Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0236—Cold rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/008—Martensite
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H2201/00—Contacts
  • H01H2201/022—Material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H2205/00—Movable contacts
  • H01H2205/016—Separate bridge contact
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the present invention relates to a method for producing a metastable austenitic stainless steel strip for a metal dome used for a switch portion of a portable terminal, a home appliance, or the like, and the steel strip.
• SUS301 stainless steel which is a metastable austenitic stainless steel strip
• martensitic transformation occurs during processing, and martensite is generated in the material, resulting in higher strength and improved durability.
• Patent Document 1 discloses a rolling method in which the rolling speed, the reduction amount, and the rolling oil temperature are adjusted. Regarding the improvement of fatigue characteristics by controlling the amount of martensite, the distribution of martensite in the thickness direction is controlled. This method is disclosed in Patent Document 2.
• Non-patent Document 2 a general method for improving the fatigue properties of metal materials may be possible by reducing the crystal grain size.
• Patent Document 3 There is an example in which fatigue characteristics are improved by setting the average grain size to 3 im or less.
• Patent Document 4 examples of improved fatigue characteristics by adjusting the relationship between the strength of the material, the chemical composition, and the amount of work-induced martensite within a certain range.
• Patent Document 1 Japanese Patent Laid-Open No. 2001-286904
• Patent Document 2 JP 2004-323882 Koyuki
• Patent Document 3 Japanese Patent Application Laid-Open No. 2004-244725
• Patent Document 4 Japanese Unexamined Patent Publication No. 2006-207005
• Non-Patent Literature 1 Yasuo Ochi, “Fundamentals of Metal Fatigue”, Material Testing Technology, Vol. 48, No. 2, p. 68
• Non-Patent Document 2 Translated by Takeo Yokobori, "Fatigue fracture of metals", Maruzen Co., Ltd., June 3, 1970, p. 32-39
• Patent Document 1 does not examine the fatigue characteristics of a force material in which the amount of martensite is controlled by controlling rolling conditions.
• an increase in manufacturing cost is inevitable because it involves the introduction of new equipment necessary for rolling control or modification of equipment.
• Patent Document 2 the degree of martensite is controlled by changing the workability of the final rolling, the material tension, and the work roll diameter! /, But the crystal grain size! / Is conscious! , Na! / ⁇ (Patent Document 2 “0018”).
• Patent Documents 3 and 4 do not describe a rolling method considering the control of the martensite amount.
• the present inventors have determined that the average crystal grain size before final rolling is 5. It was found that the fatigue characteristics were improved when the martensite content was 90% or less and the tensile strength in the product thickness was 1200 MPa or more when O ⁇ m or less was rolled to obtain the product thickness.
• the present invention provides:
• a material with an average crystal grain size of 5. O ⁇ m or less is finally cold-rolled to a martensite content of 90% or less at the product thickness, and has excellent fatigue properties with a tensile strength of 1200 MPa or more.
• a method for producing a stable austenitic stainless steel strip
• the metastable austenitic stainless steel strip of the present invention is suitable for parts that require repeated springiness, such as parts used in switch parts of various electronic devices, and is suitable for metal dome parts for switches. It is a material with excellent characteristics.
• the fatigue properties are further improved by further reducing the grain size and further controlling the martensite amount, so that the optimum average considering the balance with the martensite amount is taken into account.
• the tensile strength of the metastable austenitic stainless steel strip obtained by the production method of the present invention is preferably 1200 MPa or more. If it is less than 1200 MPa, sufficient fatigue characteristics cannot be obtained.
• the furnace temperature and residence time of the recrystallization annealing in which the average crystal grain size becomes 5. ⁇ or less are, for example, 950 ° C to 1050 ° C for a plate thickness of 0.1 mm, and 9 to 14 seconds for 1050 ° C. It is.
• the rolling thickness is adjusted to 40 to 60%, and the temperature of the rolling oil is adjusted appropriately in the range of 40 to 60 ° C to combine the thickness 60 Adjust the martensite content in m to 90% or less. Using this as a test material, mechanical properties, fatigue tests using a thin belt life tester, and the amount of martensite were measured. These material property evaluation methods are described in detail below.
• the rolled surface was directly polished and finished into a mirror surface.
• electropolishing a solution in which perchloric acid and ethyl alcohol were mixed at a volume ratio of 1: 4 was used, and the sample was used as an anode to conduct electricity.
• the martensite content is based on the fact that the martensite phase is paramagnetic while the austenite phase is non-magnetic, so that the magnetic strength of the material can be measured using a magnetic induction ferrite content meter (ferrite scope). By measuring, the amount of transformation to the amount of martensite, specifically, the volume ratio was obtained. In the measurement, the martensite content of pure Ni, which is a ferromagnetic material, was 100%, and the relative value to this was the martensite content (%).
• a plate-shaped test piece conforming to No. 13B defined in JIS Z 2201 was punched out, and a tensile test conforming to JIS Z 2241 was performed.
• the fatigue test was confirmed by processing the material into a metal dome. That is, operating load 2.0 soil It was processed into a metal dome with a diameter of 4. Omm to 0. 2N, and switched repeatedly to 3 million times at a load of 500gf and a speed of 3 times / second. 10 pieces of various materials are processed into metal dome one by one, the switch where 5 or more cracks occurred in the above switching test is “X”, the number of cracks 2 to 4 is “ ⁇ ”, and the number of cracks is 1 or less. “Yes”.
• a comparative example is shown in Table 2.
• Comparative Examples 13 and 14 had an average crystal grain size before final rolling of 5.0 111 or less and a tensile strength of 120 OMPa or more, Comparative Example 13 was Example 4, and Comparative Example 14 was Example 5. Although the degree of rolling process is the same, the fatigue properties are inferior to those of the examples because the martensite content at which the rolling oil temperature is lower than that of the examples exceeds 90%.
• the average crystal grain size before final rolling and the rolling oil temperature in the final rolling are the same as in Example 6, the average crystal grain size before final rolling is 5. ⁇ or less, and the tensile strength is 1 Strength of 200 MPa or more The amount of martensite with high rolling workability exceeds 90%, so the fatigue properties are inferior to the examples.
• the average crystal grain size before final rolling is 5. O ⁇ m or less and the amount of martensite is 90% or less, but the tensile strength is less than 1200 MPa. Fatigue properties are inferior.
• Comparative Examples 17 and 18 the average crystal grain size before final rolling is 5. O ⁇ m or less, the tensile strength is 12 OOMPa or more, and Comparative Example 17 has the same rolling work degree as Example 8, but the rolling oil The temperature is low.
• Comparative Example 18 has the same rolling oil temperature as Examples 8 and 9, but the degree of rolling process is high, so both have a martensite content of over 90%. Inferior fatigue properties

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Push-Button Switches (AREA)
• Contacts (AREA)
• Heat Treatment Of Steel (AREA)

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Citations (4)

• 2007
  • 2007-09-28 CN CNA200780035431XA patent/CN101517101A/zh active Pending
  • 2007-09-28 WO PCT/JP2007/069009 patent/WO2008041638A1/ja active Application Filing
  • 2007-09-28 TW TW96136107A patent/TW200825187A/zh unknown
  • 2007-09-28 JP JP2008537513A patent/JPWO2008041638A1/ja not_active Abandoned
  • 2007-09-28 KR KR20097002877A patent/KR20090039764A/ko not_active Application Discontinuation

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