S355ML steel plate implementation standards, production process flow introduction, characteristics and applications of S

Posted by BAOWI STEEL MANUFACTURING CO.,LTD on September 12th, 2024

S355ML steel plate is a low-alloy high-strength structural steel widely used in various engineering fields. The following is a comprehensive analysis of S355ML steel plate:

1. Naming and standards of S355ML steel plate

The grade of S355ML steel plate consists of several parts, each of which has its specific meaning:

S: Indicates that the steel plate is European standard structural steel, that is, the steel is mainly used for structural purposes, such as buildings, bridges, mechanical parts, etc.

355: Indicates that when the thickness of the steel plate is less than 16mm, its minimum yield strength is 355MPa. Yield strength is the stress limit at which the material begins to undergo plastic deformation when subjected to external force, and is a key indicator for evaluating the strength of the material.

M: In S355ML, M does not directly represent "hot-rolled state", but is related to the production process, and is sometimes interpreted as "Thermo-Mechanical Rolling". This rolling process can improve the mechanical properties of steel. However, it should be noted that different sources may interpret M slightly differently, and some directly regard it as an indication of hot-rolled state.

L: Indicates that the steel still has good impact toughness at a temperature not lower than -50°C. This is a very important performance requirement for structural parts used in cold environments.

Implementation standard: Follow European standard EN 10025-4.

2. Chemical composition of S355ML steel plate

Element Content range (%)

Carbon (C) ≤0.20 (some data give ≤0.14 or 0.12~0.20)

Silicon (Si) ≤0.50

Manganese (Mn) 0.901.65 (some data give 0.401.65)

Phosphorus (P) ≤0.035 (some data give ≤0.025)

Sulfur (S) ≤0.035 (some data give ≤0.020)

Chromium (Cr) ≤0.30

Nickel (Ni) ≤0.50

Molybdenum (Mo) ≤0.10 (some data give ≤0.50)

Niobium (Nb) 0.005~0.05

Vanadium (V) 0.01~0.12

Titanium (Ti) 0.006~0.05

Other Copper (Cu) ≤0.40, nitrogen (N) ≤0.015, aluminum (Al) ≤0.03%, etc.
III. Mechanical properties of S355ML steel plate

The mechanical properties of S355ML steel plate are one of its important characteristics as a high-strength low-alloy structural steel, which are specifically manifested in the following aspects:

1. Yield strength

Definition: Yield strength is the stress limit at which the material begins to undergo plastic deformation when subjected to external force.

Value: For S355ML steel plate, its yield strength varies in different thickness ranges, but is not less than 320MPa, especially when the thickness of the steel plate is less than 16mm, its minimum yield strength is 355MPa. This value is much higher than the strength level of ordinary carbon structural steel.

2. Tensile strength

Definition: Tensile strength is the maximum stress that a material can withstand during stretching.

Value: The tensile strength of S355ML steel plate ranges from 430-630MPa, depending on the specific production process and heat treatment method. This high tensile strength enables S355ML steel plates to withstand greater tension and is suitable for structural parts that require high load-bearing capacity.

3. Elongation at break

Definition: Elongation at break is the degree of plastic deformation that a material undergoes before breaking during the tensile process, expressed as a percentage.

Value: The elongation at break of S355ML steel plates is not less than 22%, which means that the steel plates can undergo large plastic deformation before breaking and have good toughness.

4. Impact toughness

Definition: Impact toughness is the ability of a material to resist breaking under impact loads.

Value: S355ML steel plates still have good impact toughness at low temperatures, such as the Charpy V-notch impact energy at -20°C or -40°C can reach or exceed 27J. This feature enables S355ML steel plates to maintain stable performance in cold environments and is suitable for structural parts that need to withstand low-temperature impact loads.

5. Welding performance

Description: S355ML steel plates have good welding performance and are easy to perform various welding processes. Its lower carbon equivalent reduces the risk of cracks and deformation during welding, and it is not easy to embrittle after welding, which ensures the quality and reliability of the welded joint.

In summary, the mechanical properties of S355ML steel plate include high strength, high toughness, good welding performance and impact resistance. These excellent properties make S355ML steel plate widely used in bridges, construction, machinery manufacturing and other fields. It should be noted that the specific mechanical properties may vary depending on the production standards, manufacturers and uses, so in practical applications, it should be selected according to specific needs.

4. Characteristics and Application of S355ML Steel Plate

S355ML steel plate, as a low-alloy high-strength structural steel, has many excellent characteristics and a wide range of applications. The following is a detailed analysis of its characteristics and applications:

Characteristics

1. High strength:

When the thickness of S355ML steel plate is less than 16mm, its minimum yield strength is 355MPa, which reflects its high strength characteristics. This enables it to maintain structural stability and safety in an environment with high loads and stresses.

2. Good toughness:

The steel plate can still maintain good impact toughness when the temperature is not lower than -50℃, indicating that it has good low-temperature toughness. This feature enables S355ML steel plate to still perform excellent performance in cold environments.

3. Excellent welding performance:

S355ML steel plate has good welding performance and is easy to carry out various welding processes. Its low carbon equivalent reduces the risk of cracks and deformation during welding, and it is not easy to embrittle after welding, ensuring the quality and reliability of the welded joint.

4. Good processing performance:

The steel plate is easy to cut, bend and stamp, and can meet the needs of structural parts of different shapes and sizes.

