Piano wire - Pianosen

This is a high-grade carbon steel wire made for applications that require the highest spring performance, such as pianos. JIS specifies several types of piano wire with a range of C 0.65-0.95 mass%, Si 0.12-0.32 mass%, and Mn 0.30-0.90 mass%, and high quality is required, especially with low levels of impurities such as P, S, and Cu, and with very few surface defects such as scratches and decarburization. This piano wire is used as the raw material, and is austenitized at 900 °C or higher, then quenched in molten lead at around 500 °C, transformed into a fine pearlite structure (this is called patenting treatment), air-cooled, and wiredrawn at room temperature. This heat treatment and processing are repeated several times to finish the wire to the desired thickness, and finally, wiredrawing is performed with a cross-sectional area reduction rate of 90% or more to finish the piano wire to a diameter of 0.1 mm or less, resulting in a tensile strength of 350 kg mm ^-2 or more. After drawing, it is annealed at a low temperature of around 300°C to sufficiently increase the elastic limit and yield point before use. When used as a spring, low-temperature annealing after winding it into a coil also helps to stabilize the spring shape. [See other terms] Spring steel

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

ピアノをはじめとして最高度のばね性能が要求される用途のためにつくられた高級炭素鋼線．JISのピアノ線材はC 0.65～0.95質量％，Si 0.12～0.32質量％，Mn 0.30～0.90質量％ の範囲で数種類が規定され，とくにP，S，Cuなどの不純物が少なく，きず，脱炭などの表面欠陥も非常に少ないなど高度の品質が要求されている．このピアノ線材を素材として，900 ℃ 以上でオーステナイト化した後500 ℃ 付近の溶融鉛中に急冷し，微細パーライト組織に変態させて(これをパテンティング処理という)空冷し，常温で線引き加工をほどこす．このような熱処理と加工を交互に数回繰り返して目的の太さに仕上げるが，最後に断面減少率で90％ 以上の線引き加工をほどこして直径0.1 mm 以下に仕上げたピアノ線の引張強さは350 kg mm^－2 以上にも達する．線引き後300 ℃ 付近で低温焼なましして弾性限界，降伏点を十分に上げて使用する．ばねとして用いる場合は，コイル状に巻いてから低温焼なましを行うと，ばね形状の安定化にも役立つ．[別用語参照]ばね鋼

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