1, Nominal size and actual size
Nominal size is the nominal size specified in the standard, it is the ideal size of the production process to give hope, but the actual production, steel is often larger or smaller than the actual size of nominal size, actual size obtained, called real Actual size. 2, deviations and tolerances Allow between actual size and the nominal size specified in the standard there is a difference, called the deviation. The difference is positive is called a positive deviation, the difference is negative is called negative deviation. Plus or minus the standard deviation of the specified absolute and called tolerance, also called the tolerance zone. Deviation absolute deviation and relative deviation points.
3, Delivery length
1) usual length: Also known as non-cut lengths. The same standard steel pipe hot-rolled and cold drawn pipe length is generally not the same, this is due to the ability of the unit caused. 2) Length Length: Orders which require a fixed length of cut. Should be within the usual length range, generally allow no positive deviation negative deviation. 3) double length: Orders which require a cut to a certain length (single foot) integer multiples. Single and double length factor should specified in the contract, the calculation should consider the total length of the double length incision margin and multiple lengths deviation. 4) short lengths: standard length is less than the lower limit of the usual length, but not less than the minimum allowed length standard. Manufacturers should avoid the generation of short-foot pipe. More and more of the existing provisions are not allowed to take the standard steel cross feet short tube. 5) Qi foot length: Also known as the length of the range. Qi foot length range than the usual length narrower. Some foreign standards Qi foot length, the concept of non-homogeneous foot length. If the user requested by Qi foot length delivery, should be specified in the contract Qi foot range. As API 5CT of a length, the length of two, three-foot length is the length of Qi. Qi foot length does not allow deviation.
4, ellipticity (roundness):
pipe ovality is the difference between the maximum outer diameter of the same cross-section and minimum outside diameter, Dmax-Dmin.
5. Bending: steel pipe is not straight in the longitudinal direction of the degree. Branch of the Ministry of curvature (also called curvature per meter) and total curvature. 6, melting ingredients and finished components: Steel melting components refers to steel smelting is completed in mid-casting chemical composition. Finished component refers to the chemical composition of finished steel (including billets) on. The same ingredients and finished steel smelting furnace components allow a deviation, which make provisions in GB / T222, at present there are GB / T222-1984 "Chemical analysis of steel samples for sampling and chemical composition of the finished product tolerance" and GB / T222-2006 "finished steel chemical composition tolerance" in two parallel (excessive) version, the overall situation is tighter than the old version of the new standards. Before 2006 the revision of domestic product standards referenced in the normative references is version 84, (undated, may also be used GB / T222-2006), 2006, after the revision of the standard three cases one is specified with the GB / T222-1984, the second is specified with the GB / T222-2006, the third is a write-only GB / T222, which means the use of GB / T222 latest version. (Some standard and user-specified version 84, 2006 in addition to the executable version, of course, we will strictly internal advocate not to loose control the ingredients). 84 version of the sampling requirements have been individually developed GB / T20066-2006 "sampling and sample preparation of samples for determination of chemical composition of steel and iron." 7, the tensile strength, yield strength, elongation The newest standard GB / T228-2002 "metal material of the metal tensile test method" requirements: tensile strength symbol Rm; and lower yield strength ReH yield strength Rel points on the yield strength, and there Rt0.5 Rp0.2. Tensile strength, yield strength in units of MPa. 1MPa = 1N / mm2,1bar = 100KPa = 0.1MPa. Elongation symbols A, in%, the proportion of foreign products standards and non-proportional test specimens (fixed gauge). Some foreign standards specified wall thickness decreases, the elongation can be reduced, which should give full attention to the mass determination.
8, impact energy:
a predetermined shape and size of the sample broken absorbed power in the next action impact test force. Commonly used impact test have U and V both samples. The so-called U and V refers notch shape. A full-size V-specimen sample (height × width) 10mm × 10mm, 3/4-size specimens 10mm × 7.5mm, half the size of the sample
Inch specimen 10mm × 5mm, or other smaller-size specimens, should pay attention to in terms of their relationship. There are longitudinal and transverse shock shock shock, try using a large sample size. API 5CT standard specifies requirements for impact specimens priority and priority transverse specimens with large size specimens. Domestic product impact energy failed retest performed in GB / T2102-1988 or GB / T2102-2006. 9, hardness: hard objects ability to resist surface indentation. Divided into Brinell hardness (HB), Rockwell hardness (HRB, HRC), etc. 10, process performance: Ability to apply their own quality testing of steel in the subsequent manufacturing process. Common process performance water pressure, flattening, bending, flaring, curling test. 11, steel grade: steel performance indicators as its code representation. Lower limit is usually expressed by the yield strength. As Q345 (A, B, C, D, E), L245, N80, S135 (135,000PSi) 12, the delivery status: Final delivery of plastic pipe deformed state processing or final heat treatment. There are commonly used steel delivery status: hot rolling, annealing, normalizing, normalizing and tempering, quenching and tempering (also known as quenching). 13, lot: according to the principles laid down in a certain number of Steel Tube inspection unit, becoming the inspection lot. The middle finger is the standard batch inspection lot instead consignment nor refers to the production batch. Note: Some foreign and domestic standards in 2008 after making provision: If the pipe is no longer a single cut after heat treatment, all from one tube pipe rolled steel taken should be regarded as a.