5. Corrosion resistance:

After proper anti-corrosion treatment (such as painting, galvanizing, etc.), S355ML steel plate can withstand erosion in various harsh environments for a long time, such as moisture and corrosion.

6. Stable chemical composition and mechanical properties:

The chemical composition and mechanical properties of the steel plate meet the requirements of European standard EN10025-4, ensuring the stability and reliability of its quality.

Application

Due to its excellent performance characteristics, S355ML steel plate has been widely used in many fields:

1. Construction field:

Used for load-bearing structures of high-rise buildings, beams and columns of large industrial plants, etc. Its high strength and good toughness can ensure the safety and stability of building structures.

2. Bridge field:

Used for manufacturing main beams, cross beams and supporting structures of bridges. In large-span bridges and bridges with complex structures, the high strength and good welding performance of S355ML steel plates are particularly important.

3. Machinery field:

Used for manufacturing bases, brackets, etc. of various heavy machinery and equipment. Its high strength and good processing performance can meet the high requirements of the machinery manufacturing industry for material performance and quality.

4. Vehicle field:

Used for manufacturing chassis and frames of heavy-duty vehicles. The high strength and good toughness of S355ML steel plate can ensure the safety and stability of the vehicle during driving.

Marine engineering:

Applicable to marine platforms, ship structures, etc. Its good corrosion resistance and resistance to marine environmental erosion make S355ML steel plate have a wide range of application prospects in marine engineering.

5. Other fields:

It is also used in storage tanks and containers, transportation equipment, energy fields, such as oil storage tanks, chemical storage tanks, railway vehicles, wind power generation equipment, etc. Its excellent comprehensive performance enables S355ML steel plate to play an outstanding role in many fields.

In summary, S355ML steel plate has become an indispensable and important material in modern industry with its high strength, good toughness, excellent welding performance and wide application fields.

5. Production process of S355ML steel plate

The production process of S355ML steel plate is a complex and delicate process involving multiple key steps to ensure that the quality and performance of the final product meet the standard requirements. The following is a detailed analysis of the production process of S355ML steel plate:

1. Raw material preparation

Material selection: High-quality iron ore and alloy elements are selected as raw materials. These raw materials need to meet the requirements of the chemical composition of S355ML steel plate to ensure the performance of the final product.

Batch control: During the preparation process, the raw materials are precisely batched to ensure the stability of the chemical composition during the smelting process.

2. Melting and refining

Smelting process: The raw materials are placed in a high-temperature smelting furnace for smelting. During the smelting process, the appropriate smelting temperature needs to be maintained to ensure the full melting of the raw materials and the progress of chemical reactions.

Refining method: Refining methods such as oxygen blowing and vacuum treatment are used to remove impurities in the molten steel and improve the purity of the steel. These methods help to reduce the non-metallic inclusions and gas content in the steel and improve the quality of the steel.

3. Casting

Continuous casting or mold casting: After the smelting is completed, the molten steel is injected into the mold of the continuous casting machine or the mold casting process is used to cool and solidify it to form a continuous billet or casting. The continuous casting process has the advantages of high production efficiency, low cost and stable product quality.

4. Hot rolling

Preheating and rolling: After the continuous casting billet is preheated to the appropriate temperature, it is pressed into the desired slab shape by the hot rolling mill roller. During the hot rolling process, the slab can be heated and kept warm and rolled according to requirements to obtain the required thickness and width.

Heating and keeping warm: Heating and keeping warm helps to improve the structure and performance of steel, and improve its strength and toughness.

5. Controlled rolling and normalizing

Controlled rolling: The slab is controlled by controlling the hot rolling temperature and speed. This step helps to adjust the crystal structure and mechanical properties of the steel and reduce residual stress.

Normalizing: Normalizing is a process of recrystallizing the crystals of the steel and forming the required mechanical properties through heating and cooling. When S355ML steel plate is heat treated, the recommended normalizing temperature is 890℃-950℃. Normalizing can further improve the strength and toughness of the steel and improve its welding performance.

6. Finished product processing

Finishing and cutting: The steel plates after normalizing are trimmed, cut and processed, such as trimming, cutting into fixed sizes, etc., to meet the specific requirements of customers.

Surface treatment: The steel plates are surface treated as needed, such as sandblasting, painting, etc., to improve their corrosion resistance and aesthetics.

7. Inspection and quality control

Quality inspection: The finished steel plates are inspected for quality, including chemical composition analysis, physical property testing, and geometric dimension measurement. These inspection items help ensure that the quality and performance of the steel plates meet the standard requirements.

Quality control: During the production process, strict quality control measures are implemented, such as regular sampling and recording of production data, to ensure the stability of the production process and the reliability of product quality.

Precautions

The specific production process may vary depending on the production plant, equipment and technical conditions. Therefore, in the actual production process, it may also need to be adjusted and optimized according to the specific situation.

When selecting and using S355ML steel plates, relevant material manuals and technical specifications should be referred to ensure that they meet specific engineering requirements.

In short, the production process of S355ML steel plate is a complex process involving multiple links and steps. Through strict raw material preparation, smelting and refining, casting, hot rolling, controlled rolling and normalizing treatment, finished product processing, inspection and quality control, the quality and performance of S355ML steel plate can be ensured to meet the standard requirements and meet the needs of various engineering applications.

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