Properties, finishes and the right choice.
A stainless steel sheet may seem like a standard semi finished product. In practice, the right choice determines how a final product performs, both technically and visually.
In sectors such as high tech, food, pharma and mechanical engineering, it is not just about the material itself, but about the combination of:
the stainless steel grade
the production method, hot rolled or cold rolled
the required surface finish and Ra value
Making the right choices at an early stage prevents unnecessary rework, costs and quality issues later on.
The properties of a stainless steel sheet are determined by its alloy. In practice, four main groups are commonly used:
Austenitic stainless steel, such as 304 and 316
Ferritic stainless steel
Martensitic stainless steel
Duplex stainless steel
This is by far the most commonly used type. Grades such as 304 (1.4301) and 316 (1.4404) are widely applied.
Key characteristics of this group:
good formability, such as bending and deep drawing
good weldability
excellent for grinding and polishing
high corrosion resistance
For applications where cleanability and chemical resistance are critical, such as in the food and pharmaceutical industries, 316 is often the standard.
Depending on the application, other stainless steel grades may also be relevant:
Ferritic stainless steel is more cost effective, but less corrosion resistant
Martensitic stainless steel offers high hardness and is suitable for wear resistant applications
Duplex stainless steel combines high strength with good corrosion resistance
The right choice always depends on the environment and the function of the product.
The production method has a major impact on surface quality and the required post processing.
Hot rolled material is mainly used for thicker plates, from approximately 8 mm and above. The surface is rough and matte, with relatively high roughness.
Typical characteristics:
rough mill scale
surface roughness often higher than Ra 3.0 µm
post processing is almost always required
In practice, this means that a hot rolled stainless steel sheet is usually pre ground before a final finish can be achieved.
Cold rolled stainless steel has a much smoother surface and is widely used in visually and hygienically critical environments.
Characteristics:
smooth, slightly reflective surface
roughness around Ra 0.3 µm, not guaranteed
suitable for thinner sheets
Even so, cold rolled material is often further ground or polished to achieve a consistent and controlled surface finish.
Surface roughness, also referred to as Ra value, determines how smooth a surface is and how it behaves in use.
A lower roughness results in:
better cleanability
less adhesion of dirt and bacteria
more consistent product quality
Typical guidelines in practice:
food industry: Ra ≤ 0.8 µm
pharmaceutical industry: Ra ≤ 0.4 µm
Because standard stainless steel sheets do not always meet these requirements, grinding to a specified Ra value is often applied. The surface is then fully processed and measured to ensure compliance.
The required finish determines how a stainless steel sheet is processed. This is usually done in multiple steps, using different abrasive grain sizes.
When grinding:
a lower grit, such as K80, results in a coarse surface
a higher grit, such as K320 or higher, results in a finer surface
A commonly used reference:
K320 corresponds approximately to Ra 0.8 µm, provided the process is properly built up
Hot rolled material requires more processing steps than cold rolled material, which directly affects costs.
Depending on the application, a specific finish is selected:
ground stainless steel, technically and visually controlled finish
non directional finish, less sensitive to scratches and widely used in architecture
brushed stainless steel, matte appearance and practical in use
high gloss polished, reflective surface
mirror 8K finish, mirror like quality for high end applications
The right finish is always a balance between functionality, appearance and cost.
A stainless steel sheet is often the starting point for a larger process. The surface condition determines how well subsequent processes perform.
Think of:
electropolishing
pickling and passivation
alternatives to wet blasting, such as ViwateQ® Finishing
Especially in stainless steel surface treatment, a consistent base is essential. Any irregularities in the surface will be directly visible in the final result.
Selecting the right stainless steel sheet comes down to three interconnected factors:
the correct material grade, such as 304, 316 or duplex
the right base material condition, hot rolled or cold rolled
the required final finish and Ra value
Together, these determine:
the required processing steps
the final quality
the total cost
At Van Geenen, we look beyond just the sheet. We focus on the complete process, from base material to final finish.
This includes:
mechanical or manual grinding and polishing
stainless steel surface treatment
alternatives to wet blasting such as ViwateQ® Finishing
This ensures that a stainless steel sheet not only meets specifications, but also performs as intended in practice.
Van Geenen is happy to think along with you about the right stainless steel sheet for your application. Feel free to contact one of our specialists.
