Why Are 316 Stainless Steel Bolts More Expensive Than 304?

2025-06-18 16:01:55

1. Material Composition: The Key Factor Is Molybdenum (Mo)

• 304 Stainless Steel consists primarily of 18% Chromium (Cr) and 8% Nickel (Ni), making it a standard austenitic stainless steel with relatively low cost.

• 316 Stainless Steel builds on the 304 composition by adding 2–3% Molybdenum (Mo) and slightly increasing Nickel content (10–14%). Molybdenum is a rare and expensive alloying element, with a global price averaging around USD 45,000 per ton, which significantly increases the raw material cost.

• Key Impact: The addition of molybdenum enhances corrosion resistance, particularly in chloride-rich environments such as seawater or acidic media. However, it also raises the material cost by approximately 20–30%.

2. Performance Advantage: 316 Offers Superior Reliability in Harsh Environments

• 304 performs well in general environments (e.g., freshwater, mild acids), but is prone to corrosion in high-salt, strong acid, or chloride-containing conditions (e.g., marine or chemical settings).

• 316 forms a more stable passive layer due to molybdenum, offering over 30% better resistance to pitting and crevice corrosion. It's widely used in marine engineering, medical devices, and other high-demand applications.

• In terms of mechanical performance, molybdenum strengthens 316, increasing its tensile strength and hardness. This makes it ideal for high-load, high-wear conditions, especially where bolts are subject to vibration or pressure.

• High-temperature stability is also superior; above 80°C, 316 has a slower oxidation rate than 304, contributing to longer service life.

3. Price Difference: Combined Effect of Raw Material and Processing Costs

• Raw material cost: 304 stainless steel typically costs CNY 15,000–20,000/ton, while 316 ranges from CNY 21,000–26,000/ton—a 30–40% price gap.

• Molybdenum accounts for 15–20% of 316's total cost and its price is highly volatile (e.g., molybdenum prices surged over 50% in 2023).

• Processing difficulty: Due to its higher hardness, 316 wears out tools faster during cold working processes like cutting or threading. This lowers production efficiency by about 10–15% and increases manufacturing cost.

4. Applications and Market Demand

• 304 Bolts: Commonly used in construction, furniture, and general equipment exposed to non-corrosive environments. Demand is high and production is standardized, keeping unit costs low.

• 316 Bolts: Designed for corrosive and high-reliability environments such as marine structures, chemical pipelines, and medical equipment. Often require stricter certifications (e.g., ISO 3506), leading to higher added value.

  Example: In seawater desalination plants, bolts made from 304 may corrode within months, while 316 bolts can last for years, significantly reducing maintenance costs.

5. Purchasing Advice: Choose Based on Application to Avoid Overspending

• Choose 304 for: General construction, indoor furniture, and non-acidic environments — offers excellent value for money.

• Choose 316 for: Exposure to saltwater or acidic/alkaline media (e.g., food processing equipment, coastal infrastructure);
  high-temperature or high-pressure environments (e.g., boilers, energy systems).

• Caution: Be aware of counterfeit products — some suppliers may label 304 as 316. Always verify with a material test report (e.g., SUS316 marking) or third-party inspection.