Casting - Imono (English spelling)

Japanese: 鋳物 - いもの（英語表記）casting

This refers to metal products (castings) made by pouring molten metal into a mold with a cavity corresponding to the shape of the desired product and allowing it to solidify as is (casting method). In addition to castings, metal products include forged products (forged products) and rolled products, which are made by forging or rolling a type of casting called an ingot that has been cast into a simple shape, and welding these together. Compared to forged and rolled products, castings have a coarser crystal structure, can contain segregation of components (uneven solidification) and voids (voids), and are brittle. However, castings are easy to mass-produce in complex shapes, so they are widely used as durable consumer goods such as automobiles and other machine parts.

[Katsuya Igawa and Zenshiro Hara]

The origins of casting

The origin of casting dates back to the late Neolithic period, when temperatures of over 1000°C, enough to melt gold and copper, could be achieved in kilns used to fire pottery. The oldest casting is probably a bronze axe from 4500 BC, discovered in the upper reaches of the Mekong River. In the Middle East, copper axes began to be cast in open stone molds between 4000 and 3500 BC, and when bronze began to be smelted between 3000 and 2500 BC, the technique of casting bronze tools with holed handles in a core-fitted mold spread to Europe. In China, a bronze culture was born in the middle reaches of the Yellow River around 1700 BC, and by the Shang dynasty, the technique of casting ritual vessels of various shapes with complex patterns and beautiful cast surfaces had been acquired using molds made from pieces of fired clay. Following bronze, iron-making technology was developed in the Near East between 1500 and 1000 BC, and iron smelting began in China around 400 BC. Cast iron technology emerged soon after, and by 100 BC cast iron agricultural tools were being mass-produced (however, in Europe cast iron production did not begin until the 14th century).

Bronze and iron tools were brought to Japan from the continent around 300 BCE, and the casting of bronze swords and bronze bells using imported bronze raw materials in stone molds with cores began around 100 BCE. Iron production in Japan began around 400 BCE, but cast iron casting did not begin until after the re-import of casting techniques following the introduction of Buddhism (6th century).

[Katsuya Igawa and Zenshiro Hara]

The development of the Japanese foundry industry

New casting techniques that were introduced from the continent along with Buddhism included (1) the combination casting method, (2) the wax casting method, and (3) the cast casting method, which used a mixture of clay called mane and sand as the mold material. From the 7th to 8th centuries, the Great Buddha of Asuka and the Great Buddha of Nara were made using (1), the Amida Triad at Horyu-ji Temple and the Buddhas at Shin-Yakushi-ji Temple were made using (2), and the nine-wheeled pagodas and temple bells at various temples were made using (3). The Great Buddha of Nara is the largest casting in the world. Under the Ritsuryo system, these casting techniques were passed down in various government-run workshops in the Kinki region, but in the Heian period, they also spread to workshops affiliated with provincial offices and manors, and bronze temple bells, Buddhist altar implements, mirrors, cast iron lanterns, pots, and kettles began to be produced in various places. At the end of the Heian period, these workshops stopped being directly managed, and artisan families began to operate independently on the condition that they paid annual taxes. For example, a group of foundries in Tannan, Kawachi Province (Mihara Ward, Sakai City, Osaka Prefecture) were allowed to produce and sell pots and kettles nationwide as lantern offerings to the Kurodo-dokoro (Kurodo-dokoro). Casting techniques spread further when Tannan casters who participated in the casting of the Great Buddha of Kamakura settled in the eastern part of the country, and in the Muromachi period, caster settlements called Kanaya were established in various places, and in the Edo period, in addition to Edo and Kyoto, Sano, Yamagata, Mizusawa, Kawaguchi, Kuwana, and Takaoka flourished as casting production centers. These formed the basis for industrial modernization in the Meiji period.

At the end of the Edo period, the shogunate and various feudal domains focused on casting cannons and building warships, and Western-style blast furnaces were put into operation in Kamaishi and Kagoshima, and cast iron guns were cast using reverberatory furnaces in Saga and Nirayama. These were made possible by knowledge from Dutch technical books and domestic technology. The Nagasaki Shipyard and Yokosuka Shipyard, which the shogunate opened with technical assistance from the Netherlands and France, respectively, popularized the dry mold molding method and green sand mold molding method for machine casting throughout the country.

