Weld Inspection & Quality Control Flashcards

What is the main purpose of visual inspection in welding?

Answer: Identify surface defects

Visual inspection is the most fundamental and often the first non-destructive testing (NDT) method applied to welds. Its primary purpose is to detect and evaluate surface discontinuities such as cracks, porosity, undercut, and incorrect weld size or profile that are visible to the naked eye or with simple magnification. This initial check helps ensure the weld meets specified quality standards before further, more complex inspections.

Which tool is commonly used in weld visual inspection?

Answer: Weld gauge

A weld gauge is a specialized measuring tool designed specifically for inspecting various dimensions of a weld. It can accurately measure parameters such as fillet weld leg length, throat thickness, undercut depth, crown height, and porosity size. This makes it an essential tool for visual inspection to ensure welds conform to specified dimensions and quality standards.

What is the purpose of radiographic testing (RT) in weld inspection?

Answer: Find internal defects

Radiographic testing (RT) is a non-destructive testing method that uses X-rays or gamma rays to penetrate the weld material. By analyzing the resulting image (radiograph), inspectors can detect internal discontinuities such as porosity, inclusions, lack of fusion, and internal cracks that are not visible on the surface. This method provides a permanent record of the weld's internal integrity.

Which defect appears as a gap at the weld root?

Answer: Incomplete penetration

Incomplete penetration, also known as lack of penetration, occurs when the weld metal fails to extend through the full thickness of the joint. This results in a gap or unfused area at the root of the weld, significantly reducing the strength and integrity of the joint. It is a critical defect that can lead to premature failure under stress.

Which NDT method uses sound waves to detect weld flaws?

Answer: Ultrasonic testing

Ultrasonic testing (UT) is a non-destructive testing method that uses high-frequency sound waves to detect internal and surface flaws in materials. A transducer emits sound waves into the weld, and by analyzing the reflected echoes, inspectors can determine the location, size, and type of discontinuities such as cracks, voids, and inclusions. This method is highly effective for detecting subsurface defects.

What is porosity in a weld?

Answer: Gas-filled cavities

Porosity in a weld refers to small, gas-filled cavities or voids within the weld metal. These cavities are formed when gases, such as hydrogen, oxygen, or nitrogen, become trapped in the molten weld pool as it solidifies. Porosity can weaken the weld, reduce its ductility, and potentially lead to premature failure under stress.

Which document outlines the specific inspection procedures for a weld project?

Answer: WPS

A Welding Procedure Specification (WPS) is a formal written document that provides detailed instructions for performing a weld. It outlines all essential and non-essential variables, including joint design, filler material, welding process, preheat, and post-weld heat treatment. The WPS also specifies the required inspection procedures and acceptance criteria, ensuring consistency and quality throughout the welding project.

Which type of discontinuity is caused by improper cooling rates?

Answer: Cracking

Cracking in welds, particularly hydrogen-induced cracking or solidification cracking, is often caused by improper cooling rates. Rapid cooling can induce high residual stresses and prevent hydrogen from diffusing out of the weld metal, leading to brittle fracture. Controlling preheat, interpass temperature, and post-weld heat treatment helps manage cooling rates and minimize the risk of cracking.

What is the goal of post-weld inspection?

Answer: Verify code compliance

The primary goal of post-weld inspection is to ensure that the completed weld meets all specified quality standards, engineering requirements, and applicable welding codes or standards (e.g., AWS, ASME). This involves checking for defects, verifying dimensions, and confirming that the weld is fit for its intended purpose. Compliance ensures the structural integrity and safety of the welded component.