High Strength Steel Applications and Types

Ⅰ. HIGH TENSILE STEEL USES

High tensile strength steel is mainly used for structural applications and can be produced with or without the addition of small amounts of microalloying elements. Under N and N+T heat treatment conditions, higher comprehensive mechanical properties are obtained.

Typical High Strength Steel Applications Include:

• Car body structure

• Large ships and bridges

• Power station equipment

• Boiler pressure vessel

• Lifting equipment

• Mining machine

High Strength Steel Example

For example, Q460 is a type of HSLA steel with higher comprehensive mechanical properties under N, N+T, QT conditions compared with mild steel, in which aluminum is added for deoxidation. The quality grades Q460C, Q460D, and Q460E increase the toughness of steel, making it suitable for various large-scale engineering structures and light structures that require high strength and large loads.

Ⅱ. TYPES OF STEEL USED IN AUTOMOTIVE INDUSTRY

a. High Strength Interstitial-free Steels (IF steels)

High-strength IF steels belong to the product family of conventional high-strength steels by adding different kinds of solid-solution-strengthening alloys such as P, Mn, Si, and proper rolling process control. The high-strength interstitial free steel properties feature the best formability and stamping performance of conventional high-strength steels, making it very suitable for complex-shaped automotive steel parts that have high requirements for deep drawing suitability and strength.

b. High Strength Bake-hardening Steels (BH Steels)

Bake Hardenable (BH) steel grades are conventional high-strength steels with baking hardening effects, suitable for car exposed panels. BH steels exhibit an increase in yield strength after room-temperature stamping followed by bake hardening processing through a thermal cycle comparable to the time-temperature profile used in paint baking, which is commonly seen in automotive painting processes.

c. Phosphorus-Containing Steel

Phosphorus-containing steel uses the solid solution strengthening element phosphorus to increase the strength of the steel plate so that it can be applied to some automobile stamping parts with more complicated shapes.

d. Ultra-Low Carbon Phosphorus-Containing Steels

Ultra-low carbon high-strength phosphorous steels are favored for their deep drawability, formability, and toughness. Solid solution strengthening alloys such as P, Mn, and Si ensure their strength.

e. Isotropic Steels ((I-Steels)

Isotropic steels are low-carbon low-alloyed steel, mainly used for automobile outer panels, and have been commercialized in Europe. The steel product categories are divided into cold-rolled steels, electro-galvanized steel, and hot-dip galvanized and hot-dip galvanized alloyed products, which are mainly used in European series models, while Japanese cars are rarely used.

f. High-strength Low Alloy Steels (HSLA Steels)

High strength low alloy steels, commonly known as HSLA steels, are produced by adding a small number of microalloying elements like Cb, Ti, Mo, V, etc., which offer excellent strength and weldability to it. The main mechanisms include grain refinement, precipitation strengthening, solid solution strengthening, and even phase-change strengthening.