| Commonly used terms in steel pipe standards |
| 1. General terms ①delivery status It refers to the state of final plastic deformation or final heat treatment of the delivered product. Generally, those delivered without heat treatment are called hot-rolled or cold-drawn (rolled) manufacturing state; those delivered after heat treatment are called heat-treated state, or normalized (normalized), quenched and tempered, solution, annealed according to the type of heat treatment . When ordering, the delivery status must be indicated in the contract. ②Delivery according to actual weight or delivery according to theoretical weight Actual weight-at the time of delivery, the weight of the product is delivered according to the weighed (weighed) weight; Theoretical weight-at the time of delivery, the weight of the product is the weight calculated according to the nominal size of the steel. The calculation formula is as follows (delivery according to the theoretical weight must be indicated in the contract): The theoretical weight of steel pipe per meter (the density of steel is 7.85kg/dm3) calculation formula: W=0.02466（D-S）S Where： W——Theoretical weight of steel pipe per meter，kg/m； D——Nominal outer diameter of steel pipe，mm； S——Nominal wall thickness of steel pipe，mm。 ③Guarantee conditions Performing inspections according to the stipulated items of the current standards and ensuring compliance with the stipulations of the standards are called guarantee conditions. Guarantee conditions are divided into： A、Basic guarantee conditions (also known as compulsory guarantee conditions). Regardless of whether the customer indicates in the contract. It is necessary to carry out the inspection according to the standard and ensure that the inspection result meets the standard. Such as chemical composition, mechanical properties, dimensional deviation, surface quality, and process performance tests such as flaw detection, hydraulic test, or flattening or flaring, are all guaranteed conditions.（021-57590365） B、Agreement guarantee conditions: In addition to the basic guarantee conditions in the standard, there is "according to the requirements of the buyer, after negotiation between the supplier and the buyer, and indicating "or" in the contract when the buyer requires..., it should be indicated in the contract"; Other customers put forward stricter requirements on the basic guarantee conditions in the standard (such as composition, mechanical properties, dimensional deviation, etc.) or increase inspection items (such as steel pipe ellipticity, uneven wall thickness, etc.). The above terms and requirements shall be negotiated by the supplier and the buyer when ordering, and the technical supply agreement shall be signed and indicated in the contract. Therefore, these conditions are also called agreement guarantee conditions. Products with agreed guarantee conditions generally have to be increased in price. ④The "batch" in the batch standard refers to an inspection unit, that is, an inspection lot. If the batch is grouped by the delivery unit, it is called the delivery batch. When the delivery lot is large, one delivery lot can include several inspection lots; when the delivery lot is small, one inspection lot can be divided into several delivery lots. The composition of "batch" usually has the following regulations (see relevant standards for details)： A、Each batch should be composed of steel pipes of the same brand (steel grade), the same furnace (tank) number or the same parent furnace number, the same specification and the same heat treatment system (heat). B、For high-quality carbon steel structural pipes and fluid pipes, they can be composed of steel pipes of the same brand, specification and heat treatment system (heat) of different furnaces (tanks). C、Each batch of welded steel pipes shall be composed of steel pipes of the same brand (steel grade) and specifications. (Tianyang Steel Pipe) ⑤High-quality steel and high-quality steel In the standards of GB/T699-1999 and GB/T3077-1999, those with "A" after their grades are high-quality steels, otherwise they are general high-quality steels. High-quality steel is better than high-quality steel in some or all of the following: A、Narrow the range of ingredient content； B、Reduce the content of harmful elements (such as sulfur, phosphorus, copper)； C、Ensure higher purity (requires less non-metallic inclusions)； D、Ensure high mechanical properties and process performance。 ⑥Portrait and landscape In the standard, the longitudinal direction refers to the one parallel to the processing direction (ie along the processing direction); the transverse direction refers to the perpendicular to the processing direction (the processing direction is the axial direction of the steel pipe)。 When doing the impact energy experiment, the fracture of the longitudinal specimen is perpendicular to the processing direction. Therefore, it is called the transverse fracture; the fracture of the transverse sample is parallel to the processing direction, so it is called the longitudinal fracture. 2. Steel pipe shape and size terms ①Nominal size and actual size A、Nominal size: the nominal size specified in the standard, the ideal size that users and manufacturers hope to obtain, and the order size specified in the contract。 B、Actual size: the actual size obtained during the production process, which is often larger or smaller than the nominal size. This phenomenon of being larger or smaller than the nominal size is called deviation。 ②Deviations and tolerances A、Deviation: In the production process, because the actual size is difficult to meet the nominal size requirement, that is, it is often larger or smaller than the nominal size, so the standard stipulates that there is a difference between the actual size and the nominal size. A positive difference is called a positive deviation, and a negative difference is called a negative deviation. B、Tolerance: The sum of the positive and negative deviation values specified in the standard is called tolerance, also called "tolerance zone". Deviation is directional, that is, expressed as "positive" or "negative"; tolerance is not directional, so it is wrong to call the deviation value "positive tolerance" or "negative tolerance". ③Delivery length Delivery length is also called the length required by the user or the length of the contract. The standard has the following regulations on delivery length: A、Normal length (also known as non-fixed length length): Any length within the standard specified length and no fixed length requirement is called normal length. For example, the structural pipe standard stipulates: hot-rolled (extruded, expanded) steel pipe 3000mm~12000mm; cold drawn (rolled) steel pipe 2000mm~10500mm. B、Cut-to-length length: The cut-to-length length should be within the usual length range, which is a certain fixed length dimension required in the contract. However, it is impossible to cut out the cut-to-length length in actual operation, so the standard stipulates the allowable positive deviation value for the cut-to-length length. Take the structural pipe standard as： The yield rate of production of fixed-length pipes is much lower than that of normal-length pipes, and it is reasonable for manufacturers to request price increases. The rate of price increase varies from company to company. Generally, the price increase is about 10% on the basis of the base price. (Shanghai Tianyang) C、Length of multiple ruler: The length of the multiple ruler should be within the range of normal length. The contract should indicate the length of the single ruler and the multiple of the total length (for example, 3000mm×3, which is 3 multiples of 3000mm, and the total length is 9000mm). In actual operation, the allowable positive deviation of 20mm should be added to the total length, plus a margin for the incision of each single ruler length. Take the structural pipe as an example, the allowance for cutting is stipulated: 5-10mm for outer diameter ≤159mm; 10-15mm for outer diameter >159mm. If there is no double-length deviation and cutting allowance in the standard, it should be negotiated by the supplier and the buyer and indicated in the contract. The double-length scale is the same as the fixed-length length, which will bring about a substantial reduction in the yield rate of the manufacturer. Therefore, it is reasonable for the manufacturer to raise the price, and the price increase is basically the same as the fixed-length length. D、Range length: The range length is within the usual length range. When the user requires one of the fixed range lengths, it must be indicated in the contract. For example: Usually the length is 3000~12000mm, and the range cut-to-length length is 6000~8000mm or 8000~10000mm. It can be seen that the range length is looser than the fixed-length and double-length length, but it is much stricter than the usual length, which will also reduce the yield of production enterprises. Therefore, it is reasonable for the manufacturer to raise the price, and the price increase is generally about 4% above the base price. ④Uneven wall thickness The wall thickness of steel pipes cannot be the same everywhere, and there are objectively unequal wall thicknesses in the cross section and longitudinal pipe body, that is, uneven wall thickness. In order to control this non-uniformity, some steel pipe standards stipulate the allowable index for uneven wall thickness, which is generally specified not to exceed 80% of the wall thickness tolerance (implemented after negotiation between the supplier and the buyer). ⑤Ovality There is a phenomenon of unequal outer diameters in the cross-section of the round steel pipe, that is, there are large and small outside diameters that are not necessarily perpendicular to each other. The difference between the large and small outside diameters is the ellipticity (or non Roundness). In order to control the ovality, some steel pipe standards stipulate the allowable index of ovality, which is generally specified as not exceeding 80% of the outer diameter tolerance (implemented after negotiation between the supplier and the buyer). ⑥Curvature The steel pipe is curved in the length direction, and the degree of curve is called the degree of curvature, which is indicated by numbers. The curvature specified in the standard is generally divided into the following two types: A、Local curvature: Measure the chord height (mm) with a one-meter straight ruler on the bend of the steel pipe, which is the value of local curvature. The unit is mm/m, and the expression method is 2.5mm/m. This method is also suitable for tube end curvature. B、全長總彎曲度：用一根細繩，從管的兩端拉緊，測量鋼管彎曲處大弦高（mm），然后換算成長度（以米計）的百分數，即為鋼管長度方向的全長彎曲度。 例如：鋼管長度為8m，測得大弦高30mm,則該管全長彎曲度應為： 0.03÷8m×100%=0.375% ⑦尺寸超差 尺寸超差或叫尺寸超出標準的允許偏差。此處的“尺寸”主要指鋼管的外徑和壁厚。通常有人把尺寸超差習慣叫“公差出格”，這種把偏差和公差等同起來的叫法是不嚴密的，應叫"偏差出格"。此處的偏差可能是"正"的，也可能是“負”的，很少在同一批鋼管中出現“正、負”偏差均出格的現象。 三、化學分析術語 鋼的化學成分是關系鋼材質量和終使用性能的重要因素之一，也是編制鋼材，乃至終產品熱處理制度的主要依據。因此，在鋼材標準的技術要求部分，往往規定了鋼材適用的牌號（鋼級）及其化學成分，并以表格形式列入標準中，是生產企業和客戶驗收鋼及鋼材化學成分的重要依據。(www.steeltube-cn.com) ①鋼的熔煉成分 一般標準中規定的化學成分即指熔煉成分。它是指鋼冶煉完畢、澆注中期的化學成分。為使其具有一定代表性，即代表該爐或罐的平均成分，在取樣標準方法中規定，將鋼水在樣模內鑄成小錠，在其上刨取或鉆取樣屑，按規定的標準方法（GB/T223）進行分析，其結果必須符合標準化學成分范圍，也是客戶驗收的依據。 ②成品成分 成品成分又叫驗證分析成分，是從成品鋼材上按規定方法（GB/T222）鉆取或刨取樣屑，并按規定的標準方法（GB/T223）進行分析得來的化學成分。鋼在結晶和以后塑性變形中，因鋼中合金元素分布的不均勻（偏析），因此允許成品成分與標準成分范圍（熔煉成分）之間存在有偏差，其偏差值應符合GB/T222之規定。 鋼材的成品成分主要是供使用部門或質量檢驗部門驗收鋼材質量使用的，生產企業一般不做成品分析（用戶要求者除外），但應保證成品分析符合標準規定。 ③仲裁分析 由于兩個實驗室分析同一樣品的結果有顯著差別并超出兩個實驗室的允許分析誤差，或者生產企業與使用部門、需方與供方對同一樣品或同一批鋼材的成品分析有分歧意見時，可由第三方具有豐富分析經驗的權威單位（如中國鋼鐵研究總院或具有商檢資格的檢驗部門）進行再分析，即稱之謂仲裁分析。仲裁分析結果即為終判定依據。 |
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