Why 316 Stainless Steel Bolts Are More Expensive Than 304 — A Technical Insight from ASM FASTENER

2025-10-30 14:32:04

In the fastener industry, stainless steel grades 304 and 316 are among the most widely used materials. However, many customers often ask: why is a 316 stainless steel bolt significantly more expensive than a 304 one, even though they look almost the same? ASM FASTENER explains this from the perspective of material composition, performance, cost, and application.

1. Material Composition Difference — The Key Role of Molybdenum (Mo)

304 Stainless Steel: The basic composition is 18% Chromium (Cr) and 8% Nickel (Ni). It is a general-purpose austenitic stainless steel with relatively low cost.

316 Stainless Steel: Built upon 304, 316 contains an additional 2–3% Molybdenum (Mo) and slightly higher Nickel content (10–14%). Molybdenum is a rare and expensive metal (average global price around USD 45,000/ton), which directly increases raw material cost.

Key Impact: The addition of Mo greatly enhances corrosion resistance, especially in chloride environments such as seawater and acidic media. However, it raises the raw material cost by about 20–30%.

2. Superior Performance — 316 Offers Reliability in Harsh Environments

304: Suitable for general conditions like freshwater and weak acids. However, it tends to rust in high-salt, strong acid, or chloride environments such as marine and chemical industries.

316: The molybdenum addition helps form a more stable passive film, improving resistance to pitting and crevice corrosion by over 30%. It is widely used in marine engineering, chemical plants, and medical devices.

Mechanically, 316’s strengthening effect from Mo gives it higher tensile strength and hardness, making it ideal for high-load or vibration-prone applications. It also maintains better oxidation stability at temperatures above 80°C compared to 304.

3. Price Gap — Combined Effect of Material and Processing Costs

• Raw Material: 304 stainless steel sheets cost about RMB 15,000–20,000/ton, while 316 ranges from RMB 21,000–26,000/ton, a 30–40% difference.

• Molybdenum Contribution: Mo accounts for 15–20% of 316’s total cost and fluctuates widely (Mo prices rose over 50% in 2023).

• Processing Difficulty: 316’s higher hardness increases tool wear during machining and threading, reducing production efficiency by about 10–15%.

4. Application and Market Demand

304 Bolts: Common in construction, household, and general equipment, where corrosion exposure is minimal. High demand and standardization help reduce unit cost.

316 Bolts: Designed for high-corrosion and high-reliability environments such as ships, chemical pipelines, and medical instruments. They often require stricter certifications (e.g., ISO 3506) and offer higher added value.

Example: In seawater desalination plants, 304 bolts may rust within months, while 316 bolts can last for years, significantly lowering maintenance costs.

5. Purchasing Recommendation — Choose Wisely to Avoid Waste

• Choose 304: For indoor structures, furniture, or non-acidic environments, 304 offers excellent cost performance.

• Choose 316: For exposure to saltwater, acids, or alkalis (e.g., food processing equipment, coastal installations), or high-temperature and high-pressure systems such as boilers and energy facilities.

Note: Some low-cost suppliers may mislabel 304 as 316. Always request a material test certificate (e.g., SUS316 mark) or third-party inspection report to ensure authenticity.

Conclusion:
The price difference between 304 and 316 stainless steel bolts is not arbitrary—it reflects the added value of molybdenum-enhanced corrosion resistance, durability, and reliability. At ASM FASTENER, we specialize in producing high-quality stainless steel fasteners, including stud bolts, bolts, and nuts made from ASTM A193/A320 Grade B8, B8M, and other materials, ensuring optimal performance for marine, petrochemical, and offshore engineering applications.