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Categorization and Properties of SAE Cold Rolled Strip Steels (J2392:2024)
SAE J2392 has been reaffirmed in 2024 to define tolerances and attributes of cold rolled strip steels. This recommended practice helps engineers understand the nuances between cold rolled strip and sheet, enabling precise material selection for automotive and other applications. Cold rolled strip steels are produced to tighter dimensional tolerances and are available in a variety of tempers, finishes, and edge conditions.
Cold Rolled Strip vs. Cold Rolled Sheet
The dimensional limits for cold rolled strip are widths from 12.5 mm to 600 mm and thicknesses up to 7.6 mm. Products wider than 600 mm are classified as sheet. Strip thickness tolerances are 58% to 83% of the corresponding sheet tolerances, offering superior precision for critical components.
🛠️ Key Insight: Cold rolled strip steels provide significantly tighter dimensional control compared to sheet, making them the preferred choice for applications requiring close tolerances, such as automotive brackets, clips, and precision stampings.
Temper Designations and Formability
Low carbon cold rolled strip is specified to standard tempers that indicate hardness and formability. As the temper number increases, the steel becomes softer and more ductile. The table below summarizes the five standard tempers.
| Temper Number | Temper Name | Hardness Range | Approx. Tensile Strength (MPa) | Typical Application |
|---|---|---|---|---|
| 1 | Hard | B84 minimum | 620 ± 70 | Flat parts requiring springiness; no cold forming |
| 2 | Half Hard | B70 – B85 | 450 ± 70 | Limited bending (90° across rolling direction, radius = thickness) |
| 3 | Quarter Hard | B60 – B75 | 380 ± 70 | Moderate bending, forming, drawing; 180° bend across rolling direction |
| 4 | Skin Rolled | Up to B65 | 330 ± 40 | Deep drawing; can be bent flat upon itself |
| 5 | Dead Soft | Up to B55 | 300 ± 40 | Deep drawing where stretcher strains acceptable |
Engineering Design Insight: Selecting the correct temper is critical. Harder tempers (1, 2) are suitable for spring clips and elastic parts, while softer tempers (4, 5) provide excellent formability for complex deep-drawn components. Always consider the required bend radius and forming method when specifying temper.
Thickness Tolerances and Edge Conditions
Standard thickness tolerances vary by nominal thickness and strip width. Non-standard tolerances, either tighter or wider, can be negotiated with the strip producer. Edge conditions are specified by number (No.1 through No.6 and skived edges). No.1 edge is suitable for electroplating, while No.3 (squared edge, burr not removed) is most common.
| Nominal Thickness (mm) | Width 12.5 to <300 mm | Width 300 to <450 mm | Width 450 to 600 mm |
|---|---|---|---|
| 4.00 – 6.39 | 0.065 | 0.080 | 0.090 |
| 1.80 – 3.19 | 0.045 | 0.055 | 0.070 |
| 0.75 – 0.99 | 0.030 | 0.040 | 0.050 |
| 0.25 – 0.37 | 0.013 | 0.020 | 0.025 |
⚠️ Common Mistake: Assuming thickness tolerances are uniform across all widths. Always refer to the standard tables and verify with your supplier when tight tolerances are required.
Frequently Asked Questions
What is the maximum width for cold rolled strip steels?
According to SAE J2392, cold rolled strip steels are available in widths from 12.5 mm to 600 mm. Products with widths greater than 600 mm are technically classified as sheet.
What does temper number 5 (Dead Soft) mean?
Dead Soft temper provides maximum softness and ductility, with a tensile strength of about 300 ± 40 MPa. It is used for severe deep drawing applications where stretcher straining is not objectionable.
Can I obtain tighter thickness tolerances than the standard values?
Yes, non-standard tolerances (both tighter and wider) can be specified by agreement between the user and the strip producer, subject to manufacturing capabilities.
Which edge condition is recommended for electroplating?
No.1 Edge (prepared contour) is recommended for applications requiring accurate width or a surface suitable for electroplating, or both.
