特钢圈都需了解的PREN耐点蚀当量,究竟是个什么
发布时间:2018-08-26 20:44这几天在后台,不断有读者问PREN的问题。今天周末,抽空和大家分享下。
点蚀当量值又称为耐点蚀当量,英文为Pitting Resistance Equivalent Number,简称PREN,是一种以金属中某些元素的质量分数为基础计算的一套算法,数值常被用于耐点腐蚀比较的评定方法。
在不同版本的资料中,存在着几个PREN的公式,但一般来说,这个公式是用量最广的:PREN =Cr %+ 3.3 *Mo% + 16 *N%。
“特钢100秒”查阅资料,查阅有一个版本的耐点蚀当量值PREN公式更为准确:PREN=Cr%+3.3 *(Mo+0.5W)%+16 *N%,因一般较少几种合金含有W,故流传和广为使用的还是把W去掉的这个公式^_^
具有较高的PREN值的金属表现出比PREN值低的金属更耐局部腐蚀。用这个公式计算出来的值,基本表现了相对耐点腐蚀程度。
一般来说,PREN值大于32的金属可用于耐海水点腐蚀。为安全和稳定起见,PREN值大于40的材料如S31254超级不锈钢和S32750超级双相钢常用于海洋环境。
抗点蚀测量方法:
在ASTM G48标准中,详细规定了精确的点蚀试验流程。
常见特种金属的耐点腐蚀当量PREN值如下:
以上部分有钢厂的注册商标,权益归对应公司所有。
来,先让小编搬出原文,英文好的读者可以自己仔细阅读下:
Pitting resistance equivalent number (PREN) is a predictivemeasurement of a stainless steel's resistance to localized pitting corrosionbased on its chemical composition. In general: the higher PREN-value, the moreresistant is the stainless steel to localized pitting corrosion by chloride.
PREN is frequently specified when stainless steels will be exposedto seawater or other high chloride solutions. In some instances stainlesssteels with PREN-values > 32 may provide useful resistance to pitting corrosionin seawater, but is dependent on optimal conditions. However, crevice corrosionis also a significant possibility and a PREN > 40 is typically specified forseawater service.
PREN Formulas (w/w)
There are several PREN formulas. The most common is PREN = 1 x %Cr+ 3.3 x %Mo + 16 x %N
There are a few stainless steels which add tungsten (W), for thosethe following formula is used PREN = 1 x %Cr + 3.3 ( %Mo + 0.5 x %W ) + 16 x %N
Pitting Resistance Measurement
Exact pitting test procedures are specified in the ASTM G48standard.