The Meiji government took over this tradition, and excellent casting techniques were developed at the Navy's Yokosuka, Kure, Sasebo, and Maizuru Arsenals, which would later lead the private sector in casting techniques. The number of private shipyards also increased during the Meiji period, and in addition to shipbuilding, they expanded into land-use boilers, land-use steam engines, mining machinery, bridges, and other fields, diversifying the types of casting products. Furthermore, large private factories were established to make cast iron pipes for water supply and sewage systems, which were necessary for the modernization of cities.

From the mid-Meiji period to the 1930s, the foundry industry developed greatly in line with the growth of the nation's power. At this time, a dual structure was created between the large companies that emerged from the end of the Edo period to the Meiji period, and the traditional foundry production areas, with the latter acting as subcontractors for the former, supporting each other and contributing to the development of the foundry industry. This was also the period when the academic fields that form the basis of foundry technology, such as metallurgical engineering, mechanical engineering, and chemical engineering, developed, and foundry technology developed further with the academic foundations of metal materials for casting, mold materials and molding methods, and mold design.

[Katsuya Igawa and Zenshiro Hara]

Types and developments of castings

Castings can be classified by material into cast iron castings, steel castings, copper alloy castings, and light alloy castings.

[Katsuya Igawa and Zenshiro Hara]

Cast Iron Castings

With the spread of cupolas as melting furnaces, the use of coke as fuel, and the use of electric fans for ventilation, the melting amount, melting speed, and melting temperature of cast iron castings improved significantly. It was discovered that the properties of cast iron could be changed in various ways by adjusting the amounts of carbon, silicon, and manganese, and it was discovered that by mixing pig iron and scrap steel, cast iron castings with a so-called chrysanthemum grain structure, in which flake graphite is uniformly distributed in a pearlite base, could be obtained, and it was found that this material was highly wear-resistant and had high tensile strength, making it suitable for machine parts. In addition, cast iron was melted in a reverberatory furnace, its composition was carefully adjusted, and it was then cast into a mold with a metal die attached to the inside to harden the surface of the casting, resulting in the successful production of rolls using chilled casting, and these rolls were widely used for rolling steel. Furthermore, at the end of the Meiji period, they succeeded in producing malleable iron castings. By annealing white iron castings, they were able to obtain extremely ductile cast iron, which could be used as iron pipe fittings to meet the huge demand caused by the spread of water supply systems.

[Katsuya Igawa and Zenshiro Hara]

Steel Castings

Steel castings have high melting temperatures and large solidification shrinkage, so they are prone to shrinkage cavities, pinholes, and other voids, and require advanced casting techniques. During the Meiji period, open hearth furnaces were mainly used for melting, but the melting time was long and the temperature was insufficient, making it difficult to obtain good quality products. In the Taisho period, the first Héroult electric arc furnaces were introduced, and good quality cast steel products began to be produced.

[Katsuya Igawa and Zenshiro Hara]

Copper alloy castings

Copper alloy castings are melted in a crucible furnace, and bronze, which is 88% copper, 10% tin, and 2% zinc, is the most commonly used, also known as gunmetal. Copper alloys are highly resistant to corrosion, seawater, and tough, so they are widely used in ships. In that sense, the navy actively researched them, and from around 1905 (Meiji 38), manganese brass, which is 40% zinc, 5% manganese, and 1% aluminum or less, replaced bronze as a material for ship propulsion equipment, and then, in the Showa era, silzin bronze, which is 10 or 15% zinc and 4% silicon, began to be used.

[Katsuya Igawa and Zenshiro Hara]

Light alloy castings

Light alloy castings, both aluminum and magnesium, began to be manufactured in the Showa era. Aluminum alloys for casting include nickel-containing Y alloy, silicon-containing silumin, copper-containing lautal, and magnesium-containing corrosion-resistant hydronalium, each of which was used according to its own characteristics as the aircraft industry developed.

On the other hand, magnesium alloys were made from aluminum, or alloys of aluminum with zinc or manganese, but they were easily oxidized when melted and the molds also required measures to prevent oxidation, so the widespread use of magnesium alloy castings did not progress easily.

Additionally, in the 1930s, aluminum alloy die casting (a method of forcing molten alloy into a mold and allowing it to solidify) also became very popular.

