200825187 九、發明說明： 【發明所屬之技術領域】 本鲞明關於一種使用於移動終端或家電製品等之開關 部分的金屬接點（metal dome)用準安定沃斯田系不銹鋼條 之製造方法及其鋼條。 【先前技術】 近年來，因打動電話、個人電腦等電子設備不斷向小 型化發展，故於電氣接點或接觸部分所使用之開關部分的 金屬接點亦不斷向小型化發展。由於即使使金屬接點小型 化，於開關所需之點擊感及耐久性也不會出現較大變化， 結果導致施加於該等小型化開關所使用之材料的應力增 大。因此，對小型化開關之耐久性、φ即材料之疲勞特性 要求更高之性能。 同時滿足良好點擊感以及高耐久性之材料’大多使用 準安定沃斯田系不銹鋼條之SUS301不銹鋼。準安定沃斯 田系不錄鋼，會藉由加工而產生麻田散體式變化 j martensitic transformati〇n )，在材料中生成麻田散體， 藉此貫現高強度化，改善财久性。 強度與疲勞特性之關係，有各種報告，已知會因 測試之模式不同而出現差異，但可發現疲勞強度 伸強度增加而上升，但若超過某固戈之拉伸強度時， 者之關係難以確定（非專利文獻1 )。 另-方面，已知準安定沃斯田系不錄鋼具有下 即，若應力集中於因疲勞而產生之龜裂前4，則該部分會 5 200825187 生成麻田散體而達到高強度，使龜裂難以深入， 優異。控制該準安定沃斯田系不錄鋼之麻田散體量2 去，專利文獻1中揭示有調整壓延速度' 、ϊ 丄 主里、壓ϋ田 油溫度之壓延方法。又，在藉由控制細 ^ 勞特性方面，專利文獻”揭示有控制板厚方向二疲 散體分布量之方法。 之麻田 又，一般金屬材料之疲勞特性改善方法，已知 藉對結晶粒徑進行微細化之處理（非專利文獻0時可 用該方法使平均結晶粒徑在3 盖 ，且使 1工你J μιη以下而改善疲勞 例（專利文獻3)。 废泠特性之 更有包括目前為止所列舉之影響疲勞特性之材 在内’以使材料強度與化學成分、加工誘發麻田散體Γ 關係在一定範圍内之方式進 . -里之 (專利文獻4 )。 性之例 [專利文獻1]日本專利特開2001 - 286904號公報 [專利文獻2]日本專利特開2〇〇4_ 323882號公報 [專利文獻3]日本專利特開2004 - 244725號公報 [專利文獻4]日本專利特開2006- 207005號公報 材料 、[非專利文獻1]越智保雄，「金屬疲勞之基礎」 測試技術，Vol.48，Νο.2，ρ 68 [非專利文獻2]橫掘武夫監譯，「金屬之疲 丸善股份有限公司，1970年6月3日，ρ—W展」， 【發明内容】 根據上述見解來設計疲勞特性優異之不銹鋼條材料 6 200825187 時’可預想到可對結晶 上抑制麻田散體4之產^ ^在某種程度 疲;::工誘發麻田散體量機’而期待更良好之 粒徑二：致力㈣發’得知若對結晶 發麻田散體之產生量ΓΓΓ: ’則必然會導致加工誘 定範圍内。生…，而難以將麻田散體量控制於特 旦專利文獻1中，雖藉由控制壓延條件來控制麻田散體 里’但未對材料之疲勞特性進行研究，又，制專利文獻 揭1之方法時，由於需採用壓延控制所必需之新設備， 5、仃设備改造’因此無法避免製造成本之上升。 專利絲2巾，雖改變最後壓延之加工度、材料之張 、工作輥（work roll)直徑來控制麻田散體量，但並 ^曰曰粒徑進行研究（專利文獻2「觀」）。專利文獻3、 ，亚無考量控制麻田散體量之壓延方法之記載。 本毛明人等為改善材料之疲勞特性，對使結晶粒徑微 、田化且同日$抑制麻田散體量產生之方法進行了各種研究， 結果發現，若使最後壓延前之平均結晶粒徑在5 〇 pm以 、使對其進仃壓延製成製品厚度時之麻田散體量在9〇% 以下，亚使製品厚度上之拉伸強度在1200 MPa以上時， 則可提高疲勞特性。 亦即，本發明係關於（丨）一種疲勞特性優異之準安定 沃斯田系不銹鋼條之製造方法’係對平均結晶粒徑在5.〇_ 7 200825187 以下之材料進行最後冷壓延，使製品厚度上之麻田散體量 在90%以下，獲得拉伸強度在1200 MPa以上之疲勞特性 優異之準安定沃斯田系不銹鋼條；（2 ) —種準安定沃斯 田系不銹鋼條，係由上述（1 )之製造方法所製得；以及 (3 ) —種開關用金屬接點零件，係由上述（2 )之準安定 沃斯田系不錄鋼條構成。 本舍明之準安定沃斯田系不銹鋼條適用於各種電子設 備之開關部分所使用之零件等需要反覆彈性的零件，且適 用於開關用金屬接點零件之疲勞性優異的材料。 【實施方式】 以下說明限定理由。 (1 )最後壓延前之平均結晶粒徑： 马有效改善材料 …，狀力π .- 〜"口的孤徑進行微細200825187 IX. Description of the Invention: [Technical Field of the Invention] The present invention relates to a method for manufacturing a quasi-stabilized Vostian stainless steel strip for a metal dome used in a switch portion of a mobile terminal or a home appliance product, and the like. Its steel bars. [Prior Art] In recent years, electronic devices such as mobile phones and personal computers have been continuously miniaturized, so the metal contacts of the switch parts used in electrical contacts or contact parts have been continuously miniaturized. Even if the metal contacts are miniaturized, the click feeling and durability required for the switches do not largely change, and as a result, the stress applied to the materials used in the miniaturized switches increases. Therefore, the durability of the miniaturized switch, φ, that is, the fatigue characteristics of the material, is required to be higher. At the same time, materials that satisfy the good click feeling and high durability are mostly made of SUS301 stainless steel