JPH05345975A - Surface treating method for preventing hydrogen embrittlement - Google Patents

Abstract

PURPOSE:To prevent hydrogen embrittlement by vapor-depositing a chromium layer having a specified thickness on the surface of high strength steel for structural use and furthermore subjecting it to treatment for improving adhesion between both. CONSTITUTION:The surface of high strength steel for structural use having 100 to 150MPa tensile strength is vapor-deposited with a chromium layer having <=0.050mum film thickness by ion magnetron sputtering. As for the ion sputtering vapor deposition conditions, e.g. heating temp. is held at <=400 deg.C in vacuum of >=10<-2>Torr. Next, for preventing peeling caused by thermal stress generated at this time, argon ions of 10<16> to 10<17> pieces/cm<2> are implanted therein, and the boundary between the chromium layer and steel is subjected to ion mixing treatment, by which they are closely contacted at each other. In this way, the deterioration in the fatigue service life caused by the hydrogen embrittlement of the high strength steel by hydrogen intruding from the external environment can conveniently and easily be suppressed.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen embrittlement prevention surface treatment method. More specifically, the present invention relates to a surface treatment method for preventing hydrogen embrittlement, which can prevent the fatigue life of high-strength steel from decreasing due to hydrogen invading from the external environment.

2. Description of the Related Art Conventionally, in order to reduce the weight of structures and ensure safety, high-strength steels having excellent fatigue properties have been demanded, and have already been developed. Some strong steels have also been developed.
However, the higher the strength of the steel, the more the steel is used in a wet environment such as water vapor or an aqueous solution, which causes fatigue fracture at an early stage, impairing the good properties inherent to the steel. Structural high-strength steels generally have the disadvantage that when they come into contact with such an external environment, they undergo a corrosive reaction and are easily embrittled by the resulting hydrogen. Therefore, conventionally, the composition, structure, etc. of steel are controlled to reduce the susceptibility to hydrogen embrittlement. In addition to these, various measures for improving the corrosion resistance of high-strength steel have been proposed. For example, as one of them, a method of coating an organic or inorganic paint on the steel surface is known. However, in this case, since maintenance and inspection are required, there is a drawback that labor and cost become enormous. There is also known a method of applying electrical cathodic polarization to high-strength steel to prevent corrosion, but in this case, there is a risk of over-corrosion in a structure having a complicated shape. However, there is a problem of early fracture due to hydrogen embrittlement. Furthermore, although an electroplating method has been proposed as a surface treatment for imparting corrosion resistance, in this case, there is a problem that hydrogen absorption into the material occurs due to the plating treatment and hydrogen embrittlement is easily induced. .. As described above, even if corrosion resistance is imparted to high-strength steel, there is a problem that the fatigue strength is significantly reduced due to hydrogen invading during the surface treatment process or hydrogen invading from the external environment. The actual situation is that the anticorrosion method still has issues to be improved. The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a new hydrogen embrittlement prevention surface treatment method that can solve the drawbacks of the conventional method for improving the corrosion resistance of high-strength steel and prevent the deterioration of the fatigue life of high-strength steel due to hydrogen invading from the external environment. Has a purpose.

