Steel pipes have various use in marine projects, from offshore oil drilling to rig construction. Among these, austenitic steel pipes are preferred, especially in applications like boating, where these pipes get constantly exposed to the elements. This piping is highly corrosion resistant and sturdy, making them a perfect fit to weather the harsh salt water.
In shipping operations, austenitic steel pipes have applications like
- Onboarding plumbing requirements
- Saltwater piping
- gray/black water piping
- vent/rain piping
- Deck fixtures
Relevant Specification for Boat Piping: ASTM A312 S31254 Austenitic Steel Pipe
Characteristic Features of ASTM A312 Austenitic Steel Pipe Specification
- ASTM A312 specifications cover the production standards of heavily cold worked, seamless, and welded stainless steel pipes.
- These stainless steel pipes' typical diameter varies from ⅛ inches to 30 inches.
- The specification covers pipe schedules SCH S10 to SCH S80.
- The customer and producer must discuss the analysis method for nitrogen content in ASTM A312 pipes.
- During production, ASTM A312 pipes shall be exposed to a maximum heat of 1900 Degrees Fahrenheit.
- After hot rolling, stainless steel pipes under this specification should be cooled immediately via water immersion or a similar fast-cooling method.
Types of Stainless Steel Used in Boats
Stainless steel pipes in boats and other marine applications are chosen based on their ability to withstand service environments. These pipes must maintain their structural integrity by exhibiting their resistance to corrosion. Stainless steel products are preferred over other steel types owing to reliable tensile properties and easy fabrication.
Among stainless steels, austenitic and super austenitic steels containing over 6% Molybdenum are more frequently used for purposes that require frequent contact with seawater. These pipes can get further divided into subcategories like
- Austenitic stainless steel pipes and their derivates may be suitable for applications requiring intermittent seawater contact or splash zone uses.
- Super austenitic stainless steel pipes can get used for applications requiring permanent seawater immersion due to their high Moly content.
- Super duplex stainless steel pipes have applications in projects requiring direct and long contact with saltwater.
- Duplex stainless steel pipes can get used in places with lower chloride content.
Depending on their corrosion resistance, austenitic and super austenitic stainless steel pipes have various boating applications. These uses have been summarized in the following chart.
| Stainless Steel Type | Relevant Specifications | Uses/Applications in Boats |
| Austenitic Stainless Steel | EN10088 | Austenitic stainless steel pipes under EN 10088 specifications are typically used as propeller shafts for boats. |
| Austenitic Stainless Steel | AISI 316AISI 316 L | Austenitic stainless steel pipes under specifications AISI 316 and AISI 316 L have numerous applications, including· Deck components for boats· Brackets for boats |
| Super Austenitic Stainless Steel(Containing more than 6% Moly) | ASTM A312 S31254 | ASTM A312 S31254 super austenitic stainless steel pipes are used for purposes including· Boat hull attachments· Ship grills· Heat exchangers for boats |
| Super Austenitic Stainless Steel(Containing more than 6% Moly) | ASTM A321 S31254 | Super austenitic stainless steel pipes under specification ASTM A312 S31254 are used for various purposes in boats. Due to their high molybdenum content, they are very resistant to corrosion. This property makes these pipes perfect for applications requiring prolonged moisture contact.As a result, these super austenitic pipes are used in· Pumps for boats· Boat winches· Plumbing for storage vessels. |
ASTM A321 S31254
Super austenitic stainless steel pipes under specification ASTM A312 S31254 are used for various purposes in boats. Due to their high molybdenum content, they are very resistant to corrosion. This property makes these pipes perfect for applications requiring prolonged moisture contact.
As a result, these super austenitic pipes are used in
- · Pumps for boats
- · Boat winches
- · Plumbing for storage vessels.
Required Tests for ASTM A312 S31254 Stainless Steel Pipes
ASTM A312 stainless steel pipes must pass numerous tests before they can be considered ready for service. Manufacturers conduct the following analysis to test their mechanical endurance and tensile capabilities.
Transverse or Longitudinal Tension Test
This test is conducted to test the pipe tension. Out of 100 pipes, two random piping get chosen to run the mechanical analysis on.
Flattening Test
This analysis is intended for material heat treated in a continuous furnace with automatically controlled heat pyrometers up to 50 Degrees Fahrenheit. For batches treated with furnaces not equipped with recording pyrometers controlled within this temperature range, flattening tests can be conducted on each heat-treated lot amounting to 5%. For this test, 5% of every batch with a minim of 2 pipe lengths is chosen.
Grain Size Determination
The grain size of stainless steel pipes under specification ASTM 312 shall be determined on each heat treatment lot formed in a batch-type furnace with recording pyrometers within 50 Degrees Fahrenheit or less. The pipes to be tested will consist of 5% of each batch with a minimum limit of 2 pipe lengths.
Types of Production Required for ASTM A312 S31254 Stainless Steel Pipes
A312 specifications cover seamless, cold/hot worked, and welded steel pipes. The manufacturing process for each of these varies, requiring specific production conditions. Following are the types of production associated with ASTM A312 pipes.
- Seamless Pipe Production
This method involves the production of seamless pipes made from steel ingots and billets. These materials must be hot rolled before passing through cold drawn or cold rolling.
- Electrically Welded Pipe Production
Welded pipes under ASTM A312 specs include those piping that does not require filler metal for welding. Instead, pipes made with automatic fusing processes are preferred due to their high stress and corrosion resistance. ERW pipes fall under this category due to their barely visible seams.
- Cold Worked Pipe Production
Cold working helps improve the strength and toughness of the steel pipe by exposing them to high pressure at room temperature. This process results in pipes that are heavier than hot-rolled pipes.
- Welded /HCW Pipe Production
According to ASTM A312 specs, welded/ HCW pipe with a Nominal Pipe Size of 14 or less should have a single longitudinal weld. A consultation with a client is necessary for welded/HCW pipes with NPS larger than this. After client approval, they can be customized by welding two longitudinal falt stocks or sport a single welded seam.
Chemical Properties of ASTM A312 S31254 Austenitic Steel Pipe
| Chemical Properties | Value |
| Sulfur | 0.01% |
| Silicon | 0.8% |
| Phosphorous | 0.03% |
| Nitrogen | 0.18% to 0.25% |
| Nickel | 17.5% to 18.5% |
| Molybdenum | 6% to 6.5% |
| Manganese | 1% |
| Copper | 0.5% to 1% |
| Chromium | 19.5% to 20.5% |
| Carbon | 0.02% |
Mechanical/ Tensile Properties of ASTM A312 S31254 Austenitic Steel Pipes
| Mechanical Properties | Value |
| Yield Strength | 310 MPa |
| Tensile Strength | 655 MPa to 675 MPa |
| Elongation A50 | 25% to 35% |
| Poisson’s Ratio | 0.3 [-] normal for austenitic pipes |
| Elastic Modulus | 195 GPa normal for austenitic pipes |
| Shear Modulus | 77 GPa normal for austenitic pipes |
Thermal/Electrical Properties of ASTM A312 S31254 Austenitic Steel Pipes
| Thermal/Electrical Properties | Value |
| Melting Point | 2246 Degrees Fahrenheit to 2696 Degrees Fahrenheit |
| Thermal Conductivity | 11W to 21 W (normal for austenitic stainless steel pipes) |
| Specific Heat Capacity | 440J (normal for austenitic stainless steel pipes) |
| Coefficient of Thermal Expansion | 1.7E-5 to 1.9E-51 K (normal for austenitic stainless steel pipes) |
| Electrical Resistance | 8.5E-7 Ω·m (normal for austenitic stainless steel pipes) |