of quasi-steady Worthian stainless steel strip. The quasi-steady Worth field does not record steel, and it will produce Ma Tian's loose-form change by processing. It will produce Ma Tian's loose body in the material, thereby achieving high strength and improving financial durability. There are various reports on the relationship between strength and fatigue characteristics. It is known that there will be differences due to different test patterns, but it can be found that the fatigue strength increases and increases, but if the tensile strength exceeds a certain strength, the relationship is difficult to determine. (Non-Patent Document 1). On the other hand, it is known that the quasi-stable and stable steels are not recorded, and if the stress is concentrated on the front of the crack due to fatigue, the part will be 5200825187 to form a high-strength, high-strength crack. Difficult to penetrate, excellent. The amount of the loose body of the quarry in the quasi-stable Wostian system is controlled. Patent Document 1 discloses a calendering method of adjusting the calendering speed ', the main crucible, and the temperature of the crucible oil. Moreover, in terms of controlling the characteristics of the fineness of the work, the patent document discloses a method of controlling the distribution amount of the two layers of the fatigue in the thickness direction of the plate. In addition, the method for improving the fatigue characteristics of the general metal material is known by the crystal grain size. The process of miniaturization (When the non-patent document 0 is used, this method can be used to make the average crystal grain size of 3 caps, and it is possible to improve the fatigue by the work of 1 μm or less. (Patent Document 3). In the case of the material that affects the fatigue characteristics, the relationship between the strength of the material and the chemical composition and the processing of the granules in the field is within a certain range. - Lido (Patent Document 4). Examples of Sex [Patent Document 1] Japan [Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-244725 (Patent Document 4) Japanese Patent Laid-Open No. 2006- 207005 No. Bulletin Material, [Non-Patent Document 1] Kichihiko Kazuo, "Basic of Metal Fatigue" Test Technology, Vol.48, Νο.2, ρ 68 [Non-Patent Document 2] Cross-Excavation, "Fighting of Metals Co., Ltd., June 3, 1970, ρ-W Exhibition", [Disclosed] According to the above findings, the design of stainless steel strip material 6 with excellent fatigue characteristics is considered to be able to inhibit the production of Ma Tian's bulk 4 on the crystal. ^ ^In some degree of fatigue;::Working induces Ma Tian's bulk measuring machine' and expecting a better particle size 2: Dedication (4) Hair 'learning about the amount of crystallization of the numbness of the field ΓΓΓ: 'There will inevitably lead to processing incentives Within the range of ...., it is difficult to control the amount