Stainless Steel Surface Finishes: The Ultimate Guide

Stainless steel, a material renowned for its corrosion resistance and durability, is a popular choice for a wide range of applications. However, it’s not just the inherent properties of the steel that make it so useful; it’s also the various surface finishes that can be applied to stainless steel to further enhance its performance and appearance. In this ultimate guide, we’ll explore the various types of stainless steel surface finishes, their unique characteristics, and the best applications for each finish. Whether you’re a professional working with stainless steel on a daily basis or someone who wants to understand more about this material’s surface finishes, this guide is for you.

Stainless Steel Surface Finishes – NO. 1 FINISH

The No.1 surface is achieved by hot rolling the sheet and strip, followed by heat treatment and pickling. It removes the black iron oxide generated during hot rolling and heat treatment by pickling or similar processing methods. This surface is silver-white and has no luster. It is mainly used in heat-resistant and corrosion-resistant industries that do not require a shiny surface, such as the alcohol industry, chemical industry, and large containers. fiber laser engraver

Stainless Steel Surface Finishes – No.2D FINISH

The No.2D surface is a non-oxidized, cold-rolled, non-glossy surface. After cold rolling, it only undergoes heat treatment and pickling without gloss smoothing. The brightness of the surface depends on the degree of cold rolling deformation, the surface roughness of the work roll in the final pass, and the pickling method used to remove oxidation.

The No.2D surface also includes a rough surface obtained by further smoothing with a roughing roll on the basis of the above surface. The roughing roll is a roll with a rough surface created by a special process that forms numerous hardened points of phase transformation on the roll surface. During the flattening process, an uneven surface structure with both rigid and flexible features is achieved on the steel sheet surface. This is also a non-glossy surface. This surface is particularly suitable for deep drawing and can improve the friction and contact conditions between the steel sheet and the mold, facilitate material flow, and improve the forming quality of the workpiece.

No.2D stainless steel with this surface is widely used in building curtain walls, especially in areas that do not require reflection. The roughness Ra value of this surface measured by instruments is about 0.4～1.0μm.

Stainless Steel Surface Finishes – No.2B FINISH

The difference between the No.2B surface and the 2D surface is that the No.2B surface is also smoothed with a smoothing roll, making it brighter than the 2D surface. The surface roughness Ra value measured by instruments is 0.1～0.5μm, which is the most common processing type. This stainless steel surface has the broadest applications and is suitable for general purposes in the chemical, paper, petroleum, and medical industries, as well as for building curtain walls.

Stainless Steel Surface Finishes – No.3 FINISH

The No.3 surface is a semi-polished surface. It is a processed surface obtained by polishing the cold-rolled stainless steel of the 2D or 2B surface using a sanding belt with a particle size of 100～120#. The surface roughness Ra value measured by instruments is 0.4～1.5μm. It is suitable for use as building materials, kitchen utensils, and in situations where further finishing is required after manufacturing.

Stainless Steel Surface Finishes – No.4 FINISH

No.4 surface is a finer polished surface than the No.3 surface. It is also processed using a sanding belt with a particle size of 150～180# on the cold-rolled stainless steel of the 2D or 2B surface. The surface roughness Ra value measured by instruments is 0.2～1.5μm. This surface is widely used in restaurant kitchen equipment, medical equipment, container fronts, and is suitable for building cladding and edge finishes on building curtain walls. It is not easy to leave fingerprints on this surface, making it suitable for making steel doors.

Stainless Steel Surface Finishes – 240# and 320# FINISH

The 240# and 320# surfaces are obtained by polishing with a sanding belt with a particle size of 240# or 320#, respectively. These surfaces are suitable for kitchen utensils.

Stainless Steel Surface Finishes – HL FINISH

HL surface steel plate is commonly known as hairline plate. In the Japanese JIS standard, it is stipulated that the continuous hairline grinding surface is obtained by polishing with a sanding belt with a particle size of 150～240#. In China’s GB3280, the stipulation is relatively vague. This surface is mostly used for architectural decoration, such as elevators, escalators, door faces, etc.

