refers to the final plastic deformation or final heat treatment state of the delivered product. Generally, those delivered without heat treatment are called hot-rolled or cold-drawn (rolled) state or manufacturing state; those delivered after heat treatment are called heat-treated state, or normalized (normalized), quenched and tempered, solution, annealed according to the type of heat treatment state. When ordering, the delivery status must be indicated in the contract.
②Delivery according to actual weight or theoretical weight
Actual weight-when delivered, the weight of the product is delivered according to the weighed (weighed) weight;
Theoretical weight-at the time of delivery, the weight of the product is the weight calculated according to the nominal size of the steel. The calculation formula is as follows (if delivery is required according to the theoretical weight, it must be indicated in the contract):
Theoretical weight of steel pipe per meter (the density of steel is 7.85kg/dm3) calculation formula:
In the formula: W–theoretical weight of steel pipe per meter, kg/m;
D–the nominal outer diameter of the steel pipe, mm;
S–the nominal wall thickness of the steel pipe, mm.
Perform inspections according to the stipulated items of the current standard and ensure compliance with the stipulations of the standard, which is called the guarantee condition. The guarantee conditions are divided into:
A. Basic guarantee conditions (also known as compulsory guarantee conditions). Regardless of whether the customer indicates in the contract. It is necessary to carry out the inspection according to the standard and ensure that the inspection result meets the standard.
Such as chemical composition, mechanical properties, dimensional deviation, surface quality, and process performance tests such as flaw detection, hydraulic test or flattening or flaring are all required conditions.
B. Agreement guarantee conditions: In addition to the basic guarantee conditions in the standard, there are also “according to the requirements of the buyer, after negotiation between the supplier and the buyer, and note in the contract?” or “When the buyer requires…, it should be noted in the contract Some customers put forward stricter requirements (such as composition, mechanical properties, dimensional deviation, etc.) or additional inspection items (such as steel pipe ovality, uneven wall thickness, etc.) for the basic guarantee conditions in the standard. The above clauses and requirements, When ordering, both parties negotiate, sign the technical supply agreement and indicate in the contract. Therefore, these conditions are also called the agreement guarantee conditions. Products with the agreement guarantee conditions generally require a price increase.
The “batch” in the standard refers to an inspection unit, that is, an inspection lot. If the batch is grouped by the delivery unit, it is called the delivery batch. When the delivery lot is large, one delivery lot can include several inspection lots; when the delivery lot is small, one inspection lot can be divided into several delivery lots.
The composition of “batch” usually has the following requirements (see relevant standards for details):
A. Each batch should be composed of steel pipes of the same brand (steel grade), the same furnace (tank) number or the same parent furnace number, the same specification and the same heat treatment system (heat).
B. For high-quality carbon steel structural pipes and fluid pipes, it can be composed of steel pipes of the same brand, same specification and the same heat treatment system (heat) of different furnaces (tanks).
C, each batch of welded steel pipes should be composed of steel pipes of the same brand (steel grade) and the same specification.
⑤High-quality steel and high-quality steel
In the standards of GB/T699-1999 and GB/T3077-1999, those with “A” after their grades are high-grade high-quality steels, otherwise they are general high-quality steels.
High quality steel is superior to high quality steel in some or all of the following:
A, narrow the range of ingredient content;
B, reduce the content of harmful elements (such as sulfur, phosphorus, copper);
C, to ensure high purity (requires less non-metallic inclusions);
D, to ensure high mechanical properties and process performance.
⑥Vertical and horizontal
According to the standard, the longitudinal direction refers to those parallel to the processing direction (that is, along the processing direction); the transverse direction refers to the perpendicular to the processing direction (the processing direction is the axial direction of the steel pipe).
When doing the impact energy test, the fracture of the longitudinal specimen is perpendicular to the processing direction. Therefore, it is called the transverse fracture; the fracture of the transverse sample is parallel to the processing direction, so it is called the longitudinal fracture.