1. STEEL AS A CONSTRUCTIONAL MATERIAL
Advantages:
Combination of high stiffness (E = 2,1∙105 MPa), static (σT) and syclic (σ-1) strength with sufficiently high structures reliability (δ , KCU) in service
Wide range of mechanical and service characteristics at the expense of change in composition (alloying) and structure (heat treatment and other technologies)
Disadvantages:
Large specific weight, low specific strength σT /γ
Susceptibility to corrosion

2. ALLOYED STEELS Alloying elements:
increase strength properties of steel, but may reduce an impact toughness (> 1 % alloy additives);
elevate the temperatures of phase transformations (critical points of steel);
decrease a critical cooling rate of quenching;
enlarge hardness penetration;
reduce average grain size;
add special service properties (heat resistance, corrosion resistance at al.)

3. Construction low-alloy steels: bridges
GRADES: 15ХСНД, 16Г2АФ (Russian)
high-strength low-alloy (USA)

4. Construction low-alloy steels: beams, building metalworks
GRADES: 09Г2С, 14Г2, 15ГФ, 10ХНДП (Russian)
high-strength low-alloy (USA)

5. Construction low-alloy steels: oil and gas pipelines
GRADES: 17ГС (Russian)
high-strength low-alloy (USA)

6. Construction low-alloy steels: gas and oil storages, welded tanks and capacitances
GRADES: 10Г2С1, 12Г2СМФ (Russian)
high-strength low-alloy (USA)

7. Steels for case hardening: gear wheels
GRADES: 15Х, 20Х, 20ХФ, 12ХН3А, 12Х2Н4А;
18Х2Н4ВА;
18ХГТ, 25ХГТ

8. Steels for heat refining: turbine rotors
GRADES: 40Х, 40ХФА, 40ХН, 40ХН2МА (Russian)