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Features
The valve stem is not 美姐only a moving part, a 舊歌force-receiving part, but al很哥so a sealing part during the opening an道器d closing process of the valv明美e. At the same time, it 市鐘is impacted and corroded by the med物劇ium, and it also generates fri畫場ction with the filler. Therefore, when亮紅 selecting the valve視大 stem material, it must b和討e ensured that it has 高媽sufficient strength, goo說雨d impact toughness, scratch res美人istance, and corrosion resistan銀農ce at the specified tem上道perature. The valve stem好音 is a vulnerable part, and atte月物ntion should be paid to the machi快放ning performance and heat treatmen線站t performance of the 什什material when selecting it.
Commonly used materials
1. Copper alloy
Generally, the selecte生畫d grades are QA19-2, HPb59-1-1. It is s制志uitable for low pressure valves with n下黃ominal pressure less tha兵了n or equal to 1.6MPa and temp和行erature less than or equal to 200 de飛來grees.
2. Carbon steel
Generally, A5 and 35 steel are se長去lected, after nitriding紅民 treatment, they are s資那uitable for ammonia val制見ves with a nominal pressure 算著less than or equal t謝習o 2.5MPa, and low and medium press月姐ure valves for water, steam and other美你 media. A5 steel is suitable for物鄉 valves whose temperature doe刀務s not exceed 300 degrees; 35 st購有eel is suitable for 那章valves whose temperature does not excee們微d 450 degrees. (Note: The actu船答al route proves that the valve ste路新m made of carbon steel ni雪新triding can not solve the corrosi煙金on resistance problem well and 道會should be avoided.)
3. Alloy steel
Generally choose 40Cr, 38CrMoA場路1A, 20CrMo1V1A and other mate討舊rials. After 40Cr is c為老hrome-plated, it is suita亮人ble for water, steam, petroleum and 吧長other media with a nominal pressu草些re of 32MPa or less and喝一 a temperature of 450 degrees or less. 聽書38CrMoA1A has undergo資個ne nitriding treatment and can wit了兵hstand a pressure of 10MPa at a worki日報ng temperature of 540 degrees. It 慢做is often used in power station valves. 公習After nitriding treatment個能, 20CrMo1V1A can withstand a pressure o村河f 14MPa at a working temperature of時黃 570 degrees, and is 白就often used in power station valves綠鐵.
4. Generally, 2Cr13, 3Cr13, 1Cr件相17Ni2, 1Cr18Ni12Mo2Ti and ot土懂her materials are used. 2Cr間開13, 3Cr13 stainless steel i厭器s suitable for water, 女照steam and weakly corrosive media 謝不with nominal pressure less than or eq不見ual to 32MPa and tem師快perature less than or equa件雜l to 450 degrees. The surface can快數 be strengthened by met店機hods such as chrome 報術plating and high frequency quenchin視場g. The 1Cr17Ni2 stainless st森服eel valve and low temperat嗎了ure valve are resistant to我我 corrosive media. 1C跳拍r18Ni9Ti, 1Cr18Ni12Mo2Ti stainless計睡, acid-resistant steel is used in high 妹體temperature valves with a nomin有空al pressure of 6.4MPa or less and a黑章 temperature of 600 degre小鐵es or less, and can also be used i章呢n stainless steel valves and low t窗多emperature valves wi區麗th a temperature of -100 degrees or l會兒ess. 1Cr18Ni9Ti is r做去esistant to corrosive media such as 開算nitric acid; 1Cr18Ni12Mo2Ti is resist頻新ant to corrosive media such長拍 as acetic acid. Whe雪我n 1Cr18Ni9Ti and 1Cr18Ni12件見Mo2Ti are used in high-temperature制樹 valves, nitriding treatm理信ent can be used to improve scratch 她時resistance.
5. Bearing chrome steel
Select GCr15, which is su國用itable for ultra-high pressure valve你離s with nominal pressur笑吃e less than or equal t還人o 300MPa and temperature less than 友少or equal to 300 degr資技ees.
There are many materials used t間國o make valve stems, including 4Cr10Si業匠2Mo martensitic heat-resistan很錢t steel, 4Cr14Ni14W2Mo a章睡ustenitic heat-resistant steel and so 為化on.
The stem nut and the stem are ma廠看tched with threads to directly 樂也bear the axial force o很亮f the stem, and the friction between th開裡e plate and the bracket些行 and other valve parts. Therefore,看快 in addition to a ce這木rtain strength, the valve stem nut al筆學so requires the properties of low frict都見ion coefficient, no corrosion, and no s店工eizure with the valve stem.
