Nominal size and actual size A, nominal size: size is specified in the standard name, is the ideal size of users and manufacturers hope to get,...
Nominal size and actual size
A, nominal size: size is specified in the standard name, is the ideal size of users and manufacturers hope to get, is also stated in the contract to the order of size.
, the actual size: B is given in the production process of actual size, the size is often greater than or less than the nominal size. This is greater than or less than the nominal size of the phenomenon known as deviation.
The 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. Difference between positive deviation, is called differential negative is called negative deviation.
B, tolerance: standard specified in the positive and negative deviation value is the sum of absolute value is called tolerance, also called "tolerance zone".
Deviation is a direction, namely to "positive" or "negative" said; Tolerance is no direction, therefore, called the deviation value is "tolerance" or "negative tolerance is wrong to call it".
The length of delivery
The delivery length and length according to user requirements or the length of the contract. In the standard of delivery length with the following provisions:
Length (also called A, usually not specified length) : all the length within the length of the prescribed standards and no fixed length requirements, is usually the length. Such as structural pipe standards: hot rolled steel pipe (extrusion, expanding 3000 mm to 12000 mm; Steel pipe cold drawing (rolling) MMM 2000 ~ 10500 mm.
B, the specified length: specified length should be in usually length range, the requirements of the contract is a fixed length. But in practice are cut into absolute specified length is unlikely, so the standard to the specified length in the deviation values are allowed.
To the criteria of tube structure:
The production scale length of the tube, the length of the tube yield declines larger than usual, manufacturing enterprises put forward price demand is reasonable. Mark-up on various enterprises differ, is generally based on the basic price extra 10% or so.
C, foot length: times ruler length should be within the scope of the usually length, the contract shall indicate the haploid feet in length and constitute a total length of multiples (such as 3000 mm x 3, which is 3000 mm 3 multiples, length is 9000 mm). Practice, should be on the basis of the total length and allow deviation is 20 mm, plus each haploid feet should leave a margin incision length. Tube structure, for example, rules remain incision cushion: outer diameter 159 mm or less for 5 ~ 10 mm; For 10 ~ 15 mm outside diameter > 159 mm.
Unless otherwise stipulated in the standard times ruler and the provisions of the length deviation and cutting allowance should be made by supply and demand both sides negotiate and indicate in the contract. Times as specified length, foot length to yield significantly lower production enterprise, so enterprises put forward the price is reasonable, the mark-up with specified length mark-up on basic same.
D, scope, length: the length range in length range, usually when the user requirements of a range of fixed length, need to indicate in the contract.
For example: usually length 3000 ~ 3000 mm, and the range of specified length is 6000 ~ 8000 mm or 8000 ~ 10000 mm.
Visible, foot length range than the length and the length times for loose, but more than the usual length and yan, will also bring yield of lower production enterprises. Production enterprises put forward the price is reasonable, therefore, the mark-up on basic pay extra 4% or so in general.
Uneven wall thickness
Steel tube wall thickness is not the same, may in the cross section and longitudinal pipe body wall thickness range phenomenon exists objectively, the uneven wall thickness. In order to control the inhomogeneity, in some prescribed the uneven thickness of steel tube allows index, general provisions do not exceed 80% of the wall thickness tolerance (after the supply and demand both sides talks things over the execution).
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The Future of Steel Pipe Development
The future of steel pipe development is looking promising, according to expert analysis and data. The price of carbon steel pipe is predicted to bounce back this year, with China leading the way in increasing steel consumption demands. This is due to a series of government initiatives aimed at stimulating domestic demand, including the construction of affordable housing and infrastructure projects. The demand for structural steel pipe is also on the rise, thanks to state investment in housing and engineering projects. With private investment projects also gaining popularity, the steel pipe market is set to thrive in 2017.
