What is Stainless Flange Bolt
Stainless Flange Bolt
Stainless flange bolt is a type of flange bolt made of stainless steel materials, such as 301、304、302HQ、304M、304HC、304L, etc. Din6921 is a common standard for flange bolt and screws, which is also available for stainelss flange bolt.
Flange bolts are a type of fastener consisting primarily of a hexagonal head, a flange (a washer beneath the hexagon that is fixed together with the hexagon), and a screw (a cylindrical body with external threads), which need to be paired with nuts for fastening and connecting two parts with through-holes. This type of connection is called bolted connection. Removing the nut from the bolt allows these 2 parts to separate, making bolted connections detachable.
Stainless Steel Types for Flange Bolt
| Stainless Steel Types | Stainless Bolt Steel Grade |
|---|---|
| Austenitic | 301、304、302HQ、304M、304HC、304L、321、310、317、347 |
| 316、316L、316TI、304CU等 | |
| Martensitic | 403、410、42 0、440 |
| Ferritic | 430、 405、 409、 434、 444 |
| Duplex | 2205、 2520、 904L |
| Precipitation-Hardening | 630、 631、 632、 660、 660A |
| Heat-resistant chromium alloy | 501、 502、 503、 504 |
| Hastelloy | 501、 502、 503、 504 |
| Super stainless steel | 1.4529 |
Stainless Flange Bolt Application:
Stainless flange bolts are a common type of fastener widely used in highway and railway bridges, as well as in heavy machinery such as industrial and civil construction, cranes, excavators, and other heavy equipment, with a very broad range of applications.
Other Materials for Flange Screws
- High carbon steel with carbon content greater than 0.45%. Currently, hexagonal flange screws made from this material are rarely used in the market.
- Medium carbon steel with a carbon content of 0.25%, commonly referred to domestically as 35 or 45 steel, and internationally as 1035, CH38F, 1039, 40ACR, etc. This material is mainly used for grade 8 nuts, grade 8.8 bolts, and grade 8.8 internal hexagonal products.
- Low carbon steel with a carbon content of ≤0.25%, commonly referred to domestically as A3 steel, and internationally as 1008, 1015, 1018, 1022, etc. This material is mainly used for grade 4.8 bolts, grade 4 nuts, small screws, and other products with no hardness requirements. (Note: Drill tail nails are mainly made of 1022 material.)
- Alloy steel: Alloy elements are added to ordinary carbon steel to enhance some special properties of the steel, such as 35, 40 chromium molybdenum, SCM435, 10B38. Hexagonal flange screws are mainly made of SCM435 chromium molybdenum alloy steel, with main components including C, Si, Mn, P, S, Cr, Mo.
Choose Stainless Flange Bolt from AGICO
The raw materials are sourced from well-known steel mills such as Baoshan Iron and Steel, Dalian Iron and Steel, Taiyuan Iron and Steel, or imported high-quality stainless steel materials such as SUS302, SUS304, SUS316, 316L duplex steel, titanium steel, etc.,
Processed through cold rolling or hot processing, possessing characteristics of high strength, corrosion resistance, high temperature resistance, and durability.
Why Use Stainless Flange Bolts
Among the various equipment on-site, corrosion of flange connection bolts is often overlooked but can have significant impacts and hazards. In the pulping section, flange discs are widely used, and flange bolts are numerous. However, despite being crucial connecting components, flange bolts are often neglected.
To enhance the protection of bolts in daily work, maintenance personnel often use various methods such as machine oil, grease, mixed oil of machine oil and grease, bolt protective caps, etc. (see figure one). Due to the inconvenient maintenance positions of bolt installations, significant inconvenience and safety hazards exist in daily maintenance work. Stainless flange bolt offers excellent anti-corrosion feature in the long service of the equipment.
How Flange Bolt Corrosion Occurs
The bolt heads exposed outside the flange discs are generally in good condition due to ease of maintenance. However, the threaded rod portion passing between two flange discs is not easily protected due to its narrow and inaccessible location, and it is difficult to inspect. Consequently, a considerable portion of bolts exhibits varying degrees of corrosion in the middle section. Particularly for flange discs placed horizontally, some connection bolts show severe corrosion in the middle section. As stress-bearing connecting components of pipelines, they are particularly prone to stress corrosion.
Once corrosion starts, the corrosion rate accelerates progressively. Generally, bolts in the same flange disc exhibit similar corrosion degrees under the same corrosion environment and conditions. When a bolt with severe corrosion and insufficient strength to bear the tension load breaks, the load originally borne by that bolt is instantly transferred to other bolts in the same flange disc, easily causing a chain reaction of bolt fractures with similar corrosion degrees, leading to a massive leakage of internal medium in the pipeline. Therefore, it is necessary to implement a system of annual and location-specific inspections and planned replacement of severely corroded connection bolts in each section. Workshops should be instructed to strengthen inspections in this area to promptly identify and replace severely corroded bolts.
