Purchasing Q345B hollow sections notes on common knowledge
1) general terms (1) the delivery status Refers to the final delivery products plastic deformation or the state of the final heat treatment. Don't usually after heat treatment delivery of said hot rolled or cold drawing (rolling) or manufacturing state; After heat treatment delivery according to heat treatment state, or according to the categories called normalizing heat treatment (often), tempering, quenching, annealing condition. When ordering, delivery status should be indicated in the contract. (2) according to the actual weight delivery or delivery shall be ordered to theoretical weight Is the actual weight, delivery, product weight by weighing (weighing) weight of delivery; Theoretical weight, the delivery, the product weight is calculated on steel nominal size
1) general terms
1) delivery status
Refers to the final delivery products plastic deformation or the state of the final heat treatment. Don't usually after heat treatment delivery of said hot rolled or cold drawing (rolling) or manufacturing state; After heat treatment delivery according to heat treatment state, or according to the categories called normalizing heat treatment (often), tempering, quenching, annealing condition. When ordering, delivery status should be indicated in the contract.
(2) according to the actual weight delivery or delivery shall be ordered to theoretical weight
Is the actual weight, delivery, product weight by weighing (weighing) weight of delivery;
Theoretical weight, the delivery, the product weight is calculated according to the nominal dimension steel weight. Its computation formula is as follows (according to theoretical weight, the delivery must indicate in the contract) :
Torque tube Q345B theoretical weight per meter (steel density of 7.85 kg/dm3) formula:
W = 0.02466 (D - S) S
Type: W - torque tube Q345B theoretical weight per meter, kg/m.
D - moment of Q345B pipe nominal diameter, mm;
S - moment of Q345B pipe nominal wall thickness, mm.
(3) guarantee conditions
According to the provisions of the current standard test project and to ensure that comply with the provisions of the standard, as the guarantee conditions. Guarantee condition is divided into:
A, basic guarantee conditions (also known as will protect condition). No matter whether the customer in the contract. Must be stipulated in the standard for the inspection, and ensure the test results conform to the prescribed standards.
Such as chemical composition, mechanical properties, size deviation, surface quality and inspection, the water pressure experiment or crushed or flaring process performance experiment, will guarantee conditions.
B, protocols guarantee condition: in the standard in addition to the basic guarantee conditions, there are \"according to buyer's request, the supply and demand both sides talks things over, and in the contract note? Quot; or\" when the buyer request... , should be indicated in the contract \", and the customer, the standard of basic guarantee conditions and weiwei (such as composition, mechanical properties, size deviation, etc.) or increase inspection items, such as torque tube Q345B ovality, unequal wall thickness). The above terms and requirements, in order, by supply and demand both sides talks things over, supply the technical agreement signing and indicate in the contract. Therefore, these conditions is also known as protocols guarantee conditions. Have agreements guarantee conditions of products, is to increase.
(4) of
Standard of the \"group\" means a test unit, the inspection lot. If the batch delivery unit group, said the batch of delivery. When delivery batch big, a batch of delivery can include a few test batch; When the bulk delivery, a test batch can be divided into several batch of delivery.
The composition of the \"group\" usually has the following requirements (see the relevant standards) :
A, each batch should be from the same brand (steel grade). And the same furnace (cans), or the same furnace number, the same specifications and the same heat treatment system (furnace) of Q345B torque tubes.
B, for quality carbon steel structure tubes, fluid tubes, can be different furnace (cans) of the same brand, the same specifications and the same heat treatment system (furnace) of Q345B torque tubes.
C, torque tube welding Q345B each batch shall be made by the same brand (steel grade), the same specifications of Q345B torque tubes.
(5) high quality steel and advanced high quality steel
In GB/T699-1999 and GB/T3077-1999 standard, behind the brand with \"A\" word, for the high quality steel, and vice in general and high grade steel.
High quality steel in part or all of the following is better than that of high quality steel:
A, narrowing the scope of component content;
B, to reduce the harmful elements, such as sulfur, phosphorus, copper content;
C, the guarantee of high purity (non-metallic inclusion content less);
D, ensure higher mechanical properties and process performance.
6 vertically and horizontally
Standard according to the longitudinal, it refers to processing parallel to the direction (that is, the processing direction); Horizontal, it refers to processing direction (vertical machining namely Q345B party torque tube axial direction).
Do impact experiment, direction vertical longitudinal fracture with sample processing. Therefore calls transverse fracture; Transverse fracture of the sample with the parallel processing direction, therefore calls the longitudinal fracture.
(2) Q345B torque tube shape, size of terms
1) 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.
(2) 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".
(3) delivery length
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 rolling torque tube (extrusion and expansion) Q345B 3000 mm to 12000 mm; Torque tube cold drawing (rolling) Q345B 2000 MMM ~ 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 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, 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.
(4) uneven wall thickness
Q345B the wall thickness can't be everywhere the same moment, on the cross section and longitudinal tube body wall thickness range phenomenon exists objectively, the uneven wall thickness. In order to control the inhomogeneity, in some Q345B torque tube standard stipulated in the payment of the uneven thickness of the permission of the index, general provisions do not exceed 80% of the wall thickness tolerance (after the supply and demand both sides talks things over the execution).
(5) ovality
On the circular cross section of a torque tube Q345B exists the phenomenon of outside diameter range, 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). Torque tube to control the ovality, some Q345B standard stipulated in the ovality indicators, without the permission of the general rules for no more than the outside diameter tolerance of 80% (after the supply and demand both sides talks things over the execution).
6. Bending
Torque tube Q345B curve shaped on the length direction, use Numbers show the curve is called bending degrees. The degree of curvature of standard stipulated in the general can be divided into the following two kinds:
A, partial bending: use A meter long ruler by quantity at the maximum bending moment tube Q345B, measuring the chord high (mm), is the local bending numerical, its unit is mm/m, said method such as 2.5 mm/m. This method can also be applied to the pipe bending.
B, the total length of the total bending: use a thin line, from the pipe ends taut, measurement of Q345B party torque tube bend biggest string (mm), then computes the percentage of growth degree (in meters), namely for Q345B torque tube length of the length direction of bending.
For example: Q345B square torque tube length is 8 m, measured the maximum string 30 mm high, then the length tube bending should be followed:
0.03 present 8 m x 100% = 0.375%
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