Thus, Japan's industry, and in particular the foundry industry, which had developed from the mid-Meiji period through the 1930s, came to a complete halt for a while after the end of World War II and Japan's defeat. However, the economy grew remarkably thereafter, and casting production, which was just under one million tons in 1950 (Showa 25), rose to eight million tons in 1973, and was still above seven million tons in 1980.

Since then, production has remained almost flat, reaching 6.88 million tons in 2006.

[Katsuya Igawa and Zenshiro Hara]

Manufacturing Innovation

As for cast iron castings, spheroidal graphite cast iron was invented. This eliminated the weakness of cast iron, which was brittle, and it began to be used for strength components. It is widely used for automobile crankshafts and cast iron pipes that can withstand high loads. Low-frequency induction furnaces also came to be used to melt cast iron, making it possible to obtain molten cast iron by carburizing scrap steel, and making it easier to control the composition and temperature, and to maintain the molten metal.

In the field of steel casting, theoretical elucidation is being advanced to create sound castings by using computers for the design of casting methods and risers.

In the field of copper alloys, aluminum bronze, which contains 10% aluminum, is growing in popularity as a material for ship propulsion engines.

In the area of light alloy casting, aluminum die casting has shown particularly remarkable growth. Silumin alloys containing 10% silicon are used. In addition, high-purity zinc ingots have become readily available due to improvements in refining technology, so zinc die casting, which was previously brittle and unusable due to impurities such as lead and cadmium, is now widely used.

It is no exaggeration to say that the production efficiency of casting factories is determined by mold manufacturing technology. Until the Second World War, molds were limited to those made by mixing silica sand with clay and water, but since then, a countless number of new molding methods have been developed one after another. The shell molding method uses phenolic resin as a binder, and since the organic matter used as the binder is thermally decomposed and loses its binding power after casting, it is very easy to regenerate the casting sand. Next, the carbon dioxide molding method uses water glass as a binder and blows in carbon dioxide gas to cause a reaction and harden in a short time, which gives the mold great strength and has become popular as an alternative to dry molding. The V process method, which uses a polyvinyl chloride membrane to create a vacuum inside the sand mold and hardens the mold by external pressure, is a molding method invented in Japan that does not use any binder at all and has attracted attention worldwide.

However, the traditional green sand molding method, in which casting sand is bonded with clay and moisture, is easy to mold and inexpensive, and as green sand molding machines have become faster, higher pressure, and larger, it still dominates the molding method today.

The wax casting method, which dates back to the Nara period, is being revived as a method for producing precision castings. This is called the lost wax method, and involves creating a wax model using a precision mold, embedding this in a muddy mixture of refractory powder and ethyl silicate solution, and then drying and baking to melt the wax and create a mold. This method is applied to the production of parts with complex curved surfaces, such as turbine blades, which are difficult to produce using other processing methods, and special alloy parts that cannot be processed by plastic processing or cutting.

[Katsuya Igawa and Zenshiro Hara]

[Reference] | Foundryman | Spheroidal graphite cast iron | Casting

Tsukiji Reverberatory Furnace
Saga City, Saga Prefecture © Saga Tourism Federation

Tsukiji Reverberatory Furnace

Nirayama Reverberatory Furnace
This reverberatory furnace was built in Nirayama by Izu magistrate Egawa Hidetatsu at the end of the Edo period to cast cannons. The heat from the furnace was reflected by the arched ceiling of firebricks to melt the iron. The chimney is 16m high. It is the only reverberatory furnace in Japan that remains almost intact. Nationally designated historic site Part of the World Heritage Site "Sites of Japan's Meiji Industrial Revolution: Iron and Steel, Shipbuilding, and Coal Mining" (registered in 2015) Izunokuni City, Shizuoka Prefecture © Shizuoka Prefecture Tourism Association ">

Nirayama Reverberatory Furnace

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

目的製品の形状に対応した型穴をもつ鋳型に溶融金属を注入し、そのまま凝固させるという方法（鋳造法）で製作した金属製品（鋳造品）をいう。金属製品には鋳物のほかに、簡単な形状に鋳造した鋳塊とよばれる一種の鋳物を原材料とし、それに鍛造や圧延などの加工を加えて製作した鍛造品（打物）や圧延品、さらにそれらを溶接して製作した溶接品などがある。鋳物は鍛造品や圧延品に比べて結晶組織が粗く、成分の偏析（凝固の偏り）や巣（空隙(くうげき)）を含むことがあり、材質がもろい。しかし鋳物は複雑形状の品物の大量生産がしやすいので、自動車などの耐久消費材その他の機械部品として広く利用されている。