of Ma Tian's bulk in the patent document 1 of the Tetan, although the control of the calendering conditions to control the Ma Tian bulk" but did not study the fatigue characteristics of the material, but also the patent literature In the method of 1, the new equipment necessary for the calendering control is required, and the equipment is modified. Therefore, the increase in manufacturing cost cannot be avoided. The patented silk 2 towel changes the degree of processing of the final calendering, the sheet of material, and the work roll. (work roll) diameter to control the amount of granules in the field, but to study the particle size (Patent Document 2 "View"). Patent Document 3, the sub-measurement of the method of controlling the amount of granules in the field In order to improve the fatigue characteristics of the material, the present Maoming et al. conducted various studies on the method of making the crystal grain size micro, fielding, and suppressing the amount of the mass of the field in the same day. As a result, it was found that the average crystal grain before the final rolling was obtained. When the diameter is 5 〇 pm, the amount of the granules of the granules is less than 9〇% when the thickness of the product is rolled into a product. When the tensile strength of the product is 1200 MPa or more, the fatigue characteristics can be improved. That is, the present invention relates to a method for producing a quasi-stable Vosfield stainless steel strip having excellent fatigue characteristics, which is to carry out final cold rolling of a material having an average crystal grain size of 5. 〇 _ 7 200825187 or less to make a product thickness. The amount of the loose body in the Ma Tian is below 90%, and the quasi-stable Worthian stainless steel strip with excellent tensile properties with tensile strength above 1200 MPa is obtained; (2) the quasi-steady Worthian stainless steel strip is composed of the above ( 1) The method of manufacturing the method; and (3) the metal contact part for the switch, which is composed of the quasi-stable Woosfield unrecorded steel strip of the above (2). BenQing's quasi-stabilized Vostian stainless steel strips are suitable for parts that require resilience, such as parts used in the switch parts of various electronic equipment, and are suitable for materials with excellent fatigue properties of metal contact parts for switching. [Embodiment] The reason for limitation is described below. (1) Average crystal grain size before final rolling: Horse effective improvement material ..., force force π .- ~"
