Performance improvement of stainless steel screws

Update:20 Oct 2020
Summary:

The main component of stainless steel screws is stainle […]

The main component of stainless steel screws is stainless steel, so what is stainless steel? What are the main properties of stainless steel? Stainless steel refers to steel that does not rust in weak corrosive media such as air, water, and steam, and is resistant to corrosion in strong corrosive media such as acid, alkali, and salt solution. Some of the steels that do not rust in weakly corrosive media are not necessarily resistant to corrosion in strong corrosive media, while steels that are resistant to corrosion in strong corrosive media generally have good rust resistance.
Stainless steel screw The stainless steel group and performance grade marking system of the nut. The material marking consists of two parts separated by a short stroke. The first part is the group of Peugeot steel, and the second part marks the performance level.
  The group (part one) of steel is marked by a letter and a number. The letter represents the type of steel, and the number represents the range of chemical composition of this type of steel. Among them: A-austenitic steel; C-martensitic steel, F-ferritic steel.
   Performance level (Part 2) mark: For nuts with m>=0.8D (type 1), it is composed of two numbers and represents 1/10 of the guaranteed load stress.
   Example:
  1) A2-70 means: austenitic steel, cold working, minimum guaranteed stress (type 1 nut) is 700N/mm2 (700MPa);
  2) C4-70 means: martensitic steel, quenched and tempered, minimum guaranteed stress (type 1 nut) is 700N/mm2 (700MPa);
  3) A2-035 means: austenitic steel, cold working, minimum guaranteed stress (thin nut) is 350N/mm2 (350MPa).
In order to make stainless steel not only have good corrosion resistance, but also good mechanical and physical properties, according to different requirements, in addition to adding a higher content of alloying element chromium, nickel, molybdenum, manganese, nitrogen, etc. Other alloying elements. In this way, not only can the chemical composition of the passivation film be changed, and its corrosion resistance in harsh media can be strengthened, but the steel can also obtain sufficient strength, plasticity and toughness, as well as good process performance, such as weldability and processing. Sex and so on.


What is the minimum chromium content required for stainless steel? The American and European standards stipulate that it is not less than 10.5% (mass fraction, the same hereinafter), the Japanese Industrial Standards generally stipulate that it is not less than about 11%, and my country generally believes that it is not less than 12%. In fact, the corrosion resistance of stainless steel and the content requirements of chromium element depend on many factors such as the type, concentration, temperature, pressure, flow rate of the corrosive medium, and other alloying elements in steel except chromium.