原文：
锻钢低温截止阀适用于低温液体贮运设备的管理系统，具有开关灵活、密封可靠的特点，也可用于其他低温和深冷介质的管理系统.。常温截止阀是指介质的使用温度-40~+500度之间，阀体的材料也不一样。低温截止阀主要是指介质使用温度在-196~-150度的低温液态介质系统中的截止阀。 低温阀门，特别是超低温阀门，其工作温度极低。在设计这类阀门时，除了应遵循一般阀门的设计原则外，还有一些特殊的要求。 一、低温阀门的设计要求:根据使用条件，低温阀的设计有下列要求：1) 阀门在低温介质及周围环境温度下应具有长时间工作的能力。2) 阀门不应成为低温系统的一个显著热源。这是因为热量的流入除降低热效率外，如流入过多，还会使内部流体急速蒸发，产生异常升压，造成危险。3) 低温介质不应对手轮操作及填料密封性能产生有害的影响。4) 直接与低温介质接触的阀门组合件应具有防爆和防火结构。5) 在低温下工作的阀门组合件无法润滑，所以需要采取结构措施，以防止摩擦件擦伤。 二、低温阀的材料选用 1、低温阀主体材料 (1) 主体材料选用应考虑的因素 从金相考虑，金属材料中除了具有面心立方晶格的奥氏体钢、铜、铝等以外，一般的钢材在低温状态下会出现低温脆性，从而降低阀门的强度和使用寿命。选择主体材料时首先要选用适合于低温下工作的材料。铝在低温下不会出现低温脆性，但因铝及铝合金的硬度不高，铝密封面的耐磨、耐擦伤性能差，所以在低温阀门中的使用有一定的限制，仅在低压和小口径阀门中选用。 在低温工作的材料要保证其低温性能，主要是保证其冷冲击强度。阀内件必须通过正确选材，使其具有足够的冷冲击强度，才能防止断裂。C和Cr的合金钢在低于－20℃时候很快失去抗冲击强度，所以使用温度分别限制在-30℃和-50℃。含Ni量为3.5%的镍钢可以使用到-100℃，含Ni量9%的镍钢可以使用到-192℃。奥氏体不锈钢、镍、蒙乃尔合金、哈氏合金、钛、铝合金及青铜可以使用到更低的温度(-273℃)。 除此以外，低温阀门的材料选用还应考虑以下一些因素： 1) 阀门的{zd1}使用温度；2) 金属材料在低温下保持工作条件所需要的力学性能，特别是冲击韧性、相对延伸率及组织稳定性； 3) 在低温及无油润滑的情况下，具有良好的耐摩性；4) 具有良好的耐蚀性；5) 采用焊接连接时还需考虑材料的焊接性能。 (2) 阀体、阀盖、阀座、阀瓣（闸板）材料的选用，这些主体零部件材料的选用原则大致是：温度高于-100℃时选用铁素体钢；温度低于-100℃时选用奥氏体钢；低压及小口径阀门可选用铜和铝等材料。设计时根据{zd1}使用温度选择适当的材料。 (3) 阀杆及紧固件的材料选用 温度高于-100℃时，阀杆和螺栓材料采用Ni、,Cr-Mo等合金钢，经适当的热处理，以提高抗拉强度和防止螺纹咬伤等。温度低于-100℃时， 采用奥氏体不锈耐酸钢制造。但18-8耐酸钢硬度低，会造成阀杆与填料相互擦伤，致使填料处泄漏。所以，阀杆表面必须镀硬铬（ 镀层厚0.04-0.06mm），或进行氮化和镀镍磷处理，以提高表面硬度。为防止螺母与螺栓咬死，螺母一般采用Mo钢或Ni钢，同时在螺纹表面涂二硫化钼。 2、低温阀垫片、填料材料的选用:随着温度降低，氟塑料收缩量很大，会使密封性能下降，容易引起泄漏。石棉填料无法避免渗透性泄漏。橡胶对液化天然气有泡胀性，在低温下不可采用。在低温阀门设计中，一方面由结构设计来保证使填料处于接近环境温度下工作，例如，采用长颈阀盖结构，使填料函离。

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译文：
Forged steel cryogenic valves for cryogenic storage and transportation equipment management system with switch flexible, reliable sealing characteristics can also be used for other low-temperature and cryogenic media management system.. Temperature cut-off valve is the medium temperature -40 ~ +500 degrees, not the same body of material. Low-temperature valve mainly refers to the medium temperature in the -196 ~ -150 degree temperature liquid medium system valve. Low-temperature valves, cryogenic valves in particular, its low operating temperature. In the design of such valves, in addition to the design of the valve should follow the general principle, there are some special requirements. First, low temperature valve design requirements: According to the terms of use, low-temperature valve design has the following requirements: 1) the valve in the cold medium and the surrounding ambient temperature should have the ability to work long hours. 2) The valve should not be a low temperature system, a significant heat source. This is because the heat flow in addition to lowering thermal efficiency, such as excessive inflows, but also to the internal fluid rapid evaporation, resulting in abnormal pressure, dangerous. 3) low-temperature media should not be rival operating and packing sealing performance wheel harmful effects. 4) direct contact with the cold medium valve assembly should have the explosion-proof and fireproof structures. 