化。其原因在於，疲勞初期產生之龜裂於結晶粒内擴散時， 晶界具有阻止龜裂擴散之障礙物的作用。於實際的製品， 係在再結晶退火後實施壓延加卫，壓延前之平均結晶粒徑 越微細則壓延後結晶粒界所占之比例越多，對改善疲勞： 性越有效。亦即，若於最後壓延前之再結晶退火步驟中^ 對結晶粒徑進行微細化後實施最後壓延， 4里缺t 、』」獲件良好的 “''、、、而，如本發明之課題所述’ 一邊對結晶粒 微細化，一邊進而控制麻田散體量，藉此可進—牛 勞特性’ il此，考慮到與麻田散體量之平衡而對最：σ疲 均結晶粒徑之範圍進行了各種研究。結果 之平 延前之平均結晶粒徑在5·〇 μιη以下時，疲最後壓 屣喊特性獲得顯著 8 200825187 改善。本發明之效I女 得。若平均結32^：5^_狀料結晶粒徑中獲 σ ·0 μιη，則會導致疲勞特性下降。 (2 )麻田散體量： 準安定沃斯田季π錄〜 …歹一 糸不銹鋼，由於應力集中於因疲勞所產 生之龜裂两端，故該部八 文“分生成麻田散體而高強度化，因此 龜衣難以發展，疲答姓 旦 义。對影響疲勞特性之麻田散體 里進订了各種研究，社果 ,ΟΛΟ/. , 、、°果發現，當製品厚度之麻田散體量Chemical. This is because when the crack generated in the initial stage of the fatigue is diffused in the crystal grain, the grain boundary has an action of preventing the crack from spreading. In the actual product, calendering is carried out after recrystallization annealing, and the average crystal grain size before rolling is more precise. The more the proportion of crystal grain boundary is, the more effective it is to improve fatigue: That is, if the crystal grain size is refined in the recrystallization annealing step before the final rolling, and then the final rolling is performed, the missing "," in the case of "there is a good", as in the present invention. According to the subject, while the crystal grains are refined, and the amount of the granules is controlled, the yoghurt characteristics can be improved. In view of the balance with the amount of granules, the range of σ Various studies have been carried out. When the average crystal grain size before the flattening is below 5·〇μηη, the fatigue final screaming characteristic is significantly improved by 2008. The effect of the present invention is 1. If the average knot is 32^:5 If σ · 0 μηη is obtained in the crystal grain size of ^_, the fatigue characteristics will be reduced. (2) The amount of loose powder in Ma Tian: Quasi-steady Worthian season π recorded ~ ... 歹 糸 stainless steel, due to stress concentration due to fatigue The two ends of the crack, so the Ministry of the eight articles "divided into the Ma Tian bulk and high strength, so the turtle suit is difficult to develop, fatigue and surname. Various studies have been made in the field of Ma Tian, which affects the fatigue characteristics, and the results of the fruit, ΟΛΟ/., ,, °, and the amount of granules in the thickness of the product
在90/以下吟，疲勞 則應力集中之部分不獲；^者改善。若超過㈣， 勞強度變差。 曰成麻田散體，導致龜裂發展，疲 廚田政體里之控制’除上述平均結晶粒徑之控 制外，由於Μ延加卫時之難用油溫度亦有較強之影響， 因此，必須根據平均結絲徑、壓延加工度而適當地設定、 控制壓延用油溫度。 (3 )拉伸強度 由本發明之製造方法所得之準安定沃斯田系不銹鋼條 …伸強度車乂乜在12〇〇 MPa以上。若未滿^猜&則 播法獲得充分之疲勞特性。 [實施例] 購置SUS301不銹鋼（板厚為15 mm，固溶處理材料）， 乂 50/以上之加工度實施冷壓延後，使用連續退火爐，使 爐溫在120(TC以下，材料之爐内滯留時間為12()秒以下， 將平均結晶粒徑調整為5〇 μιη以下。並且，U 5Q%以上 之加工度對該材料進行冷壓延，以與上述相同之方式，在 9 200825187 爐溫及爐内滯留時間經調整的爐内進行再結晶退火以使平 均結晶粒在5.0 μπι以下，然後，實施最後冷壓延至板厚為 60 μηι為止。上述平均結晶粒徑在5·〇 μηι以下之再結晶退 火之爐溫及爐内滯留時間，於例如板厚為〇1 mm時，為 950°C〜1050°C及9〜14秒。在最後冷壓延中，根據平均結 晶粒徑之大小，將壓延加工度於4〇〜6〇%之範圍内，壓延 用油溫度於4(TC〜60。〇之範圍内進行調整組合，藉此將板 厚為60 4瓜時之麻田散體量調整為9〇%以下。將所得製品 作為受測材，測量機械特性，使用薄板帶壽命測試機實^ 疲勞測試，並且測量麻田散體量。以下詳述該等材料特性 之評價方法。 ^ 1 )平均結晶粒徑： 直接進行電解研磨藉此將壓延面精加工為鏡面，電解 …：使用過虱酉夂與乙醇以1 : 4之體積比混合所得之 /谷液，將樣品作為陽極進行通電。 使用FE-SEM (場私斛荆戸以^ 解研磨彳^電子顯微鏡），觀察電 2內 '"面’根據結晶之大小測量4.5χ1〇-3〜2.5χ1〇·2 mm2内之么士日私工at 1 υ 據一 晶粒徑。結晶粒徑之評價係根 所規疋之切斷法實施。 (2)麻田散體（Ms)量： 麻田散體量，係、刹田4 ^ 散體相則為順磁性，、·此二：：斯田相之非磁性，麻田 鐵分析儀）測量材料之磁 ^1肥粒鐵含量計（肥粒 量，具體由俨又，由變態為麻田散體量之 ，、販田體積率未得。 再者，測I中，將鐵磁體之純 10 200825187 麻田散體量設為i00%，將相對於該純Ni麻田散體量之相 對值作為麻田散體量（％)。 (3)機械特性（拉伸強度）： 對依照JIS z 2201所規定之13B號標準之板狀測試片 進行衝壓，依照jIS Z 2241標準實施拉伸測試。 (4 )疲勞特性： 疲勞特性，係將材料加工為金屬接點來進行確認。亦At 90/s or less, fatigue is not concentrated in the stress concentration; If it exceeds (4), the labor intensity will deteriorate.曰成麻田散体, resulting in the development of cracks, the control of the tired kitchen field body 'In addition to the above control of the average crystal grain size, because the temperature of the hard-to-use oil during the extension of the Guardian has a strong influence, therefore, must be based on The rolling oil temperature is appropriately set and controlled in accordance with the average knot diameter and the rolling degree. (3) Tensile strength The quasi-steady Worthian stainless steel strip obtained by the production method of the present invention has a tensile strength of more than 12 MPa. If not guessed & then the broadcast method obtains sufficient fatigue characteristics. [Examples] SUS301 stainless steel (15 mm thick, solution treated material) was purchased, and the degree of processing of 乂50/above was subjected to cold rolling, and a continuous annealing furnace was used to set the furnace temperature to 120 (TC or less, in the furnace of the material). The residence time is 12 (sec) or less, and the average crystal grain size is adjusted to 5 μm or less. Further, the material is cold-rolled at a processing degree of U 5Q% or more, in the same manner as described above, at a temperature of 9 200825187 The furnace in the furnace is subjected to recrystallization annealing in an adjusted furnace so that the average crystal grain is below 5.0 μπι, and then finally cold-rolled to a thickness of 60 μηι. The average crystal grain size is less than 5·〇μηι. The temperature of the furnace for crystallization annealing and the residence time in the furnace are, for example, 950 ° C to 1050 ° C and 9 to 14 seconds when the sheet thickness is 〇 1 mm. In the final cold rolling, according to the average crystal grain size, The calendering degree is in the range of 4 〇 to 6 〇%, and the temperature of the rolling oil is adjusted and combined in the range of 4 (TC 〜 60 〇 〇 , , , , , , 调整 调整 调整 调整 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 〇% or less. The obtained product is used as the material to be tested. The mechanical properties were measured, and the fatigue test was performed using a thin-plate life tester, and the amount of loose matter in the field was measured. The evaluation method of the properties of the materials was detailed below. ^ 1) Average crystal grain size: Directly performing electrolytic grinding to thereby roll the surface Machining into a mirror, electrolysis...: Using a mixture of ruthenium and ethanol in a volume ratio of 1: 4, the sample is used as an anode for energization. Using FE-SEM (Field 斛 戸 戸 ^ ^ ^ 彳 彳 彳^ Electron microscope), observe the '2' inside the '2' according to the size of the crystal. 