不锈钢焊缝铁素体含量测试方法与精度的现状及进展

Progress in Methods and Precision of Ferrite Content Determination for Stainless Steel Weld

铁素体含量对不锈钢焊缝的耐蚀、韧性、强度等性能有重要影响,准确测量或预测十分重要.铁素体含量的测试与预测方法有很多种,最常使用的是图谱法和磁测法,介绍这两种方法的最新进展.在不同实验室制备及测量试样、试样表面是否进行处理等都会影响测试与预测结果的精度.铁素体数（Ferrite number,FN）小于5时,不同实验室之间图谱法预测结果的波动是平均值的±60％,铁素体数在15～35时,图谱法预测结果的波动是平均值的±30％.磁测法测量的波动是平均值的±20％,小于图谱预测法,是目前较精确的测试方法.新的预测方法考虑了元素之间相互作用和冷却速度等因素对铁素体含量的影响,提高了预测的精度.针对铁素体数测试结果不可避免的波动问题,提出目标范围这一概念来解决焊材设计者与使用者对测试结果产生的分歧.

Ferrite content is very important as its content will influence the corrosion resistance,toughness,strength and other property of stainless steel weld.There are a lot of methods can determinate ferrite content,the diagram and the magnetic ferrite content testing methods are usually used.The latest progress of these two methods is reviewed.Samples preparation and measurement among several laboratories,surface process and so on all influence the precision of ferrite content determination.When ferrite content is less than 5 ferrite number（FN）,the variation of prediction according to the diagram testing methods is ±60％ of average value.However,the experience data shows that the variation is about ±30％ of average value,when FN is at FN values of 15 to 35.As a relative more precise measured method,magnetic method has successfully reduced the variation to ±20％ of average value,which is less than that of diagram method.The new prediction methods,considering the effect of element interactions,cooling rate on the ferrite content,promoted its predicted accuracy.＂target scope＂ of FN is suggested to deal with the controversy between welding material designer and user on test result due to the inevitable variation in ferrite content testing.