B, protocol to ensure conditions: standard In addition to the basic guarantee for the condition, there are "based on the demand side requirements by both supply and demand consultation and note in the contract? quot; or when required request ..., should be specified in the contract; some customers, the basic guarantee of the standard conditions of tightened requirements (such as composition, mechanical properties, size deviation, etc.) or increase the test items (such as steel pipe oval, uneven wall thickness, etc.). The above terms and requirements, in order, by both supply and demand consultation, agreement and signed the technical delivery specified in the contract. Therefore, these conditions are also known as an agreement to guarantee conditions. There is an agreement to ensure the conditions of the product, generally fare increase.
Of ④ approved standards "approved" means an inspection units, namely the inspection lot. If the batch delivery unit group, said the consignment. When the volume delivery, a consignment may include several test batches; delivery batch came from an inspection lot can be divided into several consignments.
"Batch" composition usually has the following provisions (see the relevant standards):
A, each batch should be the same grade (steel grade), the same stove (pot) or the same mother furnace of the same specifications and the same heat treatment (furnace) steel.
Quality carbon steel tubes, fluid tubes, can be the same grades of the different furnaces (cans) of the same specifications and the same heat treatment (furnace) steel.
C, welded steel pipes each batch should be the same grade (steel grade), of the same specifications of the steel pipe.
⑤ high quality steel and high quality steel. GB/T699-1999 and GB/T3077-1999 standard grades behind with the letter "A" who, for the high quality steel, contrary to the generally high quality steel.
High quality steel in the following part or all is better than high quality steel:
And narrow the range of ingredients;
B, to reduce the harmful elements (such as sulfur, phosphorus, copper) content;
C, to ensure higher purity (requiring non-metallic inclusion content);
D, to ensure high mechanical and technological properties.
⑥ vertical and horizontal. The standard longitudinal means parallel to the machining direction (ie, along the processing direction) who said; horizontal is perpendicular to the machining direction (machining direction of the steel tube axial). Do impact energy experiment, the longitudinal sample of the fracture surface perpendicular to the machining direction. It is called a transverse fracture; the fracture of the transverse specimens parallel with the processing direction, it said longitudinal fracture.
(2) steel pipe shape, size, terms
The ① nominal size and actual size
A, Size: the nominal size specified in the standard, users and producers want to get their ideal size, order size is also specified in the contract.
B, actual size: the actual size of the production process, 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 is called deviation.
② deviation and tolerance
Deviation: in the production process, due to the actual size is difficult to reach the public, said the size requirements that are often greater than or less than the nominal size, so the standard set forth in the actual size and nominal size between allowed a difference . The difference is positive is called a positive deviation, the difference is negative is called the negative deviation.
B, and tolerance: the standard set forth in positive, negative deviation of the absolute values and is called tolerance, also called the "tolerance zone". Deviation is directional, ie, "positive" or "negative"; tolerance is non-directional, therefore, the deviation of called "tolerance" or "negative tolerance" it is called a mistake.
③ delivery length. Delivery length, also known as the user requirements of the length or contract length. Standard delivery length of the following provisions:
A, the usual length (also known as non-definite length): Where the length of the standard length and fixed length requirements are referred to as the usual length. Such as structural tube standard provides: hot rolled (extrusion, expansion) steel tubes 3000mm ~ 12000mm; cold drawn (rolled) steel pipe 2000mmm ~ 10500mm.
B, Length Length: Length of the length should be within the range of the usual length of the contract requirement of a fixed length size. But the actual operation to cut out absolutely definite length is unlikely, so the standard length length regulations allow positive deviation.
Structured regulatory standards:
Production of definite length pipe to a larger decline in finished product rate than the usual length of pipe manufacturers proposed fare increase is a reasonable request. Enterprises of the rate of increase is not consistent, generally the base price on the basis of the fare increase by about 10%.
C, double length: double length should be within the range of the usual length, the contract should indicate the haplotype length and composition of the total length of multiples (eg 3000mm × 3, 3 multiples of 3000mm, total length is 9000mm). Actual operation on the basis of the total length of plus allow positive deviations 20mm, coupled with each haplotype length should be cutting margin. Structural tube, for example, require to stay incision margin: OD ≤ 159mm 5 ~ 10mm; external diameter> 159mm 10 ~ 15mm.
Standard double length deviation and the cutting margin requirement, the supply and demand should both parties and specified in the contract. Times longer scale length length, will give the producers to bring a significant reduction in the rate of finished manufacturers fare increase is reasonable, the rate of increase is basically the same as the rate of increase with length length.
D, scope length: range length in the range of usual length, the length of the user's requirements at a fixed range, need to specify in the contract.
For example: usually a length of 3000 ~ 12000mm, while the scope of definite length is 6000 ~ 8000mm or 8000 ~ 10000mm.
Visible range length than the length and double length requirements relaxed than usual length plus strict many, will bring to the production enterprises to reduce the rate of finished. Manufacturers proposed fee increases are justified, and its rate of increase in general fare increase of 4% on the base price.
