The Importance of X-ray Inspection for Weld


There is no doubt that continuous technological advancements have enhanced the quality of manufactured products. One of the advancements is the precise inspection of products using X-rays. 

X-ray inspection helps in increasing productivity with minimal or zero wastage.

Have you ever wondered why X-ray weld inspection is highly recommended for various manufacturers especially in the welding sector? No more wonders then! 

This article will highlight the significance of X-ray for the inspection of welds.

What is the importance of welding inspection?

The size of the weld and the occurrence of weld defects – Usually, these are the major attributes to be assessed during weld inspection. 

Weld size – It’s the weld size that is directly related to its strength and performance. Suppose if the size of the weld is very less, it cannot withstand stress during service.

Weld defects – Defects or imperfections may arise depending on the size or location of the welds. 

There are various types of welds defects such as

  • Porosity
  • Slag inclusion
  • Lack of fusion
  • Toe crack
  • Incomplete penetration
  • Internal or external undercut
  • Cold lap
  • Internal concavity
  • Offset or mismatch
  • Excess or inadequate weld reinforcement

These defects, otherwise called discontinuities, may cause premature failure of the welds. The causes of this failure include an increase in stress within the weld and a decrease in strength of the weld joints.

Moreover, these welds may start getting damaged over time due to improper use of welding technologies and environmental conditions. At times, a minute flaw may turn out to be a larger defect.

Hence, the welds should be checked for quality, strength, safety, and reliability.

To sustain the quality of welds for their intended application, they should be inspected in detail during their manufacture. There are specific codes and standards for various welding applications. These codes determine the acceptable level of weld defects depending on the application. They can be collected from various sources. 

Several dimensional requirements such as length and weld location are usually established during design measurements. Else, these standards can be extracted from already proven designs that had met the quality requirements. 

Hence, the first criteria to assess the weld quality is to select the right standards according to the application. Next, the characteristics of the given weld material should be compared with these standards using an inspection method. 

What are the various methods of welding inspection?

Welds can be inspected either by destructive or non-destructive methods.

Destructive methods can alter the properties of the sample product while testing. They are time-consuming. These destructive methods include fillet-weld break test, tensile strength break test, transverse tension tests, free bend test, backbend test, macro etch testing, nick break test, and guided bend test.

However, non-destructive methods do not alter the properties of the sample product while testing. These methods can also assess the internal weld defects. They save our money and time. The common non-destructive methods include visual testing, ultrasonic testing, and X-ray inspection.

Visual inspection

Visual inspection is the easiest and the most cost-effective method. However, most of the discontinuities are not visible to our naked eye. They often remain within the internal parts of the welds. A highly qualitative weld should ensure both external and internal quality. This is where the other two methods play a vital role.

Ultrasonic testing

Ultrasonic testing (UT) makes use of high-frequency ultrasonic waves produced by the laser. When a beam of ultrasonic waves is directed to the sample, it usually penetrates. If there is any weld defect, these waves halt and reflect back to their origin. These returned signals are displayed on an oscilloscope screen. 

This method works on all ferrous and nonferrous materials, plastics, and metals. It is comparatively quicker to detect all types of defects including thicker section, deep finer section, surface, as well as subsurface flaws. 

A trained professional is required to interpret the amplitude-tuned data and spikes displayed on the screen. This portable method can measure the weld thickness, control spot welds, and determine lamination-like flaws, submerged-arc weld as well as friction stir weld. It can also detect the type, length, location, and position of these flaws. But this procedure requires reference standards to calibrate the instrument and characterize flaws. Moreover, it is difficult to inspect thin, rough, and irregular-shaped small objects. It is also tough to assess cast iron as well as similar coarse-grained metals due to low sound transmission and high noise signals.

X-ray inspection test

X-ray inspection test makes use of highly penetrating X-rays emitted by an X-ray tube. When these rays are passed through the sample object, there will be a variation in its absorption levels depending on its thickness and density. If there is any defect like crack or porosity, there occurs a change in thickness. And that specific area will appear as dark outlines on the final photographic film. 

Low-density inclusions like slag appear as dark areas; whereas, high-density inclusions like tungsten will appear lighter. Hence, these defects are determined by checking the variation in density of the final image. 

In the case of digital radiography, a flat panel detector is used instead of this film. Similarly, the final image will be displayed on the computer screen in real-time. This X-ray weld inspection test can be applied to all sample materials including complicated welds. 

Film-based radiography may require the help of an experienced technician to interpret the results. However, there is no need for an experienced technician for digital radiography. But the technician should be qualified as there are many safety considerations while performing X-ray testing. 

What are the advantages of the X-ray weld inspection test?

Welds are used in most of the sectors such as military, aerospace, petrochemicals, manufacturing, packaging, waste management, automotive, marine, transportation, power, offshore, and medical devices. Hence, it is mandatory to sustain the quality of welds by performing an X-ray weld inspection test. 

Here is the list of advantages of using X-ray weld inspection test:

  • Compared to other testing methods, the X-ray weld inspection test is superior due to its ease of use. 
  • The radiographic method can identify even the location, shape, position, and type of defects even if they are smaller. It can determine voids, inclusions, porosity including scattered porosity, planar cracks, and delamination in the interior portion of the welds.
  • This X-ray weld inspection test can be used on both sides of the welded joint. It can inspect any type of sample material with varied densities, thicknesses, and volumes as well. It can also determine variations in composition. It can detect surface, subsurface, and internal discontinuities. This procedure can easily inspect assembled components as well. 

How digital radiography is better than film radiography?

Furthermore, digital radiography has more advantages compared to the film type. 

  • Digital radiography involves lesser exposure and inspection time with rapid interpretation. Although it’s more expensive, it reduces the probability of errors due to high efficiency. The results are reproducible, stored, and can be electronically transferred easily and quickly. 
  • Digital radiography can determine weld repairs, the presence of foreign objects, and the possibility of corrosion under insulation. Moreover, it produces high-quality digital images by removing the noise.
  • It can examine fiber-reinforced parts and composites. It can also evaluate the quality of a weld with multiple thicknesses in a single shot.
  • Unlike Film type, digital radiography does not involve the use of consumables or chemicals. Hence, it is eco-friendly. This X-ray weld inspection test doesn’t require any darkroom film processing or battery changes. This technique is highly recommended since it involves additional functions such as noise removal, contrast, and vision improvement.
  • This X-ray weld inspection test helps in measuring the dimensions and angles of the sample without any dissection.
  • This X-ray weld inspection test can deliver a permanent record of weld quality so that it can be easily interpreted by a trained technician.
  • Only a minimum or no surface preparation is required
  • Easily portable


What’s the upshot then? The application of the X-ray weld inspection test is highly recommended for weld manufacturers due to its improvement in productivity, reliability, and ease of use.

The X-ray system can effectively assess the quality of welds by detecting their discontinuities during weld manufacture.  

Hence, the X-ray is a better-quality guarantor than other inspection methods to inspect welds in many industries such as automotive, marine, aerospace, etc.

Are you looking out for a customized X-ray weld inspection system that can develop high-resolution image quality with an automated result? In that case, the X-ray equipment should have a high-quality X-ray tube, digital flat panels, and professional image software.

Don’t miss to contact UNI X-ray company who is renowned for developing reliable real-time hi-tech X-ray equipment to assess the welds accurately!