JP3050964B2 - Partial nitriding and quenching of parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for partially nitriding or partially carburizing and quenching parts.

[0002]

2. Description of the Related Art Quenching is not required in a partial nitriding quenching method or a partial carburizing quenching method in which only parts near the tip of a drilling tapping screw are nitrided or carburized and quenched. A method of applying a nitriding agent or a carburizing agent to the part and quenching it, or nitriding or carburizing and quenching the entire part, and then forming a nitrided quenching layer or A method of removing a carburized quenched layer by dissolving it with a chemical is known.

The above-mentioned drilling tapping screw can make a pilot hole, cut a screw, and fix it by simply screwing it in, so that the working time can be made extremely short. Is expanding rapidly. In the field where corrosion resistance is required, a drilling tapping screw using austenitic stainless steel is known. When the head, screw, and drill are integrally formed of austenitic stainless steel, the corrosion resistance is excellent, but the hardness of the austenitic stainless steel is low, so the drilling performance of the drill is poor, and Cannot be used. Therefore, in the case of a drilling tapping screw, it is conceivable to increase the hardness of only the drilled portion and the threaded portion in the vicinity of the drilled portion by partially nitriding or partially carburizing and quenching. According to the partial nitriding quenching or the partial carburizing quenching, since the surface of the head and the part involved in the tightening remain the austenitic stainless steel, the feature of high corrosion resistance can be secured.

As described above, as a method of performing nitriding quenching or carburizing quenching on only a part of a part, as described above, a nitriding agent or a carburizing agent is applied to a portion not requiring quenching. In the quenching method, there is a problem that a nitriding agent and a carburizing agent must be evenly applied to portions where quenching is unnecessary. Also, after applying a nitriding agent and a carburizing agent, baking and drying at a predetermined temperature are required,
Thereafter, nitriding quenching or carburizing quenching must be performed, and furthermore, a nitriding agent and a carburizing agent must be removed, which requires a complicated processing step and requires these processing equipment.

The method of nitriding and carburizing and quenching the entire part and then dissolving a quenched layer formed in an unnecessary part by a chemical involves dissolution of the quenched layer. In addition, there is a problem that a dimensional change of a part occurs, and the function of the part deteriorates.

In the case of a drilling tapping screw, after the entire surface is nitrided, the nitrided layer of the head and the screw portion near the head is removed, and the shape of the head is changed by melting the nitrided layer. In particular, in the case of a cross-recessed screw or the like, there is a problem that the tool may run idle or the screw may fall off the tool during the tightening operation. At the screw portion near the head, there is a problem that the outer diameter of the screw at that portion is reduced due to the removal of the nitride layer, and the female screw is broken at the time of tightening.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to remove an unnecessary quenched layer after quenching without using a nitriding agent or a carburizing agent. It is another object of the present invention to provide a method of partially nitriding and partially carburizing and quenching parts that can be partially nitrided and partially carburized and quenched by a simple method.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for partially nitriding and partially carburizing and quenching a part, in which a part of the part is immersed in a treatment liquid and the other part is air or a chemically stable gas. Characterized by being covered by

[0009]

The quenching unnecessary portion is covered with air or a chemically stable gas to prevent nitriding or carburizing due to the gas generated from the surface of the processing solution, and nitriding quenching or immersing only in a desired portion. Charcoal quenching can be performed.

[0010]

FIG. 1 is a schematic structural view of an embodiment in which the present invention is applied to partial nitriding and quenching of a drilling tapping screw.
In the figure, 1 is an austenitic stainless steel drilling tapping screw, 2 is a treatment liquid, 3 is a holding plate, 4 is a container,
5 is a gas inflow pipe, 6 is a regulator for adjusting inflow pressure, 7
Is an atmosphere discharge pipe, and 8 is a regulator for adjusting the outflow pressure. The holding plate 3 is provided with a hole substantially equal to the outer diameter of the screw portion of the drilling tapping screw 1, and the drilling tapping screw 1 is suspended in this hole, and is fixed to the container in an airtight manner by screwing or the like. . The lower part of the drilling tapping screw 1 suspended from the holding plate 3 attached to the lower part of the container 4 is immersed in the treatment liquid 2, and the immersed part is subjected to nitriding treatment. Pressurized air is introduced into the container 4 from the gas inflow pipe 5 via a regulator 6 for adjusting inflow pressure. Thereby, the pressure inside the container 4 is higher than the pressure outside the container.
For example, it is kept at a predetermined air pressure 1 kg / cm ² higher.
The pressure may be adjusted such that the air pressure in the container 4 is released from the atmosphere discharge pipe 7 through the outflow pressure adjusting regulator 8. Due to the high pressure in the container 4, the air introduced into the container 4 during the nitriding process flows out of the gap between the hole of the holding plate 3 and the drilling tapping screw 1, and the processing of the drilling tapping screw 1 is performed. Since the portion that is not immersed in the liquid 2 is covered, the portion is not nitrided by a gas or the like generated from the liquid surface of the processing liquid 2, and a nitriding film is formed only on the surface of the immersion portion.

