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Description
About stainless steel 303:
This is a free-machining wear-resisting stainless austenite steel. To improve its properties, less than 0.60% molybdenum can be added in stainless steel 303 for ablation resistance. After annealing and destressing, Stainless steel 303 has the following mechanical properties: tensile strength 515MPa, yield strength 205MPa, and ductility 40%. Stainless Steel 303 has the standard hardness of HRB 90-100 and HRC 20-25 (note: HRB100 = HRC22.9). With the contents of sulfur and selenium, stainless steel 303 is mainly used in the occasions requiring high machinability and high surface finish. Because of its improved machinability and high temperature adhesion property, the 303 stainless steel is most suitable for automatic lathes, bolts and nuts.
Pitting corrosion of the stainless steel: reason:
Pitting corrosion of the stainless steel often occurs in an aqueous solution environment with iodine, chlorine or bromine. It occurs because the chloridion is an active negative ion which is easy to adsorb and then shoves off the oxygen atom and reacts with the positive ion in the passivation coating to produce a soluble chloride. This soluble chloride damages the passivation coating, forms pores, and produces the phase of pitting corrosion inducement, in which lock-out circuits occur and lead to galvanic corrosion.
Precautionary Measures
1.Choose an appropriate stainless steel for the known environment with possible pitting corrosion. According to experiment results, the stainless steel with a higher content of molybdenum (Mo) or manganese (Mn) has better pitting corrosion resistance.
2.Control the PH value, chloride concentration and temperature of the liquid in contact with the stainless steel.
3.Carry out cathodic protection, anodic protection or both at the same time.
4.Try to use the stainless steel with higher quality, such as 316 or 316L, which has better pitting corrosion resistance.
Differences Between Stainless Steel 303
The 303 stainless steel is a sulfurated free-cutting steel which is mainly used in the occasions requiring high machinability and high surface finish. As a general-purpose stainless steel, the 304 stainless steel is widely used to manufacture the equipment and parts with good comprehensive performance requirements. The chemical composition (%) of stainless steel 303 is C :≤0.15 Si :≤1.00 Mn :≤2.00 P :≤0.20 S :≥0.15 Cr :17.00-19.00 Ni :8.00-10.00. With the contents of sulfur and selenium, stainless steel 303 is mainly used in the occasions requiring high machinability and high surface finish. The 303 stainless steel has improved machinability and high temperature adhesion property, and it is a free-machining wear-resisting stainless austenite steel. To improve its properties, less than 0.60% molybdenum can be added in stainless steel 303 for ablation resistance. It also features good machinability, burning resistance and ablative resistance. After annealing and destressing, Stainless steel 303 has the following mechanical properties: tensile strength σb (MPa)≥520, offset yield strength σ0.2(MPa)≥205, elongation δ5 (％)≥40, fracture surface reduction percentage ψ (％)≥50, hardness: ≤187HB; ≤90HRB; ≤200HV. 304 stainless steel grade: 0Cr18Ni9 (0Cr19Ni9) and chemical component (%): C: ≤0.07, Si: ≤1.0, Mn: ≤2.0, Cr: 17.0-19.0, Ni: 8.0-11.0, S: ≤0.03, P: ≤0.035. The 304 stainless steel is a general purpose stainless steel material with better rust-proof properties than the 200 series stainless steels. It also has excellent resistance against high temperatures up to 1,000-1,200 degrees. The 304 stainless steel has excellent rust and corrosion resistance and good intergranular corrosion resistance. Experiments shows that the 304 stainless steel presents high corrosion resistance in the nitric acid with a concentration ≤65% and below the boiling temperature. It also has good corrosion resistance against aqueous alkalies and most organic acid and mineral acids. 304(0Cr18Ni9) material: As a steel with wide applications, it features good corrosion resistance, thermal resistance, low-temperature strength and mechanical properties. It has good thermal machinability including stamping and bending, without hardening (non-magnetism, service temperature: -196℃～800℃). Purpose: household effects (types 1 and 2 tableware, cabinets, indoor pipes, water heaters, boilers, and bathtubs), auto parts (windshield wipers, silencers and moulded goods), medical apparatuses, construction materials, chemistry, food industry, agriculture and ship components.
To sum up, the 303 stainless steel and the 304 stainless steel have the following main differences:：
1.Because of its free-cutting property, the 303 stainless steel is mainly used in the occasions requiring high machinability and high surface finish. As a general-purpose stainless steel, the 304 stainless steel is widely used to manufacture the equipment and parts with good comprehensive performance requirements (corrosion resistance and formability).
2.They have obviously different contents of sulphur for chemical composition. It is S≤0.030 for the 304 stainless steel and S≥0.15 for the 304 stainless steel.
3.For chemical composition, the 304 stainless steel has no content of selenium, while the 303 stainless steel does.
4.For chemical composition, it is C≤0.15 for the 303 stainless steel and C≤0.08 for the 304 stainless steel.
5.The tensile strength is σb (MPa)≥520 for the 304 stainless steel and σb (MPa)≥515 for the 303 stainless steel.
Application Scope and Purposes of Custom Slotted Round Head Bolts Made of Stainless Steel 303
Main Purpose: environmental protection equipment, medical devices, communication equipment, electric power facilities, electronic products, instruments and apparatus, food machinery, petrochemical industry, shipfitting, pumps, valves&pipelines, curtain walls, outdoor occasions, sports facilities, and exterior trims. Just as the name implies, stainless steel screws are definitely made of stainless steel screw wires by heading and then threading, and have a lot of stainless steel related properties. Considering its properties and organization and other aspects, it is clear that the stainless steel features good mechanical properties like rust resistance, corrosion resistance and high temperature resistance. Of course stainless steel screws have these good mechanical properties too. As the stainless steel is getting better and better, Yijin Hardware can manufacture stainless steel screws in the screw industry with better and better mechanical properties, so that they have higher and higher rust resistance, corrosion resistance and high temperature&pressure resistance. With its unique experience and technologies in terms of custom stainless steel bolts, Yijin Hardware has become a custom stainless steel round head bolt factory trusted and supported by most of partners all over the world!