［井川克也・原善四郎］

鋳物の起源

鋳物の起源は新石器時代後期に土器焼成用の窯炉で金や銅が溶ける1000℃以上の温度が実現できるようになったときにさかのぼる。最古の鋳物はメコン川上流地方で発見された紀元前4500年の青銅斧(ふ)であろう。中近東では前4000～前3500年に銅斧が石製の開放型で鋳造されるようになり、前3000～前2500年に青銅が製錬されるようになって、柄穴付き青銅工具を中子(なかご)付き合せ型で鋳造する技術がヨーロッパへも広がっていった。中国では黄河中流地方に前1700年前後に青銅文化が生まれ、殷(いん)代には焼成粘土片を組み合わせた鋳型で複雑な文様と美麗な鋳肌をもった多様な形態の祭器を鋳造する技術をもつに至った。青銅に次いで製鉄技術が近東で前1500～前1000年に生まれ、中国でも前400年ころから鉄の製錬が始まったが、時を置かず鋳鉄の技術も現れ、前100年までには鋳鉄製農具が多量に生産されるようになった（ただし、ヨーロッパでは鋳鉄の生産は14世紀からである）。

　日本へは前300年ころから青銅器と鉄器が大陸からもたらされ、前100年ころから中子付き石製合せ型で渡来青銅原料による銅剣や銅鐸(どうたく)の鋳造が始まった。日本の製鉄は400年ころから始まっているが、鋳鉄鋳造の開始は仏教渡来に伴う鋳造技術の再渡来（6世紀）以後である。

［井川克也・原善四郎］

日本の鋳物業の発達

仏教とともに大陸から渡来した新鋳造技術は、鋳型材料として真土(まね)とよばれる粘土、砂の混合物を用いる、(1)組合せ鋳型法、(2)蝋(ろう)型法、(3)引型造型法などであった。7世紀から8世紀にかけて飛鳥(あすか)大仏や奈良大仏が(1)で、法隆寺阿弥陀(あみだ)三尊や新薬師寺諸仏が(2)で、諸寺の五重塔九輪や梵鐘(ぼんしょう)が(3)で製作された。奈良大仏は世界最大の鋳造品である。律令(りつりょう)制の下ではこれらの鋳造技術は近畿地方の諸官営工房で伝承されたが、平安時代にはそのほかに国衙(こくが)および荘園(しょうえん)所属の工房にも広がり、青銅製の梵鐘、仏具、鏡、鋳鉄製の灯籠(とうろう)、鍋(なべ)、釜(かま)が各地で製作されるようになった。平安末期にはそれらの工房が直営をやめ、工匠家族が年貢上納を条件に自営するようになった。たとえば河内(かわち)国丹南（大阪府堺(さかい)市美原区）の鋳物師集団は蔵人所(くろうどどころ)の灯籠供御人(くごにん)として鍋、釜の生産とその全国販売を許された。鎌倉大仏の鋳造に参加した丹南鋳物師が東国に土着することによって鋳造技術はさらに広がり、室町時代には各地に金屋(かなや)とよばれる鋳物師集落が成立し、江戸時代には江戸、京都のほかに佐野、山形、水沢、川口、桑名、高岡などが鋳物産地として栄えた。これらは明治時代における工業近代化の基盤をなした。

　江戸末期に幕府や諸藩は大砲鋳造、軍艦建造に力を入れ、釜石(かまいし)、鹿児島で洋式高炉が稼動、佐賀、韮山(にらやま)で反射炉により鋳鉄砲が鋳造された。これらはオランダ技術書からの知識と国内技術によるものであった。幕府がオランダ、フランスの技術援助で開設した長崎造船所、横須賀造船所のそれぞれから、機械鋳物用の乾燥型造型法および生砂(なまずな)型造型法が国内に普及した。

