High-strength low-alloy (HSLA) steel does not have one universal set of mechanical properties. Yield strength, tensile range and elongation depend on the exact grade, product form and thickness. The table below compares selected SSAB Strenx 650 and 700 products using SSAB’s published product data. It is a quick comparison reference, not a substitute for the current product certificate or the specification on a purchase order.

Selected HSLA steel mechanical properties

Use the exact grade name and thickness band when reading the values. The Strenx 650MC and 700MC entries are hot-rolled coil, slit-coil or sheet products made for cold forming. Strenx 700 CR is a cold-rolled sheet product. Strenx 700 E and 700 F are plate grades. Their strength ranges are not interchangeable simply because each product belongs to the Strenx 650 or 700 family.

How to read the strength columns

Yield strength marks the stress at which the material begins to deform permanently under the applicable tensile test. Tensile strength is the reported range or maximum stress reached in that test before fracture. Elongation describes extension over a defined gauge length. A80 and A5 use different specimen gauge lengths, so their percentages should not be compared as if they were the same test. The table identifies the test orientation as well: SSAB reports longitudinal mechanical properties for the MC products, while the 700 E/F table is for transverse test pieces.

Thickness matters. Some grades lower the minimum specified yield strength as plate becomes thicker. For Strenx 700 E, for example, the SSAB table changes the minimum from 700 MPa in the thinnest band to 650 MPa above 53 mm. SSAB also notes that the minimum yield value for 650MC and 700MC products thicker than 8 mm may be 20 MPa lower than the nominal band value. We show that lower bound in the table for the affected thickness band so the footnote is not hidden.

Using the data during material selection

Suppose a fabricator is comparing 6 mm Strenx 650MC and 700MC for a cold-formed support. The table can narrow the comparison: both product pages list their grade-specific minimum yield and tensile ranges, while the higher-strength grade has a different elongation minimum. The designer still has to check the part geometry, forming radius, weld detail, local buckling, fatigue, impact requirement, and design code. A higher published yield value alone does not prove that a thinner part will perform safely.

For a plate component, choose the row by both grade and nominal plate thickness. Do not use a sheet or coil value for a plate, or transfer the result to another manufacturer’s S650MC or S700MC material without verifying that product’s exact standard and delivery condition. Grade names that look similar can have different guarantee ranges, test directions, and inspection requirements.

Limits and common mistakes

These figures are minimum or range values published for named SSAB product families. They do not identify the result for an individual heat or certify a delivered piece of steel. Check the current data sheet and material test certificate before acceptance. The table also does not provide fatigue strength, weld-joint strength, design resistance, hardness, or toughness for every grade and thickness. Where impact performance is a design requirement, use the grade-specific impact data and test temperature from the current technical documentation.

Do not equate yield strength with allowable design stress. Apply the governing structural or machine-design standard and its safety factors. Do not extrapolate a row beyond its thickness range, assume the same properties after heating, or rely on a nominal grade label in place of traceable mill documentation. SSAB notes that its cold-forming 650MC and 700MC products can lose guaranteed properties after heat treatment above 580 °C; the 700 E/F products also have their own elevated-temperature limit.

Related engineering references

Browse more mechanical design and manufacturing topics in the Mechanitec Engineering category.

Sources

• SSAB Strenx 650MC D/E product data.
• SSAB Strenx 700MC D/E product data.
• SSAB Strenx 700 CR product data.
• SSAB Strenx 700 E/F plate data.