Introduction to Common Terms in Steel Pipe Standards

① Delivery status
It refers to the final plastic deformation or final heat treatment state of the delivered product. Generally delivered without heat treatment is referred to as the hot rolled or cold drawn (rolled) state or manufacturing state; Delivery after heat treatment is referred to as the heat treatment state, or according to the type of heat treatment, it is referred to as the normalized (normalized), quenched and tempered, solid solution, and annealed state. When ordering, the delivery status should be indicated in the contract.
② Delivery by actual weight or theoretical weight
Actual weight – At the time of delivery, the product weight is delivered according to the weighed (weighed) weight;
Theoretical weight – When delivered, the weight of the product is calculated based on the nominal size of the steel. The calculation formula is as follows (if delivery is required by theoretical weight, it shall be indicated in the contract):
The theoretical weight per meter of steel pipe (the density of steel is 7.85kg/dm3) is calculated using the following formula:
Where: W – theoretical weight of steel pipe per meter, kg/m;
D – Nominal outer diameter of steel pipe, mm;
S – nominal wall thickness of steel pipe, mm.
③ Guarantee conditions
The inspection conducted in accordance with the provisions of the current standard and ensuring compliance with the provisions of the standard are called guarantee conditions. The guarantee conditions are further divided into:
A. Basic guarantee conditions (also known as mandatory guarantee conditions). Whether or not the customer indicates it in the contract. The inspection shall be carried out in accordance with the standards and ensure that the inspection results comply with the standards.
Such as chemical composition, mechanical properties, dimensional deviation, surface quality, and process performance tests such as flaw detection, hydrostatic testing, or flattening or flaring are all necessary conditions.
B. Agreement guarantee conditions: In addition to the basic guarantee conditions, the standard also includes “according to the requirements of the demander, after negotiation between the supplier and the demander, and with a note in the contract” or “when the demander requires, “It should be noted in the contract that”; there are also customers who propose stricter requirements for the basic guarantee conditions in the standard (such as composition, mechanical properties, dimensional deviation, etc.) or additional inspection items (such as steel pipe ovality, uneven wall thickness, etc.). ” 。 The above terms and requirements shall be negotiated between the supplier and the buyer when ordering, and a supply technical agreement shall be signed and noted in the contract. Therefore, these conditions are also referred to as agreement guarantee conditions. Products with agreed warranty conditions generally require price increases.
④ Batch
“Batch” in the standard refers to an inspection unit, that is, an inspection batch. If the batch is grouped by the delivery unit, it is called the delivery batch. When the delivery batch is large, a delivery batch can include several inspection batches; When the delivery batch is small, an inspection batch can be divided into several delivery batches.
The composition of a “batch” usually has the following provisions (see relevant standards for details):
Each batch shall consist of steel pipes of the same brand (steel grade), furnace (tank) number, or parent furnace number, specification, and heat treatment system (heat).
B. For excellent carbon steel structural pipes and fluid pipes, they can be composed of steel pipes of the same brand, specification, and heat treatment system (heat) from different furnaces (tanks).
Each batch of welded steel pipes shall be composed of steel pipes of the same brand (steel grade) and specification.
⑤ Excellent steel and high-grade excellent steel
In the standards GB/T699-1999 and GB/T3077-1999, those with “A” after their brand name are high-grade excellent steels, while those with “A” after their brand name are ordinary excellent steels.
Advanced superior steel is superior to superior steel in some or all of the following:
A. Reduce the content range of ingredients;
B. Reduce the content of harmful elements (such as sulfur, phosphorus, and copper);
C. Ensure high purity (low content of non-metallic inclusions is required);
D. Ensure high mechanical and technological properties.
⑥ Vertical and horizontal
The term “longitudinal” in the standard refers to those that are parallel to the processing direction (i.e., along the processing direction); The transverse direction refers to the direction perpendicular to the processing direction (i.e., the axial direction of the steel pipe).
When performing an impact energy test, the fracture surface of the longitudinal specimen is perpendicular to the processing direction. Therefore, it is called a transverse fracture; The fracture of a transverse specimen is called a longitudinal fracture because it is parallel to the processing direction.

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