JPH11230880A - Method for adding mark for verifying state of crack development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the addition of a mark for verifying the state of crack development to a material which does not allow a beach mark. SOLUTION: A clad metal 5 in which a fatigue pre-crack 2 is formed on the surface of a clad part 4 buttered on a base metal 1 is treated by a process to impose loads repeatedly so that the fatigue pre-crack 2 may develop to form a crack 6 and a thermally treating process to heat the clad metal 5 on which a required number of repeated loads have been imposed at a predetermined temperature over a predetermined period of time. By this, it is possible to obtain the superior result that a mark for verifying the state of crack development can be added to a material which does not allow what is called a beach mark.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of providing a crack progress confirmation mark on a clad material.

[0002]

2. Description of the Related Art For example, when mechanically introducing fatigue cracks into a base material of the same material such as low alloy steel, generally, a fatigue prediction such as an EDM (Electric Discharge Machining) notch is formed on the surface of the base material. A crack is formed, a load is repeatedly applied to the base material by a three-point bending test machine or the like so that the pre-fatigue crack propagates, and a stress is applied to the pre-fatigue crack portion to form a crack.

[0003] As a typical method for confirming the progress of cracks imparted to the base material, there is a method of giving a beach mark to the base material. The procedure is as follows.

That is, as shown in FIG. 2, a pre-fatigue crack 2 is given to the surface of a base material 1 made of a low alloy steel, and a predetermined amount of heat is applied to the base material 1 per unit time so that the pre-fatigue crack 2 propagates and cracks. Prescribed load (maximum stress and minimum stress) by repeated load times
give.

Next, when a beach mark is provided, at least one of the number of repetitive loads per unit time or at least one of the loads is changed to a value different from the initial value, that is, the test conditions are changed, and Similarly, a predetermined load is applied at a predetermined number of times in the direction in which the pre-fatigue crack 2 of the base material 1 propagates.

Hereinafter, when a load is repeatedly applied in the same manner, a beach mark is substantially concentrically formed in the thickness direction of the base material 1 around the vicinity of the pre-fatigue crack 2 in a portion where the test condition of the base material 1 is changed. Mark 3 is given.

Since there is a correlation between the position at which the mark 3 is generated, the number of repetitions, and the applied load, the base material 1 is broken from the portion where the pre-fatigue crack 2 is applied, and the generation state of the mark 3 The progress of cracking in the material 1 can be confirmed.

On the other hand, as shown in FIG. 3, a clad material 5 in which a clad portion 4 is formed by buttering a stainless steel clad material or inconel, which is a nickel-based metal, on a base material 1 of low alloy steel is also used. A pre-fatigue crack 2 is formed on the surface, a repetitive load is applied to the clad material 5 under a certain load condition so that the crack propagates from the pre-fatigue crack 2, and a test condition is changed to repeatedly apply a load. The clad material 5 was observed for breakage.

[0009]

However, in the case of the clad material 5 shown in FIG. 3, the mark 3 is provided on the base material 1 but not on the clad portion 4, and therefore the mark 3 is not provided. There is a problem that the progress of cracking cannot be confirmed for the portion No. 4.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a mark for confirming the progress of cracking even in a portion where a beach mark does not enter, such as a clad portion. .

[0011]

According to the present invention, there is provided a method for providing a crack progress confirmation mark according to the present invention, comprising the steps of: And a heat treatment step of heating the clad material to which a required number of repetitive loads have been applied.

Therefore, according to the present invention, a mark for checking the progress of cracking can be provided even for a material to which a beach mark cannot be provided.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of an embodiment of the present invention, in which the same components as those shown in FIG. 3 are denoted by the same reference numerals.

In the embodiment of the present invention, the operating conditions such as the number of repetitive loads per unit time and the time for applying the repetitive load to the three-point bending tester or the like are set, and the cladding part 4 is set.
In the clad material 5 having the fatigue pre-crack 2 formed on the surface of
The repetitive load is applied so that the fatigue pre-crack 2 is promoted and the crack 6 is formed.

When the load is repeatedly applied for a predetermined time, the operation of applying the load is interrupted and the clad material 5 is removed.
Is heated at a temperature of, for example, 500 ° C. for 2 hours to perform a heat treatment. After the heat treatment, the pre-fatigue crack 2 is promoted in the clad material 5 under predetermined operating conditions by a three-point bending tester or the like, and a crack 6 is further formed. Apply a load repeatedly.

When a predetermined number of repetitive loads are applied, the operation of applying the repetitive load is interrupted, and the clad material 5 is heated at a temperature of, for example, 300 ° C. for 2 hours to perform a heat treatment. A load is repeatedly applied to the clad material 5.

After performing the repetitive load applying step and the heat treatment step a required number of times, the clad part 4 was fractured from the portion of the pre-fatigue crack 2, and the clad part 4 was cracked as shown in FIG. In correspondence with No. 6, a mark 7 called a heat paint mark was provided. This mark 7 appears due to the difference in the degree of burning of the metal between the part where the crack 6 is included and the part where the crack 6 is not included.

Therefore, in the clad portion 4, the progress of the crack 6 could be confirmed by observing the mark 7 provided by the heat treatment.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the spirit of the present invention.

[0021]

According to the method for imparting a crack progress confirmation mark of the present invention, there is an excellent effect that a mark for confirming the progress of cracking can be given to a material to which a so-called beach mark cannot be given. obtain.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a method for imparting a crack progress confirmation mark according to the present invention.

FIG. 2 is a cross-sectional view for explaining a conventional method for assigning a crack progress confirmation mark.

FIG. 3 is a cross-sectional view for explaining that a beach mark does not enter a clad portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Pre-fatigue crack 4 Cladding part (material without beach mark) 5 Cladding material 6 Crack

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasuho Sato 1 Shinnakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Ishikawajima-Harima Heavy Industries Co., Ltd. (72) Inventor Hiroshi Sakamoto Shinnaka, Isogo-ku, Yokohama-shi, Kanagawa No. 1 Haramachi Ishi Kawashima-Harima Heavy Industries Co., Ltd.

Claims (1)

[Claims] A step of repeatedly applying a load to a clad material having a pre-fatigue crack formed on a surface of a material which does not include a beach mark buttered on a base material so that the pre-fatigue crack propagates and a crack is formed; A method for providing a crack progress confirmation mark, wherein the method is performed by a heat treatment step of heating a clad material to which a repetitive load is applied.