　明治政府もこれを引き継ぎ、海軍の横須賀、呉(くれ)、佐世保(させぼ)、舞鶴(まいづる)の各工廠(こうしょう)で優れた鋳造技術が育ち、後年民間の業界を先導することになった。また明治に入って民間の造船所もその数を増し、船舶建造のほかに陸用ボイラー、陸用蒸気原動機、鉱山機械、橋梁(きょうりょう)などにも進出し、鋳造製品の種類も多様化した。さらに都市の近代化に必要な上下水道の管を鋳鉄でつくるため大規模な民間工場も生まれた。

　明治中期から昭和10年代までは国力の伸長とともに鋳造工業も大いに発展した。このときに幕末期から明治にかけて生まれた大企業と、旧来の鋳物産地の二重構造が、後者は前者の下請け的性格をもつようになり、互いに支え合って鋳造工業の発展に寄与した。またこの時期は冶金(やきん)工学、機械工学、化学工学など鋳造技術の基礎となる学問が発達し、鋳物用金属材料、鋳型材料および造型法、鋳型の設計など学問的に基礎づけられて鋳造技術は一段と発展した。

［井川克也・原善四郎］

鋳物の種類と進歩

鋳物を材質別に分けると、鋳鉄鋳物、鋼鋳物、銅合金鋳物、軽合金鋳物となる。

［井川克也・原善四郎］

鋳鉄鋳物

鋳鉄鋳物は、溶解炉としてキュポラが普及し、燃料としてコークスが使われ、送風には電力による送風機が使われるようになって、溶解量、溶解速度、溶解温度が著しく向上した。鋳鉄の材質も炭素、ケイ素、マンガンの各量の調整によって種々変化することがわかり、銑鉄(せんてつ)や鋼屑(くず)の配合によってパーライト地に均一に片状黒鉛の分布したいわゆる菊目組織の鋳鉄鋳物が得られ、この材料が耐摩耗性に富み、引張り強さも大きく、機械部品に適していることが明らかにされた。また反射炉を使って鋳鉄を溶解し、成分をよく調整して、内面に金型を当てた鋳型に鋳込んで鋳物表面を硬くするチルド鋳物によるロールの製造に成功し、このロールは鋼の圧延に広く用いられた。さらに可鍛鋳鉄鋳物の製造に成功したのも明治末期で、白鋳鉄鋳物を焼鈍することにより、きわめて延性に富んだ鋳鉄が得られ、鉄管用継手として水道普及による膨大な需要にこたえることができた。

［井川克也・原善四郎］

鋼鋳物

鋼鋳物は、溶解温度が高く、凝固収縮も大きいので引け巣やピンホールなどの空隙(くうげき)が生じやすく、鋳造に高度の技術が必要である。明治年間はおもに平炉がその溶解に用いられ、溶解時間が長く温度も不十分であったので、なかなか良品を得ることはむずかしかった。大正年間に入って、初めてエルー式電弧炉が導入され、良質の鋳鋼品がつくられるようになった。

［井川克也・原善四郎］

銅合金鋳物

銅合金鋳物は、るつぼ炉で溶解され、銅88％、スズ10％、亜鉛2％の青銅がもっとも多く用いられ、砲金ともよばれている。銅合金は耐食性、耐海水性、靭(じん)性に富んでいるので、艦船方面に広く用いられる。その意味で海軍では活発な研究を行い、艦船の推進機の材料として1905年（明治38）ごろから青銅にかわって亜鉛40％、マンガン5％、アルミニウム1％以下のマンガン黄銅が用いられ、さらに昭和年代に入って亜鉛10または15％、ケイ素4％のシルジン青銅が使われるようになった。

［井川克也・原善四郎］

軽合金鋳物

軽合金鋳物は、アルミニウム系、マグネシウム系いずれも昭和年代に入ってから製造されるようになった。鋳造用アルミニウム合金としてはニッケルを含むY合金、ケイ素を含むシルミン、銅を含むラウタル、マグネシウムを含み耐食性のあるヒドロナリウムなどが航空機工業の発展に伴ってそれぞれの特徴に応じて用いられた。

　一方、マグネシウム合金は、アルミニウム、アルミニウムと亜鉛、マンガンなどとの合金が用いられたが、溶解時に酸化されやすく、鋳型にも酸化防止のくふうが必要で、マグネシウム合金鋳物の普及は容易には進まなかった。