Stainless Steel Surface Finishes – No.6 FINISH

The No.6 surface is obtained by further polishing with a Tampico brush or the abrasive material of particle size W63 specified in GB2477 on the basis of the No.4 surface. This surface has a better metallic luster, a gentle surface, weak reflectivity, and no image reflection. It is very suitable for making building curtain walls and edge finishes, and is also widely used as kitchen utensils.

Stainless Steel Surface Finishes – No.7 FINISH

The No.7 surface is obtained by fine polishing with a rotating polishing wheel of particle size 600#, which has a quasi-mirror finish with a high reflectivity. It corresponds to the surface polished with the abrasive material of particle size W50 specified in GB2477. It is mainly used on buildings and decorations.

Stainless Steel Surface Finishes – BA FINISH

The BA surface is obtained by cold rolling and bright heat treatment. The bright heat treatment is annealing under a protective atmosphere that ensures surface oxidation is prevented, preserving the gloss of the cold-rolled surface. Subsequently, a high-precision leveling roll is used for light leveling to improve the surface brightness. This surface is close to a mirror and has a surface roughness Ra value of 0.05～0.1μm measured by instruments. This surface has a wide range of applications and can be used as kitchen utensils, household appliances, medical equipment, automotive parts, and decorations.

Stainless Steel Surface Finishes – No.8 FINISH

The No.8 surface is the highest-reflectivity non-polishing mirror finish processing surface, which is also called 8K board in the stainless steel deep processing industry. Generally, BA material is used as the raw material and only mirror processing is carried out through polishing and buffing processes. After mirror processing, the surface is beautiful and pleasing to the eye, so it is mostly used in decorative aspects such as entrance decoration and interior decoration of buildings.

However, it is also used in places where glass mirrors are prone to breakage and are unsafe, such as road bend mirrors and gymnasium dressing mirrors. Mirror processing is a difficult topic in stainless steel polishing technology, leading to the development of various methods including mechanical, chemical, electrochemical, and fluid mechanical means.

Stainless Steel Surface Finishes – TR FINISH

TR material is also known as hard steel, which means it is a hard material. Its representative steel grades include SUS304, SUS 301, and SUS 301L. It is used in products that require strength and hardness, such as railway vehicles, conveyor belts, springs, and gasket rings. The principle is to utilize the work hardening characteristics of austenitic stainless steel, and increase the strength and hardness of the steel plate through cold processing methods such as rolling. Hard steel uses a few percent to several tens of percent of mild rolling instead of the light flattening of the 2B surface.

No annealing is performed after rolling, so the surface of hard steel is the rolling surface after cold rolling. In addition, in order to perform shape correction and material flattening after cold rolling, most measures are also implemented such as low-temperature annealing and tension leveling using a tension leveling machine. The cold rolling process example is as follows: annealing pickling of the base plate – rolling by rolling machine – annealing pickling or bright annealing – rolling by rolling machine – low-temperature annealing (bright annealing) – tension leveling – finishing.

Stainless Steel Surface Finishes – Embossed FINISH

The embossed surface is a finishing surface with a pattern produced by using etching methods or rolling with a patterned embossing roll. The pattern is pressed onto one side of the steel plate. Most of the embossed patterns are regular geometric shapes, but some are irregular and random. For example, the groove pattern steel plate produced by rolling with a groove-shaped pattern roll not only has artistic effects, but also has anti-skid effects.

Stainless Steel Surface Finishes – Reticulated

In the final pass of hot rolling, using a patterned rolling roll or stamping with No.1 plate, deeper concave and convex patterns can be pressed onto the surface of hot rolled steel plate or No.1 plate. This kind of surface steel plate can be used for flooring in large public places, which is not only anti-skid and durable, but also beautiful. It can also be used in architecture and machinery manufacturing.

Conclusion

Thank you for reading our article and we hope it can help you to have a better understanding of the stainless steel surface finishes. If you want to learn more about stainless steel, we would like to advise you to visit Sino Stainless Steel for more information.

As a leading supplier of stainless steel products across the world, Sino Stainless Steel provides customers with high-quality stainless steel products such as stainless steel strips, stainless steel coils, stainless steel plates, stainless steel sheets, stainless steel bars, and stainless steel wires at a very competitive price.