1、 Chemical composition
1) Chemical composition
Carbon: The main component that constitutes the strength of steel. If the carbon content increases, the strength of the steel will improve, but the plasticity, durability, cold bending function, weldability, and rust resistance of the steel will decrease, especially the impact resistance at low temperatures. Manganese and silicon: favorable elements in steel are Oxygen scavenger, which can improve strength without too much decrease in plasticity and impact resistance. Vanadium, niobium, titanium: Alloy elements in steel that can improve steel strength while maintaining outstanding plasticity and durability. Aluminum: strong Oxygen scavenger, which can further reduce harmful oxides in steel by compensating deoxidization with aluminum. Chromium and nickel: alloying elements that improve the strength of steel. Sulfur and phosphorus: Impurities and harmful elements left in steel during the exercise process. They reduce the plasticity, durability, weldability, and fatigue strength of steel. Sulfur can make steel “hot brittle”, while phosphorus can make steel “cold brittle”. “Hot brittleness”: sulfur can generate Iron(III) sulfide that is easy to melt. When Hot working and welding make the temperature reach 800~1000 ℃, the steel will appear crack and brittle. Cold brittleness “: The appearance of phosphorus causing a significant decrease in the impact resistance of steel at low temperatures. Oxygen and nitrogen: Harmful impurities in steel. Oxygen can make steel hot brittle, while nitrogen can make steel cold brittle.
2、 The impact of financial shortcomings
Common metallurgical drawbacks include segregation, non-metallic doping, porosity, cracks, delamination, etc., all of which can lead to poor functionality of the steel.
3、 Steel hardening
Cold working, such as cold drawing, cold bending, punching, and mechanical shearing, causes significant plastic deformation of steel, which then advances the yielding point of the steel and together reduces its plasticity and resistance. This appearance is called cold work hardening or strain hardening.
4、 Temperature effect
Steel is moderately sensitive to temperature, and both rising and falling temperatures cause changes in the functionality of the steel. In contrast, the low-temperature function of steel is more important.
On a positive temperature scale, the overall trend is that as the temperature increases, the strength of the steel decreases and the deformation increases. Within about 200 ℃, there is no significant change in the functionality of the steel, while between 430 and 540 ℃, the strength (yield strength and tensile strength) sharply decreases; At 600 ℃, the strength is very low and cannot withstand the load. In addition, there is a blue brittle appearance near 250 ℃, and a creep appearance around 260-320 ℃.
