JP3908120B2 - Manufacturing method of high strength stainless steel for elastic substrate of load sensor - Google Patents

Description

【００２２】
【発明の効果】
以上の説明から明らかなように、本発明によれば荷重センサーの弾性基板において高耐力が得られ、新規設備を必要とせず、効率的に荷重応答性に優れた荷重センサーを提供することができる。そして、家電、自動車、重機、建築物などの必要部位において、検知精度が著しく優れた測定が可能となる。
【図面の簡単な説明】
【図１】ステンレス鋼におけるσ相生成量と耐力の関係を示す図である。
【図２】ステンレス鋼における熱処理条件とσ相生成量の関係を示す図である[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-strength stainless steel suitable for an elastic substrate of a load sensor having excellent load response and a method for manufacturing the same.
[0002]
[Prior art]
In general, a load sensor has a structure in which an operation part for transmitting an external force transmits a load to an expansion / contraction part composed of a ceramic strain resistance element and a metal elastic substrate. The load is transmitted from the operation site to the elastic substrate, and the resistance value of the strain resistance element changes according to the deformation of the elastic substrate to detect the load in the two-dimensional direction.
[0003]
Conventionally, a metal material is used for the elastic substrate in the load sensor, but when the elastic substrate has low proof stress, when the excessive load is applied instantaneously, the elastic substrate is plastically deformed, and the load is accurately measured. There was a problem that could not be measured. Japanese Patent Application Laid-Open No. 8-145819 describes a load sensor that has high reliability even when a material having low yield strength is used. The load sensor is high and reliable.
[0004]
As a method for increasing the yield strength of an elastic substrate, there is a method of performing cold working at the time of steel production, but there is a drawback that the number of production steps increases. In addition, even if the yield strength is increased by work hardening, heat treatment is generally performed for bonding to a strain resistance element made of ceramic or resin, and strain is removed and softened at that time. The proof stress will be reduced.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a high-strength stainless steel suitable for an elastic substrate of a load sensor and the like by solving the problems of the known techniques.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors conducted detailed studies on the characteristics required for the elastic substrate of the load sensor from the viewpoints of metallography and material control. It is possible to increase the yield strength by precipitating
(1) In mass%, C: 0.01-0.10%, Cr: 15-30%, Ni: 5-25%, Mo: 0.5-8%, N: 0.10-0. 20%, the stainless steel balance being Fe and unavoidable impurities, by heat treatment of more than 10min at 600 to 900 ° C., in the presence of σ-phase 1-40%, the heat treatment is at load sensor manufacturing, other A method for producing high-strength stainless steel for an elastic substrate of a load sensor, which is performed in a heat treatment for bonding to a member .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The reason for limitation of the present invention will be described below.
[0008]
In order to improve the load responsiveness of the load sensor, it is necessary to improve the responsiveness of the resistance value of the strain resistance element. For that purpose, it is better that the proof stress in the mechanical properties of the elastic substrate is high. If the proof stress is low, an accurate load cannot be measured due to plastic deformation, and the instantaneous response will deteriorate. Therefore, it was found effective to increase the yield strength by generating an intermetallic compound in the elastic substrate, and attention was paid to the σ phase as an intermetallic compound for increasing the yield strength.
[0009]
FIG. 1 shows the relationship between the amount of σ phase produced and the yield strength when heat treatment is applied to austenitic stainless steel under various conditions to precipitate the σ phase. The amount of sigma phase produced was measured by observing the cross-sectional structure, and the sigma phase production area ratio was measured 10 times at 500 times with an image analyzer, and the average value was obtained. The proof stress is a 0.2% proof stress value when a JIS No. 13 B test piece is collected and a tensile test in a direction parallel to the rolling direction is performed.
[0010]
The yield strength is remarkably improved by the increase of the σ phase, and the yield value becomes 600 N / mm ² or more by the generation of 1% or more. In general, the load responsiveness of the load sensor is governed by the yield strength of the elastic substrate, and when it is 600 N / mm ² or more, sufficient load responsiveness is obtained, so the lower limit of the σ phase is set to 1%. On the other hand, the σ phase causes embrittlement of the steel material, but since the elastic substrate in the load sensor is protected from the outside by the housing structure, a certain increase in the σ phase is allowed. However, if the sigma phase exceeds 40%, it becomes extremely brittle and may not be able to withstand the impact during sensor assembly, and it is necessary to strengthen the load sensor housing structure, so the upper limit was made 40%.
[0011]