4.5χ1〇-3~2.5χ1〇·2 mm2 in the 么士日私工 at 1 υ according to the crystal grain size. Crystal grain size The evaluation is carried out by the method of cutting off the roots. (2) The amount of Ma Tian's bulk (Ms): The amount of Ma Tian's loose body, the department, the 4-4 of the Shatian field is paramagnetic, and the second:: Shi Tianxiang Non-magnetic, Ma Tian iron analyzer) measuring the magnetic content of the material ^ 1 fat iron content meter (fertilizer amount, specifically from 俨 ,, from the metamorphosis to the amount of granulated bulk, the volume of the field is not available. Again, test I In the middle, the ferromagnetic pure 10 200825187 Ma Tian volume is set to i00%, will be relative The relative value of the volume of the pure Ni Ma field is referred to as the amount of the lost volume of the field (%). (3) Mechanical properties (tensile strength): The plate-shaped test piece according to the 13B standard specified in JIS z 2201 is punched according to jIS Z The 2241 standard is subjected to tensile testing. (4) Fatigue characteristics: Fatigue characteristics are determined by processing the material into metal joints.
即，將材料加工成直徑為4.〇 mm之金屬接點以使操作負 戴為2.0±0_2 N，以500 gf之負载' 3次/秒之速度使金屬 接點反覆開關300萬次。將各種材料的每—種分別加工成 〇们五屬接點，將上述開關測試中5個以上金屬接點產生 裂痕的開關記作「X」，產生裂痕之數…〜4個時記 作「△」’產生裂痕之數目在丄個以下時記作「◦」。 表1表示發明例。 [表1]That is, the material was machined into a metal contact having a diameter of 4. 〇 mm so that the operation was negatively worn as 2.0 ± 0 2 N, and the metal contact was repeatedly switched 3 million times at a load of 3 g/s at a load of 500 gf. Each of the various materials is processed into five joints, and the switch that cracks more than five metal contacts in the above switch test is recorded as "X", and the number of cracks is generated...~4 is recorded as " △"' The number of cracks is recorded as "◦" when it is less than one. Table 1 shows an inventive example. [Table 1]
200825187 表2表示比較例。 【表2] 實施例 結晶粒徑 (μπι) 壓延加工度, (%) 歷延用油溫度 (°C) Ms量 (%) 拉伸強度 (MPa) 疲勞特性 11 11.2 50 40 40 1465 X 12 5.7 50 40 51 1509 X 13 2.2 50 30 91 1696 __Δ 14 2.2 60 40 94 1804 X 15 2.2 68 60 92 1849 X 16 1.4 10 40 22 1105 X 17 1.4 45 40 95 1618 X 18 1.4 60 50 94 1767 X 1 C ^ 0.6 10 60 33 1187 [Ζδ~~ 實施例1〜10及實施例A、B，最後壓延前之平均結 晶粒徑在5·0 μπι以下，麻田散體量在9〇%以下，且拉伸 強度在1200 MPa以上，金屬接點加工後之疲勞測試中，^ 〇 個金屬接點中產生裂痕之數在1個以下，疲勞特性良好。 另一方面，比較例11、12中，麻田散體量在9〇%以 下，拉伸強度在UOO MPa以上，壓延加工度及壓延用油 溫度與實施例2、4相同，但最後壓延前之平均結晶粒徑 超過5·〇 μιη，因而疲勞特性較實施例差。 比較例13、14，最後壓延前之平均結晶粒徑在 以下，拉伸強度在测跑以上，且比較你"3之壓延加 工度與實施例4相同，Χ，比較例14之壓延加工度與實 施例5相同，但壓延用油溫度均低於實施例，冑田散體二 超過90%，故疲勞特性較實施例差。 12 200825187 比較例15，最後壓延前之平均結晶粒徑及最後壓延時 之壓延用油溫度與實施例6相同，且最後壓延前之平均結 晶粒徑在5.0 μπι以下，拉伸強度在1200 MPa以上，但壓 延加工度高，且麻田散體量超過90%，故疲勞特性較實施 例差。 比較例16及C，最後壓延前之平均結晶粒徑在5 〇 μιη 以下，且麻田散體量在90%以下，但拉伸強度未滿12〇〇 MPa，故疲勞特性較實施例差。 比較例17 ' 18，最後壓延前之平均結晶粒徑在5 〇 μιη 以下，且拉伸強度在12〇0 MPa以上，比較例17之壓延加 工度與實施例8相同但壓延用油溫度低，又，比較例18 之壓延用油溫度與實施例8、9相同但壓延加工度高，因 此，麻田散體量均超過90%，疲勞特性較實施例差。 