In order to make it easier for air to flow out from between the holding plate 3 and the lower surface of the head of the drilling tapping screw 1 and to make the outflow resistance uniform, the head of the drilling tapping screw 1 in the holding plate 3 is Fine projections or grooves may be provided on the upper surface of the contacting portion.

The gas introduced from the gas inlet pipe 5 is
It is sufficient if the gas is chemically stable for nitriding.
An inert gas such as He, Ne, Ar, Kr, Xe, or Rn, or an appropriate gas such as CO ₂ or N ₂ can be used.

As shown in FIG. 2A, a hole for suspending a drilling tapping screw in the holding plate 3 is, for example,
A hole into which a drilling tapping screw can be individually inserted may be provided like the circular hole 3a, or FIG.
As shown in FIG. 7, a slit-shaped opening 3b may be provided. In FIG. 1, two rows of holes are arranged.
A row or three or more rows may be used, and a slit-like holding hole may be used.

FIG. 3A shows another embodiment of the container.
In this embodiment, the bottom plate has a double structure of 4a and 4b, and the space A between the lid 4c and the bottom plate 4a is sealed.
And pressurized air is introduced from a not-shown introduction pipe into a space B between the first and fourth parts. The air flowing into the space A through the space between the space B and the head of the drilling tapping screw 1 increases the pressure in the space A, and after the pressure is balanced, the space B moves from the space B to the space A. There is no inflow. Therefore, the supplied pressure air blows an air flow to the drilling tapping screw 1 using the opening of the space B as a nozzle,
The surroundings of the drilling tapping screw 1 can be covered with an airflow by flowing downward around the surroundings.

As shown in FIG. 3B, holes 4 are formed in the bottom plate 4a.
d may be opened to facilitate pressure equilibrium. When the hole 4d is provided, pressurized air may be introduced into the space A.

FIG. 4 is a side view of an example of a drilling tapping screw subjected to a nitriding treatment, and FIG. 5 is a sectional view. In the figure, 1
1 is a head, 12 is a screw portion, 13 is a drill portion, A portion is a portion where a nitride film is not formed, and B portion is a portion where a nitride film is formed. Since the drill portion 13 has been subjected to the nitriding treatment, the surface hardness is high and the drilling performance is good. Since several ridges at the tip of the screw portion 12 connected to the drill portion 13 are also subjected to nitriding treatment, the hardness of the surface is similarly high. Therefore, tapping can be easily performed on the hole drilled by the drill portion 13. The hardness of this surface is required to be 400 or more in Vickers hardness and 40 μ or more in depth. If the hardness and depth do not reach the above-mentioned values, the performance of the austenitic stainless steel material decreases when drilling with a drill part and tapping with a screw part, because the material has low hardness. In some cases, drilling or tapping becomes impossible. In addition, since the head portion 11 and the screw portion in the vicinity of the head portion have not been subjected to nitriding treatment, they have the properties of an austenitic stainless steel material as they are, and have good corrosion resistance. The portion B where the nitride film is formed
Although a slight dimensional expansion is observed due to nitriding, this is not a problematic degree, and even in the complete thread portion, the diameter belonging to the portion A and the diameter belonging to the portion B are substantially equal. The drilling tapping screw can be stably fastened without any problems at the time or breakage of the internal thread at the time of fastening.

In the above-described embodiment, a drilling tapping screw has been described as a component. However, even if a component has a different shape, partial nitriding quenching or partial carburizing quenching can be immersed in a processing solution. It is clear that the present invention can be applied as long as the portion can be exposed outside the processing solution. The separation of the non-processing portion by the gas can be appropriately designed using a suitable holding structure, a nozzle, or the like.

[0018]

As is apparent from the above description, according to the present invention, the part of the component which is not immersed in the processing liquid can be covered with the gas, so that the desired part can be obtained without using a nitriding agent or a carburizing agent. There is an effect that partial nitriding quenching or partial carburizing quenching can be performed only on the portion.

[Brief description of the drawings]

FIG. 1 is a principle view of an embodiment in which the present invention is applied to partial nitriding quenching of a drilling tapping screw.

FIG. 2 is an explanatory diagram of a holding plate in FIG.

FIG. 3 is a sectional view of another embodiment of the container.

FIG. 4 is a side view of a drilling tapping screw manufactured according to the present invention.

FIG. 5 is a longitudinal sectional view of the drilling tapping screw of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drilling tapping screw 2 Processing liquid 3 Holding plate 4 Container 4a Bottom plate 5 Gas inflow pipe 6 Inflow pressure adjustment regulator 7 Atmospheric emission pipe 8 Outflow pressure adjustment regulator

Claims (1)

(57) [Claims] 1. A method for partially nitriding and partially carburizing and quenching a part, wherein a part of the part is immersed in a processing solution, and the other part is covered with air or a chemically stable gas. Partial nitriding and quenching methods.