Stainless Sheet Thickness Standards & Selection: GB/T Guide

1. National Standard: Benchmark System for Thickness Specifications

The Chinese stainless steel plate thickness standard system is divided by hot rolling and cold rolling processes. According to the current national standard GB/T 4237-2015, the standard thickness range of hot-rolled stainless steel plates is 3.0mm to 100mm, which is suitable for load-bearing structural parts; while GB/T 3280-2015 stipulates that the thickness range of cold-rolled plates is thinner, from 0.3mm to 4.0mm, and is mainly used in the field of precision machining. This standard system not only clarifies the basic thickness value, but also strictly limits the tolerance control. For example, for a cold-rolled plate with a nominal thickness of 1.5mm, the actual thickness must not be less than 1.38mm when the width is 1000mm, and the minimum allowable value is 1.35mm when the width increases to 1500mm. These tolerance requirements directly reflect the national standard’s control over the homogeneity and reliability of materials.

International comparison shows that the American standard ASTM A240 has more stringent requirements on thickness tolerances. For example, the allowable deviation of 304 stainless steel plates is only ±0.015mm, which is 25% higher than the national standard of ±0.02mm. Enterprises need to pay special attention to this difference in the production of export products.

2. Thickness classification and tolerance control

According to the general industrial classification, stainless steel plates can be divided into three thickness grades:

• Thin plates (0.2-3mm): represented by 0.5mm electronic component housings, suitable for lightweight scenarios
• Medium plates (3-6mm): Commonly used in kitchenware and low-pressure containers
• Thick plates (>6mm): Used for heavy-duty structures such as bridge bearings

Tolerance control level directly reflects manufacturing capabilities. Take the nominal 1.5mm plate as an example:

• The national standard allows a minimum thickness of 1.35mm (when the width is 1500mm)
• The Japanese standard JIS G4305 stipulates that the lower limit of the tolerance under the same width is 1.35mm
• If the actual measured value of the 1.5mm plate with a width of 1800mm is lower than 1.35mm, it is a defective product

The surface treatment process will also affect the measured thickness. For example, mirror polishing will reduce the actual thickness of the 1.5mm plate by about 0.1mm, and processing allowance must be reserved during design.

3. Thickness differentiation selection for industry application scenarios

Architectural decoration field The curtain wall stainless steel panel must meet the JGJ133-2013 specification, which clearly stipulates that the plate thickness should not be less than 2.5mm** to ensure wind pressure resistance. Elevator car decorative panels are not subject to direct impact, so 1.2-2.0mm thin plates can be used to reduce the load.

Chemical equipment field Pressure vessel design needs to add corrosion allowance. According to engineering practice, the calculated thickness of the cylinder should be increased by 1-2mm, and the flange connection should be additionally thickened by 2-3mm to resist stress concentration. For example, chlor-alkali reactors often use 6-8mm thick 316L stainless steel plates, using molybdenum elements to enhance corrosion resistance.

Transportation field The stainless steel plate in the basin support of the railway bridge is used as a sliding subassembly. When the length is ≤1500mm, a 2mm mirror plate is used, and when it is >1500mm, it needs to be increased to 3mm to ensure low friction characteristics under dynamic load. The battery tray of new energy vehicles uses 1.8mm ultra-thin high-strength steel plates, which can achieve a 30% weight reduction without reducing safety through rolling process optimization.

Medical and food fields Surgical instruments use 0.3-0.8mm thin plates to ensure precision, while food cans need to be more than 1.2mm thick to withstand repeated thermal shocks during pasteurization. Parts that come into contact with acidic ingredients (such as kimchi fermentation tanks) should have an additional 0.5mm corrosion allowance.

4. Common misunderstandings in procurement practice

Misunderstanding 1: Nominal thickness is the same as actual thickness

• Case: The actual thickness of the purchased 1.5mm plate is only 1.3mm
• Analysis: It is lower than the minimum limit of 1.35mm in the national standard, which is a material fraud
• Countermeasure: Require suppliers to provide spectral detection report and multi-point thickness measurement (3 points on the edge/middle of the plate)

Misunderstanding 2: Unified thickness is suitable for multiple scenarios

• Case: 2mm plate is used for curtain wall and interior decoration at the same time
• Analysis: Curtain wall needs ≥2.5mm to meet wind pressure resistance, and 1.2mm is enough for interior decoration
• Countermeasure: Differentiate material selection according to JGJ133-2013 specification

Misunderstanding 3: Ignoring the thinning effect of processing

• Case: Laser cutting leads to design size deviation
• Analysis: Heat-affected zone thinning reaches 0.3mm
• Countermeasures: Add 0.1-0.3mm process allowance according to the finished product size

5. Comparison of international standards and key points of compliance

The global mainstream standard system has regional characteristics for thickness regulations:

• China GB: The tolerance of hot-rolled plates is relaxed as the width increases, such as a ±0.26mm deviation is allowed when the width of 4mm plates is 2000mm
• US ASTM: Mandatory requirement for constant tolerance across the entire width range
• EU EN: Additional tolerances are added for special surface-treated plates

Export products need to focus on:

• American standard container plates need to provide ASME certified thickness calculation sheet
• EU pressure equipment must comply with PED 2014/68/EU Directive
• Japanese standard JIS G4305 requires a plate shape inspection report when the width is >1250mm

When referring to international standards, it is recommended to visit the [ISO official website] (https://www.iso.org) to obtain the latest version to avoid adopting abolished standards.

6. Technological innovation and future trends

Rolling technology breakthroughs promote the development of extreme specifications:

• Ultra-thin field: Precision rolling achieves mass production of 0.15mm ultra-thin plates to meet the needs of flexible circuit substrates
• Ultra-thick field: 3800mm wide-width rolling mill put into production, producing 12.9×3796×12010mm LNG pipeline extra-thick plates, breaking the dependence on imports

Lightweight technology becomes a new trend:

• New energy vehicles use 1.8mm high-strength stainless steel to replace traditional 3mm carbon steel, reducing weight by 30%
• Composite structure research and development: such as 0.8mm stainless steel-aluminum honeycomb composite plates for construction, with strength equivalent to 5mm solid plates

Kopsavilkums

The selection of stainless steel plate thickness is a technical decision: it is necessary to comprehensively consider national standards (GB/T 4237, GB/T 3280), application scenario mechanical requirements, processing technology characteristics and international standard differences. Building curtain walls adhere to the 2.5mm bottom line, chemical equipment reserves corrosion margins, and medical equipment accurately controls micron-level thin plates – each scenario has its thickness logic.

Master the key points of tolerance control (such as the actual measurement of 1.5mm cold-rolled plates is not less than 1.35mm), establish a supplier thickness measurement verification mechanism, and pay attention to international standard dynamics, so as to achieve the best balance between safety and economy. With the advancement of rolling technology, new stainless steel plates with ultra-thin and high-strength characteristics will continue to expand their application boundaries.

This article refers to the authoritative release of the National Standards Committee. The latest full text of the standard can be accessed at [National Standard Full Text Public System] (https://openstd.samr.gov.cn) for query.