Standard for ultrasonic testing of forgings

The standards for ultrasonic testing of forgings mainly include "Ultrasonic Testing of Marine Forged Steel Parts" (CB/T 3907-1999) and "General Technical Conditions for Metallurgical Equipment Manufacturing - Ultrasonic Testing of Forged Steel Parts" (YB/Y 036.10-1992). The standard for ultrasonic testing of ship forged steel parts has 

been implemented since June 1, 1999, providing specific operating guidelines and acceptance standards for ultrasonic testing of ship forged steel parts. The General 

Technical Conditions for Manufacturing of Metallurgical Equipment - Ultrasonic Testing Method for Forged Steel Parts is applicable to the ultrasonic testing of carbon 

steel and alloy steel forgings with a thickness or diameter not less than 60 mm in metallurgical equipment, but it is not applicable to the ultrasonic testing of austenitic 

stainless steel forgings and forgings with specialized standards.

Ultrasonic testing technology is a non-destructive testing method that detects internal defects in materials through the propagation characteristics of ultrasonic waves in 

the tested material. There are two types of commonly used ultrasonic flaw detectors: analog signals and digital signals. Among them, the digital signal flaw detector can automatically calculate and save data, providing higher detection accuracy and convenience. During the inspection process, straight probes and oblique probes are two 

common types of probes used for vertical and oblique incidence detection, respectively.

For forgings, ultrasonic testing is an important means to ensure their quality. Different types of forgings (such as shafts, cakes, bowls, cylinders, etc.) require different te-

sting methods and parameters due to their different forging processes and defect types. For example, defects in shaft forgings are often parallel to the axis, making it 

suitable to use a straight probe to detect them radially; Due to the complex defect orientation of cylindrical forgings, in addition to straight probes, oblique probes are 

also needed for detection.

For forgings, ultrasonic testing is an important means to ensure their quality. Different types of forgings (such as shafts, cakes, bowls, cylinders, etc.) require different 

testing methods and parameters due to their different forging processes and defect types. For example, defects in shaft forgings are often parallel to the axis, making 

it suitable to use a straight probe to detect them radially; Due to the complex defect orientation of cylindrical forgings, in addition to straight probes, oblique probes 

are also needed for detection.

In addition, the defects that may occur during the machining process of forgings include casting defects, forging defects, and heat treatment defects, and the types 

and distribution of these defects have a direct impact on the selection of testing methods and parameters. For example, white spots and cracks are common defects 

in forgings, and they have a significant impact on the mechanical properties of forgings. Therefore, special attention should be paid during non-destructive testing.

Forgings should generally undergo longitudinal wave testing, and simple forgings should also undergo transverse wave testing. However, the scanning location and 

acceptance criteria should be agreed upon by both the supply and demand parties. The scanning method is as follows:

1. In principle, forgings should be tested in two perpendicular directions to detect the full volume of the forgings as much as possible. Other shapes of forgings can 

also be used as a reference

2. Scanning scope: The entire surface of the forging should be continuously and comprehensively scanned

3. Scanning speed: The probe's movement speed should not exceed 150mm/s

4. The scanning cover should be at least 15% of the probe diameter

When the detection thickness of the forging is greater than 400mm, the detection should be carried out from the opposite two ends。The verification of flaw detection 

sensitivity includes:In principle, a large flat bottom is used to determine the sensitivity of the flaw detection using the calculation method. 

1.For workpieces limited by geometric shape and with defects in the near-field area, the specimen method can be used

2. Use the bottom wave method to correct sensitivity, and the position of the correction point should be selected as a defect free and intact area on the workpiece

3. Surface compensation: For workpieces with a curved detection surface that cannot be measured using the bottom wave method, a reference test block with the same 

or similar curvature (0.7-1.1 times) as the workpiece should be used; Alternatively, a probe with a small diameter chip can be used to make the length of the near-field 

region less than or equal to 1/4 of the workpiece radius, which eliminates the need for surface compensation

4.The sensitivity of the flaw detection shall not be lower than the equivalent diameter of 2mm

Determination of defect equivalent

1. Determine defect equivalent using AVG curve and calculation method

2.When calculating the defect equivalent, when the material attenuation coefficient exceeds 4dB/m, correction should be considered

3.Determination of material attenuation coefficient