5) to work at low temperature lubrication of the valve assembly can not, so they need to take structural measures to prevent the friction parts scratches. Second, the selection of materials at low temperature valve 1, low temperature valve of the main materials (1) of the main factors to be considered material selection Consideration of microstructure, the metal material in addition to face-centered cubic lattice with the austenitic steel, copper, aluminum outside, the general condition of steel at low temperatures occur at low temperature brittleness, which reduces the strength and service life of the valve. First choice of the main material used to work for low-temperature materials. Aluminum does not appear in the low temperature low temperature brittleness, but the hardness of aluminum and aluminum alloys is not high, aluminum sealing surface of the wear and abrasion resistance performance is poor, so the use of low-temperature valves have certain limitations, only low and small-caliber valve in use. Work in low-temperature materials to ensure the low temperature performance, mainly to ensure the cold impact strength. Trim must correct selection, it has enough cold impact strength, in order to prevent breakage. C and Cr alloy steel below -20 ℃ often quickly lose impact strength, so limit the use of temperatures -30 ℃ and -50 ℃. With Ni content of 3.5% nickel steel can be used to -100 ℃, with Ni content of 9% nickel steel can be used to -192 ℃. Austenitic stainless steel, nickel, Monel, Hastelloy, titanium, aluminum and bronze can be used to lower temperature (-273 ℃). In addition, low temperature valve material selection should also consider the following factors: 1) The minimum temperature valve; 2) Metal working conditions at low temperature to maintain the required mechanical properties, especially impact toughness, elongation and organization of the relative stability; 3) and oil-free lubrication at low temperature case, good abrasion resistance; 4) has a good corrosion resistance; 5) the use of welded connections need to consider the material welding. (2) Body, bonnet, seat, valves, valve (gate) material selection, material selection of these main components are generally the principle: when the temperature is higher than -100 ℃ selected ferritic steel; temperature below - 100 ℃, the selection of austenitic steel; low pressure and small-caliber valve can be used such as copper and aluminum materials. Design under the minimum temperature select the appropriate materials. (3) stem and material selection of fasteners Temperature is higher than -100 ℃, the stem and bolt material is Ni,, Cr-Mo alloy steel, etc., by appropriate heat treatment to improve the tensile strength and prevent the screw bites. Temperature lower than -100 ℃, the use of austenitic stainless acid-resistant steel. However, the low hardness of 18-8 acid-resistant steel will cause the stem and packing scratches each other, resulting in leakage of padding. Therefore, the stem surface to be hard chrome plated (plating thickness 0.04-0.06mm), or nitrogen and phosphorus nickel plating to enhance the surface hardness. Killed to prevent the nuts and bolts, nuts generally used steel or Ni Mo steel, while the threads coated with molybdenum disulfide. 2, low temperature valve gasket, packing materials used: as the temperature decreased, fluorine plastic shrinkage great sealing performance will fall easily lead to leaks. Asbestos packing can not prevent the permeability leak. There are foam rubber on the expansion of liquefied natural gas, can not be used at low temperatures. In the low-temperature valve design on the one hand by the structure design to ensure that the filler is close to the ambient temperature, for example, valve cover structure with long neck, so that stuffing away.