焊縫RT底片的評判規(guī)律及典型缺陷圖譜

1、焊縫射線照相底片的評判規(guī)律一、 探傷人員要評片，四項指標(biāo)放在先*，底片標(biāo)記齊又正，鉛字壓縫為廢片。 二、 評片開始第一件，先找四條熔合線，小口徑管照橢圓，根部都在圈里面。 三、 氣孔形象最明顯，中心濃黑邊緣淺，夾渣屬于非金屬，雜亂無章有棱邊。 四、 咬邊成線亦成點，似斷似續(xù)常相見，這個缺陷最好定，位置就在熔合線。 五、 未焊透是大缺陷，典型圖象成直線，間隙太小鈍邊厚，投影部位靠中間。 六、 內(nèi)凹只在仰焊面，間隙太大是關(guān)鍵，內(nèi)凹未透要分清，內(nèi)凹透度成弧線。 七、 未熔合它斜又扁，常規(guī)透照難發(fā)現(xiàn)，它的位置有規(guī)律，都在坡口與層間。 八、 橫裂縱裂都危險，橫裂多數(shù)在表面，縱裂分布范圍廣，中間稍寬兩端尖

2、。 九、 還有一種冷裂紋，熱影響區(qū)常發(fā)現(xiàn)，冷裂具有延遲性，焊完兩天再拍片。 十、 有了裂紋很危險，斬草除根保安全，裂紋不論長和短，全部都是級片。 十一、 未熔和也很危險，黑度有深亦有淺，一旦判定就是它，亦是全部級片。 十二、 危害缺陷未焊透，級焊縫不能有，管線根據(jù)深和長，容器跟著條渣走*。 十三、 夾渣評定莫著忙，分清圓形和條狀，長寬相比3為界，大于3倍是條狀。 十四、 氣孔危害并不大，標(biāo)準(zhǔn)對它很寬大，長徑折點套厚度，中間厚度插入法。 十五、 多種缺陷大會合，分門別類先評級，2類相加減去，3類相加減級。 十六、 評片要想快又準(zhǔn)，下拜焊工當(dāng)先生，要問訣竅有哪些，焊接工藝和投影。 注：*四項指標(biāo)系

3、底片的黑度、靈敏度、清晰度、灰霧度必須符合標(biāo)準(zhǔn)的要求。     *指單面焊的管線焊縫和雙面焊的容器焊縫內(nèi)未焊透的判定標(biāo)準(zhǔn)。Radiograph Interpretation - WeldsIn addition to producing high quality radiographs, the radiographer must also be skilled in radiographic interpretation. Interpretation of radiographs takes place in three basic steps wh

4、ich are (1) detection, (2) interpretation, and (3) evaluation. All of these steps make use of the radiographer's visual acuity. Visual acuity is the ability to resolve a spatial pattern in an image. The ability of an individual to detect discontinuities in radiography is also affected by the lig

5、hting condition in the place of viewing, and the experience level for recognizing various features in the image. The following material was developed to help students develop an understanding of the types of defects found in weldments and how they appear in a radiograph.DiscontinuitiesDiscontinuitie

6、s are interruptions in the typical structure of a material. These interruptions may occur in the base metal, weld material or "heat affected" zones. Discontinuities, which do not meet the requirements of the codes or specification used to invoke and control an inspection, are referred to a

7、s defects.General Welding DiscontinuitiesThe following discontinuities are typical of all types of welding.Cold lap is a condition where the weld filler metal does not properly fuse with the base metal or the previous weld pass material (interpass cold lap). The arc does not melt the base metal suff

8、iciently and causes the slightly molten puddle to flow into base material without bonding. Porosity氣孔 is the result of gas entrapment in the solidifying metal. Porosity can take many shapes on a radiograph but often appears as dark round or irregular spots or specks appearing singularly, in clusters

9、 or rows. Sometimes porosity is elongated and may have the appearance of having a tail This is the result of gas attempting to escape while the metal is still in a liquid state and is called wormhole porosity. All porosity is a void in the material it will have a radiographic density more than the s

