Introduce the Difference between ASTM A333 and ASTM A334

ASTM A333 for Seamless and Welded Steel Pipe for Low-Temperature Service

ASTM A334 for Seamless and Welded Carbon and Alloy Steel Tubes for Low-Temperature Service

Fundamentally, both ASTM A333 and A334 are designed for low-temperature applications. However, they differ significantly in their intended uses.

A333 is primarily designed for low-temperature pressure vessel piping systems and fluid transportation pipelines, while A334 is tailored for low-temperature heat exchanger tubes, clearly distinguishing the functional requirements between transport pipes and heat exchanger tubes. In practical engineering, this distinction reduces the risk of selection errors—A333 pipes ensure transport safety, while A334 tubes optimize heat exchange efficiency.

Comparison of Main Application Scenarios for ASTM A333 and A334:

However, both standards cover seamless and welded processes.

Dimensions

A333 primarily targets nominal pipe sizes, while A334 focuses on metric-sized pipes.
Their outer diameter dimensions correspond as follows:

ASTM A333 and A334 differ in wall thickness specifications:

According to the standards, A333 pipes generally use average wall thickness, indicated by schedule numbers, while A334 tubes use minimum wall thickness.

Materials:
A333 and A334 share a common grading system (Grade 1 to Grade 11), but the same grade must meet different technical requirements under each standard.

1. Chemical Composition
The chemical composition requirements for the same grade are essentially consistent across both standards.

A333 has two additional grades not found in A334: Grade 4 and Grade 10.

2. Mechanical Properties
The basic mechanical properties (tensile strength, yield strength) required for the same grade of steel pipe are identical in both A333 and A334 standards.

The basic properties of Grade 4 and Grade 10 are as follows:

Mechanical Properties of Grade 4 and 10

Manufacturing Process

ASTM A333 specifies that Grade 4 steel pipes must be manufactured using a seamless process. For other grades, both seamless and welded processes are permitted.

Heat Treatment Process

Heat treatment is crucial for ensuring low-temperature toughness. Both standards require normalizing, annealing, or stress-relief heat treatment for steel pipes, but specific parameters differ.

Normalizing:

A333 requires heating to no less than 1500°F [815°C].

A334 requires heating to no less than 1550°F [845°C].

In the A333 standard, for the seamless process only, reheat and control hot working and the temperature of the hot-finishing operation to a finishing temperature range from 1550 to 1750°F [845 to 945°C]. A334 specifies this temperature range as 1550 to 1750°F [845 to 955°C].

Additionally, ASTM A333 specifies that Grade 1, 6, and 10 pipes may be heat-treated by heating to a uniform temperature of not less than 1500°F [815°C], followed by quenching in liquid and reheating to a suitable tempering temperature.

Impact Properties

Both A333 and A334 require steel pipes to pass low-temperature Charpy V-notch impact tests, except for Grade 11, which is exempt from this requirement.

Both standards specify longitudinal sampling for test specimens.

Mechanical Testing

Although both ASTM A333 and A334 are designed for low-temperature steel pipes, their application scenarios and performance requirements differ, directly influencing the scope of their mechanical testing programs.