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1、无损检测方法概述NDT METHOD INTRODUCE,常规4大方法 Four general NDT methods1、超声波检测（UT）（内部缺陷） Ultrasonic Test (UT) (detecting internal defect)2、射线检测（RT） （内部缺陷） Radiographic Test (RT) (detecting internal defect)3、渗透检测（PT) （表面开口型缺陷） Penetration Test (PT) (detecting surface opening defect)4、磁粉检测（MT) (表面和近表面缺陷） Magneti
2、c Test (MT)(detecting surface and near surface defect),超声波探伤的基本原理 Theory of Ultrasonic Test,超声波探伤是利用超声能透入金属材料的深处，并由一界面进入另一界面时，在界面边缘发生反射的特点来检查零件缺陷的一种方法，当超声波束自零件表面由探头通至金属内部，遇到缺陷与零件底面时就分别发生反射波来，在荧光屏上形成脉冲波形，根据这些脉冲波形来判断缺陷位置和大小。When Ultrasonic wave energy enter the metal ,it will occur echo at the differe
3、nt medium surface(such as defect surface),and we observe the pulse echo from the UT equipment screen,UT方法特征Character of UT,UT主要检测内部缺陷：UT main inspection internal defect1.UT对薄板适用性差，尤其厚度小于8mm It is difficult to find thin thickness plate defect by UT,especialy the plate thickness is less than 8mm.2.对奥氏
4、体不锈钢适用性差，晶粒粗大,杂波多，衰减大 It is difficult to find the austenitic steel defect,because the austenitic steel crystal is crassitude,and it will appear big grass echo. At the same time the sound wave energy will rapidly reduce.3.UT检测时，放置探头的一面存在盲区，盲区范围根据探头角度、晶片尺寸、频率等确定 It will have dead zone near the probe p
5、utting surface.The dead zone size is different according to the probe angle,crystal size and frequency4.超声波检测能测出缺陷的长度和深度，但对缺陷定性比较困难 It can measure length and depth of defect by UT,but it is difficult to judge the nature of the indication.5.对粗糙、形状不规则、小、薄或非均质材料难以检查 It is difficult to inspect the un-re
6、gular, rough,small or thin production,磁粉探伤的基本原理 Theory of Magnetic Test,磁粉探伤是对铁磁性材料或零件经外加磁场磁化后，由于金属是连续均匀的，故磁力线的分布是均匀的。当零件表面或近表面有缺陷存在时磁力线的密度发出变化。磁力线突变，而磁力线暴露在空气中，形成漏磁场，利用带有导磁性材料的磁粉施加在零件磁化区表面，使漏磁场吸附磁粉，称为磁痕显示，用肉眼观察有无缺陷 The magnetic line is well-proportioned when we magnetize the non defect ferromagneti
7、sm material .The magnetic line will change when the surface or near surface has defect,and we can use magnetic particle to catch the change,it will has magnetic figure appearance.,MT方法特征Character of MT,MT主要检测表面缺陷及近表面缺陷main inspection surface and near surface defect1.此方法只适用于铁磁性材料It only can inspect t
8、he ferromagnetism material2.不能检测奥氏体不锈钢材料及奥氏体不锈钢焊条焊接的焊缝It can not inspect austenitic stainless steel material and welding3.对于表面小的划伤、埋藏较深的内部缺陷、与磁力线夹角小于30度的分层和折叠缺陷难以发现It can not detect below defect,such as; small nick on the surface,internal defect in deep, delamination which the angle less than 30 deg
9、ree with magnetic line4.此方法检测的深度根据磁粉探伤机的不同而不同，一般约13mm。类似镜板之类的产品，如果需要做探伤，可在精加工前约0.51mm时做磁粉探伤。It general can detect defect which below surface about 1mm to 3mm.Such as We suggest to do MT before final machine about 0.5mm to 1mm5.仅能显出缺陷的长度和形状，而难以确定其深度；对剩磁有要求的一些工件，经磁粉探伤后还需要退磁。It only can measure the len
10、gth and the figure of the defect,it is difficult to measure the defect depth.It need to demagnetization when the product have the remanence requirement.,渗透探伤的基本原理 Theory of Penetrant Test,渗透探伤的基本原理是利用毛细现象使渗透液渗入缺陷，经清洗使表面渗透液去除，而缺陷中的渗透液残留，再利用显像剂的毛细管作用吸附出缺陷中残留渗透液而达到检验缺陷的目的 It according as capillary phen
11、omenon ,when the penetrant come into the opening defect,we clean the surface penetrant,and spray debeloper to adsorb the penetrant from the defect,and it will appear figure.,PT方法特征Character of PT,PT主要检测表面开口型缺陷main inspection surface opening defect.1.此方法不适用于检测多孔性材料It can not insepct lacunaris materia
12、l2.PT对埋藏缺陷是检测不出来的It can not inspect non opening defect.3.如果不是最终的产品表面，PT探伤完成后，继续加工会把探伤合格的表面去除掉，后面露出的表面无法保证合格。It can not ensure the final machine surface quality if we do PT in the rough machine phase4.仅能显出缺陷的长度和形状，而难以确定其深度It only can detect the length and figure of the defect,it is difficult to measu
13、re the defect depth.,射线探伤的基本原理Theory of Radiographic Test,射线探伤法是利用射线对各种物质的穿透力，检验物质内部缺陷的一种方法，射线是一种能量很高，具有一定穿透能力的光量子。当与被检验物质相作用时，由于缺陷部位与无缺陷的部位的厚度和密度不同，因此对射线的衰减程度不同，透过有缺陷部位的射线强度不同。把被检验部位内部组织和结构情况变成射线强度差表现出来，利用胶片或其他仪器设备检测透过的射线强度，就可以检测出工件内部的质量情况。达到检验探伤目的 When the radial energy thrill through the metal,it
14、 will attenuate.The attenuation is different according to the different material,when the material has the defect,it will appear the film,we can observe the film to find the defect shadow,RT方法特征Character of RT,RT主要检测内部缺陷main inspection internal defect1.RT对大厚板适用性差，尤其100mm厚度以上，一般40mm厚度以上就选择射线探伤 It is
15、difficult to inspect the thick plate, especially the thickness is more than 100mm.We general choose the ray when the thickness is more than 40mm.2.RT由于缺陷是显示在底片上，因此可以相对准确的对缺陷定性，如夹渣、气孔、未熔合、裂纹 It is easy to judge the nature of the defect,such as;porosity,slag, lack of fusion , lack of penetration ,crack.3.缺点不能定位缺陷的埋藏深度 It can not measure the depth of the defect.4.对安全防护有要求 It should have safety protection,目前厂内常用探伤标准及探伤范围列表comparsion list for per standard,