The formation of the σ phase is mainly composed of Fe, Cr, and Mo, and stainless steel containing these elements is preferably used. Hereinafter, a preferable component composition will be described.
[0012]
C is an element that suppresses the corrosion resistance and also suppresses the formation of the σ phase, so a lower value is desirable. However, excessive reduction leads to a decrease in base yield strength and an increase in refining cost, so 0.01 to 0.10% It was. Furthermore, considering the manufacturing cost and manufacturability, the C content is preferably 0.02 to 0.05%.
[0013]
Since Cr is an element that promotes the generation of σ phase and is an element that improves corrosion resistance and oxidation resistance, a larger amount is desirable, but excessive addition brings about a high manufacturing cost, so the content was made 15 to 30%. Furthermore, considering the suppression of scale formation during the heat treatment during sensor production, corrosion resistance, and the production cost, the Cr content is preferably 22 to 27%.
[0014]
Ni is added to ensure corrosion resistance and oxidation resistance, but excessive addition leads to an increase in cost, so it was made 5 to 25%. Furthermore, considering the suppression of scale formation and corrosion resistance during heat treatment during sensor manufacture, and the steel manufacturability, the Ni content is preferably 5 to 20%.
[0015]
Mo is an element that promotes the generation of the σ phase and is an element that improves the corrosion resistance. Therefore, a larger amount is desirable, but excessive addition causes a decrease in productivity due to an increase in cost and brittleness. 5-8%. Furthermore, if considering oxidation resistance and manufacturing cost, 1.5 to 3.5% is desirable.
[0016]
N is an element that improves the corrosion resistance and strength, but who often desirable, since excessive addition result in reduced cost increases and productivity, yet excessive addition suppresses σ phase formation other, manufacturing cost In consideration of productivity, the N amount is preferably 0.10 to 0.20%.
[0017]
FIG. 2 shows the relationship between the heat treatment temperature of stainless steel and the amount of σ phase produced. From this, when the temperature exceeds 900 ° C., the σ phase is dissolved, and the necessary amount cannot be obtained, so the upper limit is set to 900 ° C. Further, when the temperature is lower than 600 ° C., Cr nitride and carbide are more stably precipitated than the σ phase, and the amount of σ phase generated decreases, so the lower limit is set to 600 ° C. This σ-phase generation heat treatment may be performed after being processed as an elastic substrate. For example, if the heat treatment is performed for bonding with other members of the load sensor, the yield strength can be increased efficiently. The atmosphere for this heat treatment may be any atmosphere, regardless of heating conditions and cooling conditions. Further, the heat treatment time is the total time, and the σ phase can be generated even by repeated heat treatment, so the total holding time at 600 to 900 ° C. may be 10 min or more.
[0018]
【Example】
Stainless steel having the composition shown in Table 1 is melted and cast, then hot-rolled, hot-rolled sheet continuous annealing / pickling is performed, cold-rolled to 2.0 mm thickness, continuous annealing-pickling, temper rolling. To give a product. This product was heat-treated under the conditions shown in Table 1.
[0019]
With respect to the sample obtained as described above, the amount of σ phase produced and the yield strength were measured. The measuring method is the same as the method described above.
[0020]
As apparent from Table 1, there σ phase 1 to 40% component composition in addition to the σ phase is in the range of claim 1, and heat treatment conditions is in the range of claim 2 No. It can be seen that 3 to 12 have higher proof stress than the comparative example .
[0021]
[Table 1]

[0022]
【The invention's effect】
As is clear from the above description, according to the present invention, a high yield strength can be obtained in the elastic substrate of the load sensor, a new sensor can be efficiently provided without a new facility, and an excellent load response can be provided. . And it becomes possible to perform measurement with remarkably excellent detection accuracy in necessary parts such as home appliances, automobiles, heavy machinery, and buildings.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between the amount of σ phase produced and the yield strength in stainless steel.
FIG. 2 is a graph showing the relationship between heat treatment conditions and sigma phase generation in stainless steel.

Claims (1)

In mass%, C: 0.01 to 0.10%, Cr: 15 to 30%, Ni: 5 to 25%, Mo: 0.5 to 8%, N: 0.10 to 0.20%, Stainless steel with the balance consisting of Fe and unavoidable impurities is subjected to heat treatment at 600 to 900 ° C. for 10 min or longer to cause 1 to 40% of σ phase, and the heat treatment is combined with other members at the time of load sensor production. A method for producing a high-strength stainless steel for an elastic substrate of a load sensor, characterized in that the heat-treatment is performed in a heat treatment .

Images