Hot-rolled steel includes hot-rolled steel coils, hot-rolled steel sheets, and hot-rolled steel strips. Hot rolled steel refers to undergoing a hot rolling process at a high temperature. Hot-rolled steel supplies you with high strength, and good weldability, easy to process. Hot-rolled steel is widely used in construction, machinery, automobile, shipbuilding, petrochemical, and other industries.
What is Hot-Rolled Steel?
Definition
Hot-rolled steel is steel produced by heating steel billets to above their recrystallization temperature and then plastically deforming them using the pressure of a rolling mill. The high temperature increases the plasticity of the billet, making it easier to form, and the rolling process also refines the grain size.
Hot-rolled steel products possess both good strength and toughness, have high production efficiency, and relatively low cost, making them a fundamental steel material in construction, bridges, shipbuilding, vehicle chassis, machinery, and other fields.
Q235B Hot Rolled Carbon Steel Coils
Hot Rolled Steel Strip
Hot Rolled Steel Sheet
Surface Characteristics
The surface is slightly rough, with streaks/patches of oxide scale formed by high-temperature oxidation.
It has a good balance between plasticity and strength/toughness, and excellent machinability.
Compared to cold-rolled steel, its dimensional accuracy is slightly lower.
The production process is simple, and the cost is relatively low.
Defect Characteristics: Periodically appearing uneven marks, generally uniform in size and shape, with an irregular appearance.
Causes: Roll fatigue or insufficient hardness leading to surface depressions, or foreign matter adhering to the roll surface forming protrusions that are pressed into the steel plate surface during rolling/finishing.
2. Surface Inclusions
Defect Characteristics: Spot-like, blocky, or strip-shaped non-metallic impurities on the surface, mostly reddish-brown, yellowish-brown, grayish-white, or grayish-black in color.
Causes: Subsurface inclusions on the slab are exposed during rolling, or original inclusions remain on the slab surface; refractory materials, slag, and other non-metallic substances from the heating furnace fall onto the slab surface and are pressed in during rolling.
HR Steel Surface Inclusion
3. Iron Oxide Scale
Defect Characteristics: Localized or overall oxide scale adheres to the steel plate surface, appearing black or reddish-brown. Some parts are easily detached, while others are pressed into the slab and difficult to remove; morphologies include reddish-brown scale, blocks, bands, lines, wood grain patterns, meteoroid patterns, etc., with varying depths of indentation.
Causes: Excessive slab heating duration, overly high temperatures, or strong oxidizing atmospheres generate scale that is difficult to remove. Improper vertical roller configuration, insufficient water pressure in high-pressure descaling pipes, blockages, or angle deviations cause scale to be pressed into the slab before removal.
Iron Oxide
4. Uneven Thickness
Defect Characteristics: The thickness of the steel plate varies across different parts, exceeding the allowable range, with some areas exceeding the thickness standard.
Causes: Improper roll gap adjustment or roll configuration; uneven wear of the rolls and bearing bushes; uneven temperature distribution during slab heating.
5. Pockmarks
Defect Characteristics: Small, localized or continuous pits of varying size and depth on the surface.
Causes: Severe oxidation during slab heating; the resulting scale is pressed into the surface during rolling and subsequently detaches, forming pits.
Hot Rolled Steel Pockmarks
6. Flat roll
Defect Characteristics: The ends of the steel coil are elliptical or flattened, more common in softer or thinner coils.
Causes: The steel coil is subjected to severe impact during hoisting; the coil is rolled too tightly, the temperature is too high, and it is laid flat on the ground or stacked and compressed.
Wanzhi Steel: China’s Professional Hot-Rolled Steel Supplier
Our Advantages
We have a rigorous inspection process, including testing of appearance, performance, and composition, to ensure our products are defect-free and of high quality.
With over 14 years of production and export experience, we boast high production efficiency, enabling us to deliver high-quality products quickly.
As a professional supplier, we are certified by ISO 9001, ISO 14001, and other standards. Our company adheres to the principle of honest cooperation and has gained long-term clients from many countries.
How to Cut Hot-Rolled Steel Coils into Hot-Rolled Steel Plates
Hot-rolled steel is a widely used metal material, that plays a key role in construction, machinery, automobile, shipbuilding, petrochemical, and other industries, but it is inevitable to encounter some problems in the actual operation process. The above are the common problems of hot-rolled steel summarized by our company according to years of production and sales experience. If you have any questions or purchasing needs for hot-rolled steel, please feel free to contact us.
