1.Mild Steel. Mild steels are steels with high ductility and formability, with relatively low yield strength. The different grades are generally a balance between the required formability and strength. Interstitial free (IF) grades are typically silicon killed steels and non-IF grades are typically aluminum killed steels. The higher formability grades are typically stabilized by titanium, niobium and/or boron in lieu of carbon or nitrogen.

2. High Strength Low Alloy (LA). Steels usually have higher strengths through the addition of micro-alloying additions such as vanadium, niobium, titanium, molybdenum, etc. Also known as HSLA. High strength low alloy steels with sulphide control to improve edge
stretching and bendingare designated as LAS. Furthermore, certain alloy steels (particularly those with higher strength) exhibit larger anisotropy in properties depending on the manufacturing process. High strength alloy steels that exhibit larger anisotropy are designated as LA/AI.

3. Carbon Manganese (CMn). Carbon Manganese steels are an intermediate grade between high strength low alloy and dual phase, which exhibit more strain hardening behavior than low alloy steels.

4. Bake Hardening (BH). Bake hardening steels exhibit a marked increase in yield strength when processed through the paint bake process (elevated temperature). The time temperature
dependence of the strengthening mechanism can limit storage and shipping.

5.Dual Phase (DP). Dual phase steels exhibit a microstructure consisting of martensitic regions in a ferritic matrix. They tend to exhibit a strong work hardening tendency and are often suitable for
forming operations with significant stretching.

6. Transformation Induced Plasticity (TR). These steels have a typically ferritic / bainitic microstructure plus some retained austenite. During processing the metastable retained austenite transforms to martensite, leading to a significant work hardening. Tempering is usually done following transformation. Also known as TRIP.

7. Complex Phase (CP). These steels consist of fine grained multiple phase microstructures, typically a mixture of hard phases such as martensite or bainite in a ductile ferritic matrix. (These steels tend to have a lower hardening coefficient than dual phase steels).

8. Martensitic (MS). The microstructure of these steels is predominately martensite giving them a high strength and lower ductility than most other grades.

9. Ferritic Bainitic (FB) steels have a microstructure of bainite in a ferritic matrix. The ferritic matrix is typically strengthened through precipitation, grain refinement, and high dislocation density.

10. Future Grades. The following grades are not currently called out as part of this specification, but are included for completeness as they may be required in future revisions and for reference against similar industry specifications.

11. (High strength) Interstitial Free (IF) steels typically achieve their strengths through solid solution strengthening with manganese, silicon and phosphorous. They typically exhibit a pronounced yield point, high ductility and r-values, and storage times do not tend to affect their
high formability.

12. Small Grain Size Low-Alloy (MC) micro-alloyed steels achieve a fine grained microstructure through thermo-mechanical processing using finely dispersed precipitates to inhibit grain growth (typically carbides and nitrides).

13. Twinning Induced Plasticity (TWIP). These are austenitic steels with a high manganese content. During deformation the austenite undergoes twinning which causes a high hardening rate (n-value) as the microstructure becomes finer. The resultant twin boundaries act like grain boundaries and strengthen the steel. Also known as TWIP.