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Precision Steel Tube Bright Thick Wall Seamless Steel Tube 45# Seamless Tube Wholesale Support Cutting
The length of delivery
Delivery length is also called customer required length or contract
length. The standard has the following provisions on delivery
length:
A, ordinary length (also known as irregular length) : where the
length is within the standard length range and there is no fixed
length requirements, are called ordinary length. For example,
structural pipe standards: hot rolled (extruded, expanded) steel
pipe 3000mm ~ 12000mm; Cold-drawn (rolled) steel pipe 2000mm ~
10500mm.
B. Fixed length: the fixed length shall be within the normal length
range and is a fixed length specified in the contract. But in
practice, it is impossible to cut absolute length, so the standard
stipulates the allowable positive deviation value for the length of
definite length.
The structural pipe standard is:
The yield of fixed length pipe decreases more than that of normal
length pipe, so it is reasonable for the manufacturer to raise the
price. Add price range each enterprise is not consistent, add price
10% or so on base price foundation commonly.
C. Length of multiples: the length of multiples shall be within the
normal length range, and the single length and the multiple of the
total length shall be indicated in the contract (e.g. 3000mm×3,
i.e. 3000mm 3x, with a total length of 9000mm). In practice, the
allowable positive deviation of 20mm should be added to the total
length, plus the incision allowance should be left for each single
ruler length. Take the structural pipe as an example, the specified
incision allowance: outer diameter ≤159mm is 5 ~ 10mm; Outer
diameter >159mm is 10 ~ 15mm.
If there is no length deviation and cutting allowance in the
standard, it shall be indicated in the contract through negotiation
between the supply and demand parties. Double ruler length is the
same as fixed ruler length, which will greatly reduce the yield of
production enterprises. Therefore, it is reasonable for the
production enterprises to raise the price, which is basically the
same as the fixed ruler length.
D. Range length: the range length is within the usual range. If the
user requires a fixed range length, it shall be indicated in the
contract.
For example, the length ranges from 3000 mm to 12000mm, and the
length ranges from 6000 mm to 8000mm or 8000mm to 10000mm.
It can be seen that the range length is more relaxed than fixed
length and multiple length, but it is much stricter than the usual
length, which will also reduce the yield of production enterprises.
Because this production enterprise puts forward add price is
reasonable, its add price range is in base price commonly add price
4% left and right sides.
Uneven wall thickness
Steel tube wall thickness can not be the same everywhere, there is
an objective phenomenon of unequal wall thickness in its cross
section and longitudinal tube body, that is, uneven wall thickness.
In order to control this unevenness, the allowable index of wall
thickness unevenness is stipulated in some steel pipe standards.
Generally, it is not more than 80% of wall thickness tolerance
(implemented after negotiation between the supply and demand
parties).
ovality
The phenomenon of unequal outer diameters exists in the cross
section of circular steel pipe, that is, the difference between the
maximum outer diameter and the minimum outer diameter is
ellipticity (or unroundness). In order to control the ovality, some
steel pipe standards stipulate the allowable index of the ovality,
which is generally not more than 80% of the outer diameter
tolerance (implemented after negotiation between the supply and
demand parties).
bending
The length of the steel pipe is curvilinear, and its curvilinear
degree is called bending degree. The bending specified in the
standard is generally divided into the following two kinds:
A. Local bending: measure the maximum bending point of the steel
pipe with A one-meter ruler and measure its chord height (mm),
which is the value of local bending. The unit is mm/m and the
expression method is as follows: 2.5mm/m. This method also applies
to pipe end bending.
B. Total bending of the whole length: measure the maximum chord
height (mm) at the bending point of the steel pipe with a thin
rope, and then convert the percentage of length (in meters) to the
total bending of the length direction of the steel pipe.
For example: the length of steel pipe is 8m, and the maximum chord
height measured is 30mm, then the full length bending of the pipe
should be 0.03÷8m×100%=0.375%