10、urrounding area.Cluster porosity 鏈狀氣孔is caused when flux coated electrodes are contaminated with moisture. The moisture turns into gases when heated and becomes trapped in the weld during the welding process. Cluster porosity appear just like regular porosity in the radiograph but the indications wi

11、ll be grouped close together.Slag inclusions夾渣 are nonmetallic solid material entrapped in weld metal or between weld and base metal. In a radiograph, dark, jagged asymmetrical shapes within the weld or along the weld joint areas are indicative of slag inclusions.Incomplete penetration (IP) or lack

12、of penetration (LOP) 未焊透occurs when the weld metal fails to penetrate the joint. It is one of the most objectionable weld discontinuities. Lack of penetration allows a natural stress riser from which a crack may propagate. The appearance on a radiograph is a dark area with well-defined, straight edg

13、es that follows the land or root face down the center of the weldment. Incomplete fusion 未熔合is a condition where the weld filler metal does not properly fuse with the base metal. Appearance on radiograph: usually appears as a dark line or lines oriented in the direction of the weld seam along the we

14、ld preparation or joining area.Internal concavity or suck back 內(nèi)凹或吸入is condition where the weld metal has contracted as it cools and has been drawn up into the root of the weld. On a radiograph it looks similar to lack of penetration but the line has irregular edges and it is often quite wide in the

15、 center of the weld image.Internal or root undercut 內(nèi)部或根部咬邊is an erosion of the base metal next to the root of the weld. In the radiographic image it appears as a dark irregular line offset from the centerline of the weldment. Undercutting is not as straight edged as LOP because it does not follow a

16、 ground edge.External or crown undercut 外部或頂部咬邊is an erosion of the base metal next to the crown of the weld. In the radiograph, it appears as a dark irregular line along the outside edge of the weld area. Offset or mismatch 錯邊are terms associated with a condition where two pieces being welded toget

17、her are not properly aligned. The radiographic image is a noticeable difference in density between the two pieces. The difference in density is caused by the difference in material thickness. The dark, straight line is caused by failure of the weld metal to fuse with the land area.Inadequate weld re

18、inforcement 未填滿is an area of a weld where the thickness of weld metal deposited is less than the thickness of the base material. It is very easy to determine by radiograph if the weld has inadequate reinforcement, because the image density in the area of suspected inadequacy will be more (darker) th

19、an the image density of the surrounding base material.Excess weld reinforcement 增強(qiáng)余高is an area of a weld, which has weld metal added in excess of that specified by engineering drawings and codes. The appearance on a radiograph is a localized, lighter area in the weld. A visual inspection will easily

20、 determine if the weld reinforcement is in excess of that specified by the individual code involved in the inspection.Cracking 裂紋can be detected in a radiograph only the crack is propagating in a direction that produced a change in thickness that is parallel to the x-ray beam. Cracks will appearas j

21、agged and often very faint irregular lines. Cracks can sometimes appearing as "tails" on inclusions or porosity. Discontinuities in TIG weldsThe following discontinuities are peculiar to the TIG welding process. These discontinuities occur in most metals welded by the process includin

22、g aluminum and stainless steels. The TIG method of welding produces a clean homogeneous weld which when radiographed is easily interpreted.Tungsten inclusions. 夾鎢Tungsten is a brittle and inherently dense material used in the electrode in tungsten inert gas welding. If improper welding procedures ar

23、e used, tungsten may be entrapped in the weld. Radiographically, tungsten is more dense than aluminum or steel; therefore, it shows as a lighter area with a distinct outline on the radiograph.Oxide inclusions 夾氧化物are usually visible on the surface of material being welded (especially aluminum). Oxid

24、e inclusions are less dense than the surrounding materials and, therefore, appear as dark irregularly shaped discontinuities in the radiograph.Discontinuities in Gas Metal Arc Welds (GMAW)The following discontinuities are most commonly found in GMAW welds.Whiskers are short lengths of weld electrode wire, visible on the top or bottom surface of the weld or contained within the weld. On a radiograph they appear as light, "wire like" indications.Burn through (icicles) results when too much heat causes ex