Steel Pipe Standards Are Commonly Used In Terminology.

(1) general term

Delivery status

Refers to the final plastic deformation or final heat treatment of the delivery product. The state or manufacturing state of a hot rolling or cold drawing (rolling) which is generally not delivered by heat treatment; After heat treatment, the condition of heat treatment, or according to the type of heat treatment, is called normalizing (normalizing), tempering, solid solution, annealing. When ordering, the delivery status should be noted in the contract.

To be delivered by actual weight or by theoretical weight.

Actual weight - when delivered, the weight of the product is delivered in weight (over weight);

Theoretical weight - when delivered, the weight of the product is calculated according to the nominal size of the steel. The calculation formula is as follows (the requirement to be delivered by theoretical weight shall be indicated in the contract) :

The theoretical weight of steel tube per meter (steel density is 7.85kg/dm3) formula:

W=0.02466* (d-s) *S.

In the formula: W-- the theoretical weight of each meter of steel pipe, kg/m;

D-- nominal external diameter of steel pipe, mm;

S-- the nominal wall thickness of steel pipe, mm.

Guarantee condition

To inspect and ensure compliance with the standards set forth in the current standard, which is called guarantee conditions. The guarantee conditions are divided into:

A, the basic guarantee condition (also called the guarantee condition). Whether or not the customer indicates in the contract. The inspection shall be carried out in accordance with the standards, and the test results shall meet the standard requirements.

Such as chemical composition, mechanical properties, dimensional deviation, surface quality, and test of test, hydraulic pressure test, or compression or expansion, are required.

B. Guarantee conditions of the agreement: in addition to the basic guarantee conditions in the standard, "in accordance with the requirements of the demander, through consultation between the two parties, and in the contract?" Quot; "Or" when the buyer asks... In the contract, "; In addition, the basic guarantee conditions of the standard are proposed to impose strict requirements (such as components, mechanical properties, dimensional deviation, etc.) or to increase the inspection items (such as the ellipticity of the steel tube and the uneven wall thickness). The above terms and requirements shall be negotiated by both parties and signed by the supply and demand parties during the order, and shall be indicated in the contract. Therefore, these conditions are also known as agreement guarantee conditions. The product that has agreement guarantee condition, want to add price commonly.

(4) of

The "batch" in the standard refers to a unit of inspection, that is, inspection approval. If the delivery unit group is approved, the delivery is called. When the delivery volume is large, a delivery batch may include several inspection batches. When the delivery volume is small, one inspection batch can be divided into several delivery batches.

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

A. Each batch shall consist of the same number (steel grade), the same furnace (pot) number or the same mother furnace number, the same specification and the same heat treatment system (furnace number).

B. For high-quality carbon steel structure pipes and fluid pipes, the same number, the same specification and the same heat treatment system (furnace times) of different furnaces can be formed.

C. Each batch of welded steel tubes shall be composed of the same brand (steel grade) and steel pipe of the same specification.

High quality steel and high quality steel.

In GB/ t699-1999 and GB/ t3077-1999, there is A" A" in the back of its brand name, which is superior quality steel and vice versa.

Superior quality steel is superior to quality steel in the following parts or all:

A. Narrow the range of components;

B. Reduce the content of harmful elements such as sulphur, phosphorus and copper;

C. Ensure high purity (require less metal inclusion);

D. Ensure high mechanical performance and process performance.

It's vertical and horizontal.

In the standard, vertical refers to the parallel processing direction (that is, the processing direction); Lateral refers to the direction perpendicular to the processing direction (the direction of machining is the axial direction of the steel tube).

The fracture of the longitudinal specimen is perpendicular to the processing direction when conducting the impact work experiment. It is called transverse fracture; The fracture of transverse specimen is parallel to the machining direction, so it is called longitudinal fracture.

(2) steel tube shape, dimension term.

Nominal size and actual size.

A, nominal size: it is the nominal size specified in the standard, which is the ideal size that users and manufacturers want to get, as well as the order size indicated in the contract.

B. Actual size: the actual size obtained in the production process, which is usually larger than or less than nominal size. This phenomenon of greater than or less than nominal size is called deviation.

Deviation and tolerance.

A, deviation: in the process of production, due to the difficult to meet the requirements of nominal size, actual size is often greater than or less than the nominal size, so the standard stipulated in the actual size and there is A difference between nominal size allowed. A positive deviation of positive value and a negative deviation of a negative value.

B. Tolerance: the sum of positive and negative deviation values specified in the standard is called tolerance, also known as "tolerance zone".

The deviation is directional, meaning "positive" or "negative"; Tolerance is not directional, so it is wrong to call the deviation value "positive tolerance" or "negative tolerance".

Delivery length

The length of delivery is also known as the length or length of the contract. There are several requirements for the length of delivery in the standard:

A, usually length (also known as non-fixed-length length) : the length of any length within the length of the standard and without A fixed length requirement is called the usual length. For example, the structure pipe standard stipulates: hot rolling (extrusion, expansion) steel pipe 3000mm ~ 12000mm; Cold drawn (rolled) steel pipe 2000mmm ~ 10500mm.

B. Length of length: the length of the fixed length shall be within the usual length range and shall be a fixed length dimension required in the contract. However, it is not possible to cut out the absolute length in actual operation. Therefore, the allowable positive deviation value is specified in the standard.

The structural management standards are as follows:

It is reasonable that the production enterprise puts forward the price increase requirement. The price range of each enterprise is not consistent, generally base price on the basis of about 10%.

C, the length of the length: the length of the length shall be within the usual length range. The length of the single length and the multiple of the total length shall be indicated in the contract (for example, 3000mm x 3, 3 times of 3000mm, and the total length is 9000mm). In actual operation, the allowable positive deviation of 20mm should be added on the basis of the total length, and the margin of incision should be retained for each single size. Taking the structural tube as an example, the residual amount of the incision is specified: the outer diameter is less than 159mm and is 5 ~ 10mm; Outside diameter > 159mm is 10 ~ 15mm.

If the standard deviation and cutting allowance are not specified in the standard, both parties shall negotiate and specify in the contract. Times the length scales as specified length, will bring enterprises yield significantly lower, so the production enterprise put forward the price is reasonable, the mark-up with specified length mark-up on basic same.

D. Range length: the range length is within the usual length range. When the user asks for a fixed range length, it should be indicated in the contract.

For example: the usual length is 3000 ~ 12000mm, and the range of the length is 6000 ~ 8000mm or 8000 ~ 10000mm.

It can be seen that the range length is less than the length of the ruler and the length of the scale, but it is much stricter than the usual length, which will also bring down the production rate of the production enterprises. Therefore, it is reasonable for the manufacturer to raise the price, and the price increase is generally about 4%.

Uneven wall thickness

The thickness of steel tube wall can not be the same everywhere, in its cross section and vertical pipe body, there is an objective existence of wall thickness inequality, that is, the wall thickness is not equal. In order to control this inhomogeneity, the allowable index of wall thickness is stipulated in some steel pipe standards, and the general rule is not more than 80% of the tolerance of wall thickness (after consultation between the supply and demand parties).

(5) ovality

Exists in the cross section of a circular steel tube with diameter ranging from phenomenon, namely there is not necessarily perpendicular, minimum and maximum overall diameter diameter is the largest diameter of which is the difference between the smallest diameter ovality (or not roundness). In order to control the ellipticity, the allowable index of the ellipticity is stipulated in some steel pipe standards, and the general rule is that 80% of the outer diameter tolerance is not exceeded (implemented after consultation between the supply and demand parties).

6. Bending

The steel tube curves in the direction of length, and the curve of the steel tube is called curvature. The bending degree stipulated in the standard is generally divided into the following two types:

A. Local bending: the maximum bending of the steel tube is measured by the length of one meter long, and its string height (mm) is measured, which is the local bending value. The unit is mm/m, and the method is like 2.5mm/m. This method also applies to the bending of the tube end.

B, the total length of the total bending: use a thin line, from the pipe ends taut, measuring steel pipe bend biggest string high (mm), and then reduced the percentage of growth degree (in meters), is the length of the steel tube length direction curvature.

For example, the length of steel tube is 8m, and the maximum string height is 30mm, then the length of the pipe should be:

0.03 present 8 m x 100% = 0.375%

Size difference

Tolerances of size or size exceeding the standard. The "size" here mainly refers to the outside diameter and wall thickness of the steel pipe. In general, some people refer to the "tolerance" as "tolerance", which is called "deviation out of the box". The deviation here may be "positive" or "negative", and it is rare to see "positive and negative" deviations in the same steel tube.