Stainless steel strips are thin, rolled coils that are widely used in construction, automotive, aerospace, and medical industries. The real success of stainless-steel strips depends not only on the material grade and its heat treatment, but also on its thickness, width, and length tolerances. In this article, we will explore the understanding of thickness, width tolerances, and length tolerances, and how these factors affect the application, standards, quality control, and tips for selecting stainless steel with proper tolerances.
Figure 01: Stainless steel strip
Understanding Thickness in Stainless Steel Strips
Thickness in stainless steel is the measurement of the distance between two flat surfaces. The thickness of Stainless-steel strips generally ranges between 0.4 mm- 6 mm. For example, if a stainless steel strip is ordered at 0.4mm thickness with ±0.02mm tolerance, the actual material can be supplied between 0.38mm and 0.42mm. During the manufacturing, the heat treatment, rolling, and grinding processes affect the thickness of stainless-steel strips. Thin strips are used in the electronic and spring gauge industries, while thick strips are used in construction and the automotive industry.
Width Tolerance of Stainless-Steel Strips
Width Tolerance refers to the permissible variation from the order width. For example, if a material is ordered at 0.5mm width with ±0.01 tolerance, then the actual material can be supplied between 0.49 mm- 0.51mm. The width can be controlled by the Slitting machine, deburring, and trimming processes. Width tolerances are important because they help to minimize waste and maintain product quality in automotive fuel cells, aerospace, and electronic devices.
Length Tolerance of Stainless-Steel Strips
Length tolerance ensures that strips fall within acceptable dimensional limits. It becomes important in frames, layered components, where multiple strips must be aligned perfectly to avoid poor fitting. The precise length tolerance can be achieved by the precision cutting machines, calibration equipment, and proper coil handling. Large tolerance ranges can be acceptable for construction and loading-bearing applications. It is necessary to achieve tighter tolerances in aerospace and in the medical industry to avoid failure and ensure safety. To ensure uniformity across the world, different international standards are used for length tolerances. One of them is ASTM A480/ A480M, which discusses the general requirements for flat-rolled stainless steel.
How Thickness, Width, and Length Tolerances Affect Applications
The little variations in thickness, width, and length tolerances can lead to a reduction in efficiency, an increase in cost, wastage of material and even the failure of the material. When thickness, width, and length tolerances are well controlled, the strips can work smoothly in applications. Table 1 shows the typical tolerance range of thickness, width, and length used in different industries and their effect on the application. Let’s discuss them one by one in detail:
Effect of thickness tolerance:
- Mechanical performance: The thickness tolerance strongly influences the load-bearing, elasticity, and strength. Tight thickness means that strips require consistent performance and durability. For example, if the spring thickness is inconsistent, it leads to inconsistent return from its original position and failure of the material.
- Formability: Controlled thickness tolerance is necessary in bending, stamping, and deep drawing. Variation in tolerance leads to deformation, cracking, and material defects. During the stamping process, if the clearance gap (the distance between the punch and die) is small and the strip thickness exceeds the specified value, the tool may be damaged or fail.
- Coatings: Uniform thickness of coating may lead to better adhesion of coating with substrate as compared to non-uniform thickness coating.
Effect of width tolerance:
- Edge Quality and Safety: If there is poor control of width tolerance in cutting, this may produce uneven and poor surface finishing of stainless-steel strips.
- Aerospace industry: The turbine shims and precision parts demand extremely tight width tolerances to avoid defects and performance.
- Medical industry: During the manufacturing of surgical tools, it is necessary to maintain a tight width tolerance.
- Construction: In cladding and roofing, slightly larger material than specified can be acceptable.
Effect of length tolerance:
- Dimension Accuracy: Controlled length ensures that strips meet the exact specifications for welding and blanking. If strips are cut longer than their required length, it may require the cutting and slow down the production process.
- Electronic: It is necessary to achieve a tight length tolerance for components like connectors, shielding strips to get better performance.
- Process Reliability: Length tolerance maintains consistency during the manufacturing of items. In stamping presses, an over-length strip can jam the die.
- Cost Efficiency: Overlength strips than specification require the cutting process. Cost can be increased if a strip of stainless steel is manufactured 0.2mm extra than its requirement.
Standards and Specifications
The international standards like ASTM, EN, JIS, and DIN help to define the tolerance ranges according to the thickness of the material. These standards help both suppliers and customers to ensure standardized stainless-steel strips. The following table shows the tolerances of width, length, and thickness according to different standards:
Table 1: Width, length, and thickness tolerances of stainless-steel strips according to different standards
Parameter | Nominal Size | Typical Tolerance Range | Standard Reference |
Thickness | 0.30 mm | ±0.03 mm | ASTM A480 (Cold-rolled) |
1.00 mm | ±0.05 mm | ASTM A480 | |
3.00 mm | ±0.15 mm | ASTM A480 | |
Width | ≤ 1000 mm | ±1.0 mm | ASTM A480 |
> 1000 mm | ±1.5 mm | ASTM A480 | |
Precision Strip | ±0.2 mm | JIS G4305 | |
Length | ≤ 3048 mm | ±2.0 mm | ASTM A480 |
> 3048 mm | ±3.0 mm | ASTM A480 |
Quality Control and Measurement Methods
There are many methods used to ensure quality control and measurement of thickness, length, and width according to standards. Micrometers and digital calipers are used to control the thickness of material. The width of the material can be controlled by using the laser gauge and edge detectors. Length can be controlled by using the automated length sensors and calibrated shearing equipment.
Tips for Selecting Stainless Steel Strips with Proper Tolerances
The following are the tips to ensure the stainless-steel strips with proper tolerances:
- Select the thickness, width, and length of strips according to the application.
- Check the tolerance of width, thickness and length of strips mentioned in ASTM, EN, and JIS standards.
- Check the suppliers who are selling at a low price with the required tolerances.
- Ensure tolerance during the manufacturing processes, such as stamping and bending.
- Verify the measurement with different tools to measure the thickness, length and width of strips.
Conclusion
The performance of stainless-steel strips depends not only on the material grade, but precise tolerances of thickness, width and length are also important. Different international standards and advanced measurement tools are used to ensure the tolerances of thickness, width and length. By matching the tolerances according to application, industries can achieve excellent performance, cost efficiency and durability of stainless-steel strips.