　また昭和10年代にはアルミニウム合金のダイカスト（金型に溶融合金を圧入して凝固させる方法）も活況を呈するようになった。

　このように明治中期から昭和10年代にかけて発展したわが国の工業、ひいては鋳物工業も、第二次世界大戦が終わり敗戦を迎えてしばらくはまったくその生産が止まった。しかしその後の経済成長は目覚ましく、1950年（昭和25）の鋳物生産量が100万トン弱であったものが、73年には800万トンとなり、80年でも700万トンを上回っていた。

　その後は、ほぼ横ばいに推移し、2006年（平成18）の生産量は688万トンとなっている。

［井川克也・原善四郎］

製造技術の革新

鋳鉄鋳物については球状黒鉛鋳鉄の発明がある。これによって、もろいという鋳鉄の弱点が払拭(ふっしょく)され、強度部材にも用いられるようになった。自動車のクランクシャフトや高荷重に耐える鋳鉄管などに多用されている。また鋳鉄の溶解に低周波誘導電気炉が用いられるようになり、鋼屑に加炭して鋳鉄溶湯を得ることができ、成分や温度の制御、溶湯保持などが容易に行えるようになった。

　鋼鋳物の分野では鋳造方案や押湯の設計などに電子計算機を利用して健全な鋳物をつくるための理論的解明が進められている。

　銅合金の分野では、船舶の推進機材料として10％アルミニウムを含むアルミニウム青銅が伸びている。

　軽合金鋳物ではとくにアルミニウムダイカストの伸びが著しい。10％ケイ素を含むシルミン合金が用いられる。また高純度亜鉛地金が精錬技術の向上によって容易に入手できるようになったので、従来、鉛、カドミウムなどの不純物のため、もろくて使用できなかった亜鉛ダイカストが、今日では広く用いられるようになっている。

　鋳物の工場生産能率は鋳型製造技術によって支配されるといっても過言ではない。第二次世界大戦までの鋳型といえば、珪砂(けいさ)に粘土と水を混ぜて粘結したものに限られていたが、その後今日まで枚挙にいとまがないほど新しい造型法が次々と誕生した。フェノール樹脂を粘結剤とするシェルモールド法は、粘結剤として用いられる有機物が、鋳込み後、熱分解して粘結力を失うので、鋳物砂の再生がきわめて容易である。次に、水ガラスを粘結剤とし炭酸ガスを吹き込んで反応させ短時間に硬化させる炭酸ガス型法は、鋳型強度が大きく、乾燥型にかわるものとして普及した。また塩化ビニル膜を利用して砂型内を真空にし、外圧によって鋳型を固めるVプロセス法は、粘結剤をまったく使わない方法で、日本で発明され、世界的に注目を集めている造型法である。

　しかし、粘土と水分によって鋳物砂を粘結する在来の生砂型法は、造型が簡単で、経費も低廉ですむので、生砂型用の造型機が高速化、高圧化、大型化することによって現在でも造型法の主流を占めている。

　精密鋳物の製作法として、現在ふたたび奈良時代からあった蝋(ろう)型法が復活している。ロストワックス法とよばれるもので、精密な金型によってワックス製の模型をつくり、これを耐火物粉末とエチルシリケート溶液の混合泥状物に埋め、乾燥、焼成してワックスを溶かし出し、鋳型とする方法である。この方法は、タービンブレードのように複雑曲面をもっていて、ほかの加工法ではその曲面をつくりだすことがむずかしい部品や、塑性加工や切削加工ができない特殊合金型部品の製作などに応用されている。

［井川克也・原善四郎］

[参照項目] | 鋳物師 | 球状黒鉛鋳鉄 | 鋳造

築地反射炉

韮山反射炉
江戸時代末期、伊豆代官江川英龍が大砲鋳造のため韮山に建設した反射炉。耐火れんがをアーチ形に組んだ天井に炉の熱を反射させて鉄を溶かした。煙突の高さは16m。ほぼ完全な形で残る日本唯一の反射炉の遺構である。国指定史跡　世界文化遺産「明治日本の産業革命遺産　製鉄・製鋼、造船、石炭産業」の一部（2015年登録）　静岡県伊豆の国市©静岡県観光協会">

韮山反射炉

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例

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