High Strength NK Shipbuilding Steel Plate Grade AH32 DH32 AH36 EH36 With Certification

High Strength NK Shipbuilding Steel Plate Grades AH32, DH32, AH36, and EH36

The high strength NK shipbuilding steel plates of grades AH32, DH32, AH36, and EH36 are of significant importance in the shipbuilding industry. These steel plates are characterized by their superior properties and reliable performance.

Chemical Composition:
The chemical composition of these steel grades is precisely formulated to achieve the desired mechanical and physical properties. They typically contain elements such as carbon, manganese, silicon, sulfur, and phosphorus in controlled proportions. The specific contents of these elements vary within defined ranges to meet the standards set by the NK classification society.

Mechanical Properties:
These steel grades exhibit excellent mechanical properties. The AH32 grade offers a yield strength of at least 315 MPa, a tensile strength ranging from 440 to 590 MPa, and an elongation of not less than 22%. The DH32 grade shows similar characteristics with certain enhancements. The AH36 grade provides a higher yield strength of at least 355 MPa and a tensile strength ranging from 490 to 630 MPa, along with an elongation of at least 21%. The EH36 grade further improves the mechanical performance.

Implementation Standards:
These steel plates adhere to the strict standards and specifications established by the NK (Nippon Kaiji Kyokai) classification society, ensuring their quality and suitability for use in shipbuilding applications.

Production Process:
The production of these steel plates involves a series of meticulous processes. It begins with the selection of high-quality raw materials and continues through melting, casting, hot rolling, and controlled cooling. Quality control measures are implemented at each stage to guarantee that the final products meet the demanding requirements of the NK standards.

In conclusion, the high strength NK shipbuilding steel plates of grades AH32, DH32, AH36, and EH36 are essential materials in the construction of ships, providing the necessary strength, durability, and safety to withstand the challenging marine environment.

The production process of high-strength NK marine steel typically includes the following steps:

1. Raw material selection: High-quality raw materials are selected, including elements such as iron, carbon, manganese, and silicon, to ensure the basic properties of the steel.
2. Smelting: The raw materials are smelted in a furnace. By precisely controlling the temperature, time, and other process parameters, various elements are fully fused to form the required molten steel.
3. Refining: Further remove impurities from the molten steel to increase the purity of the steel and improve its performance.
4. Casting: The refined molten steel is cast into billets.
5. Heating: The billets are heated to reach the appropriate rolling temperature.
6. Rolling: Through multiple passes of the rolling process, the billets are gradually rolled into the desired thickness and shape. During the rolling process, parameters such as rolling force, rolling speed, and temperature need to be strictly controlled to ensure the dimensional accuracy and performance of the steel.
7. Controlled cooling: Appropriate cooling methods and cooling rates are adopted to enable the steel to obtain the ideal microstructure and performance during the cooling process. The control of the cooling rate has an important influence on the strength, toughness, and other properties of the steel.
8. Heat treatment (if necessary): It may include heat treatment processes such as normalizing and tempering to further adjust the microstructure and properties of the steel.
9. Quality inspection: Various quality inspections are conducted on the produced marine steel, including chemical composition analysis, mechanical property tests, and non-destructive testing, to ensure that it meets the standards and requirements of high-strength NK marine steel.

The specific production process may vary depending on the equipment, technology, and product requirements of the steel mill. For example, in the production process of a certain type of high-strength marine section steel, firstly, a rectangular billet is widened into a flat billet through the first blooming mill (bd1). The process involves pressing grooves on the slab first and then flattening the protrusions beside the grooves. Through zonal rolling, the elongation of the rolled piece is reduced and the width expansion is increased. Compared with the conventional width expansion method, the width expansion amount can be 30% more. Then, the flat billet is rolled into a symmetrical profile through the second blooming mill (bd2). This profile has thick ends and a thin middle, and the plate part shows a wavy shape. After rolling, the profile is immersed in a quenching medium for forced cooling to a specific temperature and held for a period of time, and then heated and held again. Subsequently, the profile is rolled into the initial material through two tandem two-high rolling mills (drdf). The initial material consists of two symmetrical web-connected bulb flats. There is a depression at the connection of the two symmetrical bulb flat webs, and the thickness at the depression is less than that at the bulb flat web. The included angle on the two symmetrical bulb flat webs is less than 180°. Then, the initial material undergoes combined air cooling and wind cooling. The cooling process is carried out in a specific cooling bed workshop, which adopts stepped gas cooling technology, ensuring the cooling rate and balanced cooling, making the surface of the bulb flat cool evenly with small bending deformation. Finally, the cooled initial material is split and straightened.

 

NK GRADE high strength property

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