Brief introduction of common terms in steel pipe standards

① Delivery status

Refers to the final plastic deformation or final heat treatment state of the delivered product. Generally, delivery without heat treatment is called hot-rolled or cold-drawn (rolled) state or manufacturing state; Delivery after heat treatment is called heat treatment state, or according to the type of heat treatment, it is called normalizing (normalizing), quenching and tempering, solution and annealing state. When ordering, the delivery status should be indicated in the contract.

② Delivery according to 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-at the time of delivery, the product weight is the weight calculated according to the nominal size of steel. The calculation formula is as follows (if delivery is required by theoretical weight, it should be indicated in the contract):

Calculation formula of theoretical weight per meter of steel pipe (the density of steel is 7.85kg/dm3): W=0.02466*(D-S)*S

Where: W-theoretical weight of steel pipe per meter, kg/m; D-nominal outside diameter of steel pipe, mm; S-nominal wall thickness of steel pipe, mm.

③ Guarantee conditions

According to the provisions of the current standard, the project is inspected and guaranteed to meet the requirements of the standard, which is called the guarantee condition. Guarantee conditions are divided into:

A, the basic guarantee conditions (also known as guaranteed conditions). Whether or not the customer indicates it in the contract. The inspection shall be carried out according to the standard, and the inspection results shall meet the standard.

Such as chemical composition, mechanical properties, dimensional deviation, surface quality, flaw detection, water pressure test, flattening or flaring test, etc., are all necessary conditions.

B guarantee conditions of the agreement: in addition to the basic guarantee conditions, there are "according to the requirements of the buyer, negotiated by the supplier and the buyer, and noted in the contract" quot; Or "when the buyer requires ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… There are also customers who put forward stricter requirements for the basic guarantee conditions in the standard (such as composition, mechanical properties, dimensional deviation, etc.) or increase inspection items (such as ovality and uneven wall thickness of steel pipes, etc.). When ordering the above terms and requirements, the supplier and the buyer shall negotiate, sign the technical agreement for supply and indicate it in the contract. Therefore, these conditions are also called agreement guarantee conditions. Generally, the price of products with guaranteed conditions in the agreement should be increased.

④ Batch

"Batch" in the standard refers to an inspection unit, that is, an inspection lot. If the delivery unit groups batches, it is called delivery batch. When the delivery batch is large, a delivery batch can include several inspection lots; When the delivery batch is small, an inspection lot can be divided into several delivery batches.

The composition of "batch" usually has the following provisions (see relevant standards for details):

A, each batch shall be composed of steel pipes of the same brand (steel grade), the same furnace (tank) number or the same mother furnace number, the same specification and the same heat treatment system (heat times).

B for high-quality carbon steel structural pipes and fluid pipes, steel pipes of the same brand, the same specification and the same heat treatment system (heat times) of different furnaces (tanks) can be used.

C each batch of welded steel pipes shall be composed of steel pipes of the same brand (steel grade) and specification.

⑤ High-quality steel and high-quality steel

In GB/T699-1999 and GB/T3077-1999 standards, those with "A" at the back of the brand are high-grade high-quality steel, and vice versa.

High-quality steel is superior to high-quality steel in some or all of the following aspects:

A, reducing the content range of ingredients;

B, reduce the content of harmful elements (such as sulfur, phosphorus and copper);

C, ensuring high purity (requiring less nonmetallic inclusions);

And d, ensure high mechanical properties and proces properties.

⑥ Vertical and horizontal

In the standard, longitudinal direction refers to those parallel to the processing direction (i.e. along the processing direction); Transverse direction is perpendicular to the processing direction (the processing direction is the axial direction of the steel pipe).

When doing impact work experiment, the fracture of the longitudinal specimen is perpendicular to the processing direction. So it is called transverse fracture; The transverse fracture of the specimen is parallel to the processing direction, so it is called the longitudinal fracture.