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.
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.
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.
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.
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.
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 is the most widely used NDT method for shipbuilding plate inspection. High frequency sound waves penetrate the steel and reflect back when encountering defects.
Internal cracks
Laminations
Inclusions
Blowholes
Delaminations after rolling
UT is essential for thicker plates, especially DH36 and EH36 grades used in vital offshore components.
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.
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.
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 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.
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 uses electromagnetic induction to identify surface flaws, corrosion, and conductivity variations.
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 remains one of the most fundamental NDT methods. It ensures the surface condition meets shipbuilding standards before more advanced inspections are performed.
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.
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 is performed at various stages of steel production to ensure quality consistency.
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.
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.
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.
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.