masking 2 was applied to a part of the product 1 to be treated. This masking method includes attaching a ceramic heat-resistant sheet that functions as a so-called carburization prevention material, and
There are methods such as applying plating such as r.

Next, the treated product 1 is subjected to a boron infiltration treatment in a furnace 3, as shown in FIG. 1(b). Inside the furnace 3, boron trichloride, boron tribromide, methyl triboride,
A boron-containing gas 4 made of ethyl triboride or the like is introduced and heated to an austenite temperature range of 800° C. or more.

[0013] While the product is kept in such a boron-containing heated atmosphere for 30 minutes or more, boron diffuses and permeates from the surface of the product to the inside. At this time, the boron-containing gas will not be adsorbed on the surface of the treated product in the areas where masking 2 has been applied, and even if it is adsorbed, its penetration into the steel in that area will be inhibited by masking 2 and will be extremely small. , or the rate of penetration is significantly reduced. After heating and simultaneous boron penetration treatment, the treated product 1 from which the masking 2 has been removed is immersed in a quenching medium 5 such as oil to be quenched, as shown in FIG. 1(C). For example, if the material has already been heated to the austenite temperature range, it is possible to directly quench it in this way.

In addition, when performing boron penetration treatment and carburizing treatment on the same treated product at the same time, a mixed gas of a boron-containing gas and a carburizing gas is introduced into the furnace 3, and the treated product is added to the mixed gas. hold. When this method is used, the part where the surface hardness increases due to carburization overlaps with the part where the hardening depth increases, resulting in a larger change in hardenability between the part where masking 2 is applied and the part where hardening treatment is applied. It will be done.

(Example 2) A boron-containing paste 6 made by mixing ferroboron with water glass was applied and adhered to a part of the treated product 1 as shown in FIG. This is maintained at a high temperature of 800° C. or higher to diffuse and infiltrate the interior of the treated product from the portion where the boron-containing paste 6 is applied. The hardening treatment is performed in the same manner as in Example 1. Processed product 1
The boron-containing paste 6 adhering to the wafer is peeled off and removed during this quenching process. Finally, the treated surface can be polished if necessary.

(Example 3) Similar to Example 1, treated product 1
Masking 2 was applied to a part of the area using a heat-resistant sheet or the like. This treated product 1 is set in a fluidized bed furnace 7 shown in FIG. By using boron-containing powder 9 in at least a part of the particles,
Fluidized bed heating and boron infiltration treatment of treated product 1 are performed in parallel. At the same time, boron is infiltrated into the treated product 1 in a fluidized bed containing boron-containing powder 9. As a specific example of the fluidized particles or the boron-containing powder 9 contained in the fluidized particles, a powder obtained by adding a catalyst to boron, such as boron fluoride or boron carbide, is used.

Furthermore, as the fluidizing gas 10 introduced into the fluidized bed furnace 7 to fluidize this boron-containing powder, a non-oxidizing gas such as N2 gas or Ar gas, or a reducing gas such as H2 gas may be used. is suitable. The quenching treatment may be performed in the same manner as in Example 1, but instead of immersion in oil, it may be performed in a fluidized bed in which the fluidized particles are replaced with alumina.

Looking at the curing patterns of the various examples described above, it was found that the method of Example 1 cured 900
Regarding the treated product 1 in FIG. 4 obtained by performing boron penetration treatment at ℃ for 4 hours, the hardness and hardening depth of the hardened layer A on the side impregnated with boron and the hardened layer B on the side subjected to masking 2. When measured, a pattern as shown in FIG. 5 was obtained. As you can see, the hardness is 513H
The effective hardening depth of v or more is 3.5 mm on the A layer side,
The hardening depth was 3.0 mm on the B layer side, and it was confirmed that the hardening depth of the part where the boron infiltration treatment was performed was large. Example 2
Similar results were obtained for the treated products obtained in Steps 3 and 3.

[0019] The above description has been made for the case where the metal material to be hardened is steel, but even if the metal material is other than steel, the hardening process can be performed by selecting a hardening accelerator that is compatible with the metal material. Needless to say.

[0020]

[Effects of the Invention] Conventional hardening techniques either obtain a uniform hardening depth over the entire steel material, or perform hardening partially to form a hardened layer only in the hardened portion. There were only two ways. In contrast, in the method according to the present invention, by performing a treatment to partially change the hardenability before hardening, the hardening depth of the hardened layer is reduced even though the entire steel material is hardened. It became possible to cause partial changes in the

As a result, for a single steel material, the hardening depth can be increased in areas where fatigue strength and wear resistance are particularly required, and the hardening depth can be decreased in the remaining areas to ensure toughness. It is now possible to control the hardening depth of steel materials according to the As described above, the present invention has developed a new hardening technology for steel materials, and this technology provides steel materials with extremely high utility value that have novel hardening characteristics not previously available.

[Brief explanation of the drawing]

FIG. 1 (a), (b), and (c) are schematic diagrams showing the steps of Example 1.

FIG. 2 is a state diagram of masking in Example 2.

FIG. 3 is a schematic diagram showing the state of fluidized bed heating in Example 3.

FIG. 4 is a cross-sectional view of a treated product obtained in Example 1.

FIG. 5 is a graph showing the curing pattern of the treated product shown in FIG. 4;

[Explanation of symbols]

1. Processed products 2 Masking 3 Furnace 4 Boron-containing gas 5 Quenching medium 6 Boron-containing paste 7 Fluidized bed furnace 8 Dispersion plate 9 Boron-containing powder

Claims (5)

[Claims] 1. A method for hardening a metal material, which comprises performing a quenching treatment after partially infiltrating a treated product with a quenching accelerator. 2. The method for curing a metal material according to claim 1, wherein the quenching accelerator contains boron. [Claim 3] A claim characterized in that the quenching accelerator partially penetrates into the treated article by masking a part of the surface and holding the treated article in an atmosphere of the quenching accelerator. Item 2. The method for curing a metal material according to item 1 or 2. 4. The method of claim 1 or 2, wherein a paste containing the quenching accelerator is attached to a part of the surface of the quenching accelerator, so that the quenching accelerator is partially infiltrated into the treated article. The method for curing metal materials described in . 5. The quenching accelerator is partially infiltrated into the treated article by holding the treated article with at least a portion of its surface masked in a fluidized bed using the quenching accelerator as fluidized particles. The method for curing a metal material according to claim 1 or 2, characterized in that: