The term seamless steel pipe

When purchasing seamless steel pipe manufacturers often ask us some technical terms.

1. Nominal size and actual size

A. Nominal size: It is the nominal size stipulated in the standard, the size expected by users and enterprises, and the size indicated in the contract.

B. Actual size: It is the actual size obtained in the production process. The size is often greater than or less than the nominal size.

2. Deviations and tolerances

A. Deviation: A difference between the actual size and the nominal size is allowed. A positive difference is called a positive difference, and a negative difference is called a negative difference.

B. Tolerance: The sum of the absolute values of the positive and negative deviations specified in the standard is called tolerance. Tolerances are non-directional.

Dimension and delivery status of seamless steel pipe in terms analysis

3. Delivery length

Delivery length is also known as user required length and contract length.

A. Usual length: also known as non-fixed length. Where the length is within the length range specified in the standard and there is no fixed length requirement, it is called the usual length.

Structural pipe standard specifies:

Hot rolled steel pipe:

Cold-rolled (drawn) steel pipe:

B. Measuring length: usually within the usual length range, it is a fixed length size required in the contract, but the actual length is impossible to cut out; Therefore, it is stipulated in the standard that a positive deviation (more than less) is allowed for the length of the ruler.

Structural pipe standard: markup requirements are generally about 10% of the base price.

C. Length of double scale: the length of double scale shall be within the usual range. The length of single scale and the multiples constituting the total length shall be indicated in the contract (for example, 3000X3, namely three multiples of 3000mm, namely 9000mm). In practice, the allowable positive deviation of 20mm should be added on the basis of the total length, plus the notch allowance should be left for each single size length. (10%)

For example, if the outer diameter of a structural pipe is less than or equal to 159mm, the outer diameter is between 5 and 10mm, and the outer diameter is larger than 159mm

D. Range length: Within the usual range, the user requires one of the fixed range lengths. This must be stated in the contract. (4%)

Example: The usual length is

The range length is

Dimension and delivery status of seamless steel pipe in terms analysis

4. Uneven wall thickness

In order to control the uniformity of wall thickness, the allowable index of non-uniformity is specified in some steel pipe standards, which generally does not exceed 80% of the wall thickness tolerance. (negotiated by both parties)

5. Ellipticity

The difference between the maximum outside diameter and the minimum outside diameter is the ovality. In order to control ovality, some steel pipe standards specify the allowable index of ovality. It is stipulated that not more than 80% of the outside diameter tolerance is agreed by both parties.

6. Bend

Steel pipe in the direction of length curve, with a number to indicate the curve is called bending degree.

A. Local bending (1m) H chord height

B. Total bending H chord height max L total length (100%)

7. Size deviation

Dimensional aberration or allowable deviation from a standard. (mainly refers to the outer diameter and wall thickness of the steel pipe)

China seamless pipe network website learned: delivery status:

Delivery state refers to the final plastic deformation or final heat treatment state of the product. In general

Delivery without heat treatment is called hot or cold rolled (drawn) or manufactured state. Passing heat

The treatment of delivery is called the heat treatment state, or according to the type of heat treatment is called normalizing (normalizing), modulation

Quality, solution, annealing state.