Non-Destructive Testing NDT for AH36 DH36 EH36 Steel Plate Quality Assurance

In the global shipbuilding industry, high strength marine steel plates such as AH36, DH36, and EH36 must meet strict quality and safety standards. These steels are widely used in hull construction, offshore platforms, subsea equipment, and structural components that operate under extreme loads and challenging marine environments. To guarantee the reliability of these critical materials, Non Destructive Testing NDT plays an essential role in ensuring plate integrity without compromising the material’s usability. Leading manufacturers such as sakysteel integrate advanced NDT technologies into their production process to deliver shipbuilding steel plates that fully comply with international classification requirements.

This article explores the importance of NDT, the different methods used for AH36 DH36 EH36 steel plates, and how these testing techniques contribute to high level quality assurance in marine engineering.

Importance of NDT in Shipbuilding Steel Plate Manufacturing

Shipbuilding steel plates are subjected to dynamic loads, impact forces, temperature fluctuations, and long term fatigue conditions. Any internal or surface defect can pose serious risks, including structural failure, crack propagation, or reduced service life. NDT ensures that these steel plates are free from defects while preserving their structural integrity.

Why NDT Is Critical for AH36 DH36 EH36

• Ensures compliance with ABS, DNV, LR, BV, CCS

• Detects invisible internal defects

• Prevents welding failures during ship construction

• Improves safety and operational reliability

• Helps shipyards avoid costly repairs and downtime

• Provides full traceability and documentation

NDT is therefore a fundamental part of quality assurance for all marine grade plates.

Overview of AH36 DH36 EH36 Steel Plate Requirements

AH36, DH36, and EH36 are high strength shipbuilding steels with a minimum yield strength of 355 MPa, excellent weldability, and specific impact toughness requirements. Their performance standards require strict inspection procedures throughout production.

Impact Toughness Requirements

• AH36: Tested at 0 degrees Celsius

• DH36: Tested at minus 20 degrees Celsius

• EH36: Tested at minus 40 degrees Celsius

Because toughness and internal soundness are vital for these grades, NDT becomes essential to detect and prevent structural weaknesses.

Types of Non Destructive Testing Used for Shipbuilding Steel Plates

Multiple NDT methods are applied depending on plate thickness, classification rules, and customer specifications. The most commonly used techniques include Ultrasonic Testing UT, Magnetic Particle Inspection MPI, Radiographic Testing RT, Eddy Current Testing ECT, and Visual Inspection VT.

Below is a detailed explanation of each method.

Ultrasonic Testing UT for Internal Defect Detection

Ultrasonic Testing is the most widely used NDT method for shipbuilding plate inspection. High frequency sound waves penetrate the steel and reflect back when encountering defects.

UT Detects

• Internal cracks

• Laminations

• Inclusions

• Blowholes

• Delaminations after rolling

UT is essential for thicker plates, especially DH36 and EH36 grades used in vital offshore components.

Benefits of UT

• High accuracy and sensitivity

• Inspection of the entire plate volume

• Immediate results for fast production workflow

• Complies with major classification society requirements

UT is a standard practice in advanced steel mills such as sakysteel to ensure internal soundness.

Magnetic Particle Inspection MPI for Surface and Near Surface Flaws

MPI is used to detect surface breaking and slightly subsurface defects. When magnetic fields are applied to the steel surface, discontinuities attract magnetic particles, revealing defect indications.

MPI Is Effective for Detecting

• Surface cracks

• Grinding cracks

• Welding flaws

• Seams and laps on rolled plates

MPI is ideal for areas around edges, weld zones, or surfaces that require forming and bending during shipyard fabrication.

Radiographic Testing RT for Welded Joints and Plate Sections

Radiographic Testing uses X rays or gamma rays to detect internal defects through image capture. RT is commonly applied for testing weld quality in shipbuilding but can also be used on plate sections.

RT Detects

• Porosity

• Inclusions

• Shrinkage cavities

• Cracks

• Lack of penetration in welds

RT provides a permanent record of inspection results, making it valuable for documentation and compliance.

Eddy Current Testing ECT for Surface Condition Analysis

Eddy Current Testing uses electromagnetic induction to identify surface flaws, corrosion, and conductivity variations.

ECT Is Useful For

• Detecting thin surface cracks

• Measuring coating thickness

• Identifying early stage corrosion

• Verifying heat treatment conditions

Although not commonly used for thick plates, ECT is helpful in certain shipbuilding applications requiring surface verification.

Visual Testing VT as the First Level of Inspection

Visual Testing remains one of the most fundamental NDT methods. It ensures the surface condition meets shipbuilding standards before more advanced inspections are performed.

VT Evaluates

• Surface finish

• Flatness and straightness

• Scaling and surface marks

• Edge condition

• Plate surface defects

VT is always performed early in the inspection process to determine suitability for further NDT procedures.

Acceptance Standards for NDT in Shipbuilding Steel Plates

NDT tests must comply with international classification society rules. These standards define acceptance criteria for AH36 DH36 EH36 plates:

• ABS Rules for Materials and Welding

• DNV OS B101 Metallic Materials

• Lloyds Register Rules for Ship Materials

• CCS GB712 Steel Plate Requirements

• ISO and EN standards for NDT procedures

These rules specify allowable defect sizes, testing frequency, and documentation procedures.

NDT in Production Workflow of Shipbuilding Steel Plates

NDT is performed at various stages of steel production to ensure quality consistency.

Typical Workflow Includes

• Raw material inspection

• UT after rolling to detect laminations

• MPI to verify surface condition

• RT or ECT depending on customer requirements

• Final VT before packaging

• Review of NDT documentation and reports

Combined testing ensures the plates fully meet mechanical and structural properties expected by shipyards.

Benefits of Using NDT for Marine Engineering Projects

NDT significantly increases the reliability and performance of shipbuilding steel plates. Its benefits include:

• Enhanced safety in ship and offshore structures

• Reduction of structural failures

• Full compliance with classification rules

• Improved weldability and formability

• Lower long term maintenance costs

By integrating NDT, manufacturers guarantee that AH36 DH36 EH36 plates perform flawlessly under demanding marine conditions.

Role of Leading Manufacturers in Ensuring NDT Quality

Advanced steel manufacturers play a key role in maintaining reliable NDT standards. Companies such as sakysteel utilize automated testing equipment, calibrated instruments, and trained inspectors to deliver high quality steel plates for global shipyards.

Their integrated NDT systems ensure consistency, traceability, and certification that comply with international marine requirements.

Conclusion

Non Destructive Testing is an indispensable part of ensuring the quality, integrity, and safety of AH36 DH36 EH36 shipbuilding steel plates. Through methods such as UT, MPI, RT, ECT, and VT, manufacturers can detect both surface and internal defects without affecting the usability of the steel. These tests ensure full compliance with classification society requirements, giving shipyards confidence in the material’s performance under harsh marine conditions.

As the shipbuilding industry continues to advance, rigorous NDT standards will remain essential for ensuring reliable and high strength steel plate solutions worldwide.