In order to solve the above problems, the present invention provides a chromium high-strength steel surface having a tensile strength of 100 to 150 MPa with a chromium layer having a thickness of 0.05 μm or less by N ion magnetron sputtering. Evaporated, then 10
^In the present invention, there is provided a hydrogen embrittlement prevention surface treatment method, characterized in that ¹⁶ to 10 ¹⁷ ions / cm ² of argon ions are injected to ion-mix the interface between a chromium layer and steel to bring the chromium layer into close contact. The tensile strength of the high-strength steel for the target structure is 100 to 150 MPa, which means that when the tensile strength is less than 100 MPa, the hydrogen embrittlement susceptibility of the steel itself is small, and , For steels greater than 150 MPa,
This is because the internal hydrogen that has entered during the manufacturing process is likely to cause embrittlement and has a small surface treatment effect. Also, chromium is used as the vapor deposition material. This is because the chromium layer reduces the amount of hydrogen that enters the steel material in a corrosive environment. As this chromium source, for example, a pure chromium plate of about 3N can be exemplified. Of course, it may be something other than this. In the present invention, the magnetron sputtering method is used as a method for depositing the chromium layer on the steel surface.
The magnetron sputtering method using argon ions or the like is a physical surface treatment method and a dry surface treatment method. Therefore, hydrogen can be prevented from entering the steel during the surface treatment. As the vapor deposition conditions,
For example, in a vacuum of 10 ^-2 Torr or more, heating temperature is 400 ℃
You can keep: The thickness of the chromium layer at this time is 0.050 μm or less. When the film thickness is larger than 0.050 μm, the thermal stress generated during the surface treatment tends to cause peeling after the vapor deposition, and it is difficult to improve the adhesion by the ion mixing treatment after the vapor deposition. Furthermore, in the present invention, after the chromium layer is deposited by the magnetron sputtering method, the interface between the chromium layer and the steel is ion-mixed with 10 ¹⁶ to 10 ¹⁷ ions / cm ² of argon ions. Although the chromium coating can be prepared by the magnetron sputtering method alone, the combined use of the ion mixing method is indispensable for improving the fatigue life of the steel material and making the coating stable under stress. This ion mixing treatment improves the adhesion of the chromium layer, improves the corrosion resistance of structural high-strength steel, suppresses the intrusion of hydrogen from the external environment, and suppresses the reduction in fatigue life due to hydrogen embrittlement. It becomes possible to do. The ion mixing process can be performed at room temperature, for example. in this way,
In the present invention, the treatment temperature during the vapor deposition of the chromium layer and the ion mixing treatment can be sufficiently lowered, so that the surface treatment can be stably performed without impairing the characteristics of the steel material.

EXAMPLES Examples are shown below to prevent hydrogen embrittlement of the present invention.
The surface treatment method will be described in more detail. SNCM4
39 steel was oil-quenched at 840 ℃, then tempered at 480 ℃,
The tensile strength was adjusted to 120 MPa. Mechanically polish this steel and
After degreasing with Seton, 10^-2Heating temperature under Torr vacuum
The temperature is maintained at 150 ° C, and a chromium substrate is used to
Magnetron sputtering was performed. This steel
Deposited 0.808 μm and 0.037 μm chrome layers on the material
Then 10 ¹⁶-10¹⁷Pieces / cm²Of argon ions
Irradiated. For comparison, the magnetron spa under the same conditions
Ion deposit a chrome layer of the same thickness by
A steel material not subjected to the mixing treatment was also produced. Above samples
About the presence or absence of peeling of the deposited chromium layer under fatigue loading.
As a result of examination, it was found that a 0.808 μm thick chromium layer was vapor-deposited.
As for the material, as-is and as-sputtering
Even if ion mixing is applied after the ring, the chromium layer
Peeling occurred. On the other hand, a chrome layer with a thickness of 0.037 μm was vaporized.
About the sample that has been ion-mixed after it is put on
No peeling of the chromium layer occurred. Next, this film thickness of 0.
Ion mixing after depositing 037 μm chromium layer
A cathode potential of -1.2 V was applied to the treated sample and water was applied.
Fatigue in 3.5% NaCl solution while charging the element
The test was conducted. Also, for comparison, a chrome layer was deposited.
The same fatigue test was performed on the untreated material. That
Table 1 shows the results. Clear from Table 1
Thus, the fatigue life of surface-treated steel is untreated.
It has improved to a little less than 5 times the material. Improving fatigue life
Was confirmed. Of course, this invention is
It is not limited. Such as the type of steel and heat treatment
It goes without saying that various details are possible.
Nor.

[Table 1]

As described in detail above, according to the present invention, embrittlement due to hydrogen invading from the external environment is suppressed,
The fatigue life of high strength steel can be easily and easily improved.

Claims (2)

[Claims] 1. A film thickness of 0.1.000 by ion magnetron sputtering on the surface of a structural high strength steel having a tensile strength of 100 to 150 MPa.
Deposit a chromium layer of 050 μm or less, then 10 ¹⁶ -10
^A surface treatment method for preventing hydrogen embrittlement, which comprises injecting ¹⁷ ions / cm ² of argon ions to ion-mix the interface between a chromium layer and steel to bring the chromium layer into close contact. 2. The surface treatment method for preventing hydrogen embrittlement according to claim 1, wherein the chromium layer is deposited by magnetron sputtering while maintaining the heating temperature at 400 ° C. or less in a vacuum of 10 ⁻² Torr or more.