【圖式簡單說明】 (無） 【主要元件符號說明】 (無） 13200825187 Table 2 shows a comparative example. [Table 2] Example Crystal grain size (μπι) Calendering degree, (%) Oil temperature (°C) Ms amount (%) Tensile strength (MPa) Fatigue property 11 11.2 50 40 40 1465 X 12 5.7 50 40 51 1509 X 13 2.2 50 30 91 1696 __Δ 14 2.2 60 40 94 1804 X 15 2.2 68 60 92 1849 X 16 1.4 10 40 22 1105 X 17 1.4 45 40 95 1618 X 18 1.4 60 50 94 1767 X 1 C ^ 0.6 10 60 33 1187 [Ζδ~~ Examples 1 to 10 and Examples A and B, the average crystal grain size before calendering is below 5.00 μπι, the amount of Ma Tian bulk is below 9〇%, and the tensile strength is In the fatigue test after machining of metal contacts at 1200 MPa or more, the number of cracks in one metal joint is less than one, and the fatigue characteristics are good. On the other hand, in Comparative Examples 11 and 12, the amount of the granules was 9% or less, the tensile strength was UOO MPa or more, and the calendering degree and the temperature of the rolling oil were the same as those of Examples 2 and 4, but the average before the final rolling. Since the crystal grain size exceeds 5·〇μηη, the fatigue characteristics are inferior to those of the examples. In Comparative Examples 13 and 14, the average crystal grain size before the final calendering was below, the tensile strength was above the run, and the calendering degree of the comparison was the same as in Example 4, Χ, the calendering degree of Comparative Example 14 The same as in the fifth embodiment, but the temperature of the rolling oil was lower than that of the examples, and the volume of the powder of the field was more than 90%, so the fatigue characteristics were inferior to those of the examples. 12 200825187 Comparative Example 15, the average crystal grain size before final rolling and the temperature of the rolling oil for the final rolling delay were the same as in Example 6, and the average crystal grain size before final rolling was 5.0 μπι or less, and the tensile strength was 1200 MPa or more. However, the degree of calendering processing is high, and the amount of the loose body in the field is more than 90%, so the fatigue characteristics are inferior to the examples. In Comparative Examples 16 and C, the average crystal grain size before rolling was 5 〇 μηη or less, and the amount of granules in the field was 90% or less, but the tensile strength was less than 12 MPa, so the fatigue characteristics were inferior to those in the examples. Comparative Example 17 '18, the average crystal grain size before the final rolling was 5 〇μηη or less, and the tensile strength was 12 〇0 MPa or more, and the rolling workability of Comparative Example 17 was the same as that of Example 8, but the rolling oil temperature was low. Further, the temperature of the rolling oil of Comparative Example 18 was the same as that of Examples 8 and 9, but the rolling workability was high. Therefore, the amount of the mass of the field was more than 90%, and the fatigue characteristics were inferior to those of the examples. [Simple description of the diagram] (none) [Description of main component symbols] (none) 13