④ uneven wall thickness. The pipe wall thickness can not be everywhere the same objective in its cross-sectional and longitudinal tube wall thickness ranging phenomenon, that is, uneven wall thickness. Provisions uneven wall thickness to allow indicators in order to control this non-uniformity in some steel standards and general provisions do not exceed 80% of the wall thickness tolerances (after a consultation between the execution).
⑤ ellipticity. In the cross section of the circular steel tube with outer diameter ranging phenomenon, that is, there is not necessarily perpendicular to each other the maximum outside diameter and minimum diameter, maximum diameter and minimum diameter difference is the ellipticity (or not roundness). Ellipticity allows indicators in order to control the ellipticity, and some steel pipe standard provisions, general provisions for no more than 80% of the diameter tolerance (after a consultation between the execution).
(6) curvature. Pipe in the length direction of a curve shape, the figures show the degree of the curve, called the curvature. Specified in the standard curvature is generally divided into the following two:
A, the local curvature: a meter long ruler by the amount of steel pipe bend, measured chord height (mm), is the local curvature value, in units of mm / m, indicating methods such as 2.5mm / m. This method also applies to the curvature of the pipe end.
The percentage of B, the total length of the total curvature: a string from the tube at both ends taut, measure steel pipe bend chord height (mm), and then converted to grow degrees (in meters) , that is, the total length of steel pipe length direction of curvature. For example: Pipe length 8m, measured maximum chord height 30mm, the pipe total length of curvature should be: 0.03 ÷ 8m × 100% = 0.375%
The ⑦ size tolerance. The size of ultra-poor, or call sizes beyond the standard tolerances. Here the "size" refers to the diameter and wall thickness of the steel pipe. Was usually the size of ultra-poor used to call "tolerance bounds, bias and tolerance, it is called equated this is imprecise and should be called the" deviation bounds. The deviation here may be "positive", it could be "negative" to positive and negative deviations were outrageous phenomenon rarely appear in the same batch of steel pipe.
(3) chemical analysis of terminology
The chemical composition of steel is the relationship between the quality of steel and an important factor in end-use performance, is one of the preparation of steel, and even the main basis for the final product heat treatment system. Therefore, ask some of the steel standard technology, often the first item on the provisions of the applicable grades of steel (steel grade) and its chemical composition, in tabular form included in the standard, manufacturers and customer acceptance of steel and steel chemical composition an important basis.
① steel melting ingredients. The general standards set forth in the chemical composition of referring to the melting ingredients. It refers to the finished steel smelting, pouring the chemical composition of the medium-term. If it is to have a certain representation, which represents the average composition of the furnace or tank specified in the sampling standard method, the molten steel cast in a kind of mold ingots, planing to take on or drill sample cuttings, according to the required standards methods (GB/T223) analysis, the results must conform to the standard chemical composition range of customer acceptance.
② finished composition. The finished composition is also called to verify the analysis component, from the finished steel, according to the regulations methods (GB/T222), drill or planing sampling crumbs, in accordance with the provisions of the standard method (GB/T223) analysis of chemical composition. Steel in the crystallization and after plastic deformation, due to the steel alloying elements to the uneven distribution (segregation), thus allowing the finished composition with the standard composition range (melting components) between the deviation, the deviation should in GB/T222 the provisions of .
Steel finished components for user departments or quality inspection department of the acceptance quality of steel used in manufacturing enterprises generally do not do product analysis (user requirements), but should ensure that the product analysis to meet the standard requirements.
The ③ arbitration. Two laboratory analysis of the results of the same sample, a significant difference between and beyond the two laboratories to allow analysis of the error, or production enterprises and user departments, the demand-side and supply-side differences of opinion on the same samples or with a group of steel product analysis , by the third party has a rich experience in analyzing the authority of the unit (such as the China Iron and Steel Research Institute or the commodity inspection qualified inspection department), re-analysis, that is known that the arbitration analysis. Arbitration analysis shall be final judgment basis.
(4) mechanical properties of terms
The mechanical properties of steel is to ensure that an important indicator of the steel end-use properties (mechanical properties), it depends on the chemical composition and heat treatment of steel. Steel standards, according to different requirements, the provisions of the tensile properties (tensile strength, yield strength or yield point elongation) and hardness, toughness, user requirements, high and low temperature performance.
① tensile strength (σb). The sample during the tensile pull off bear most strongly (Fb), derived from a sample of the original cross-sectional area (So), stress (σ), known as the tensile strength (σb) in N/mm2 (MPa). It said the maximum capacity to resist destruction of metallic materials under tension. Calculated as follows: σb = Fb / So
Where: Fb - bear in the sample pulled off the most vigorously, N (Newton);
So - the original specimen cross-sectional area, mm2.
(2) the yield point (σs of). Yield the phenomenon of metal materials, the sample does not increase during the tensile force (remains constant) can continue elongation when the stress known as the yield point. If the force drop occurred, you should distinguish between upper and lower yield point. The yield point of the unit is in N/mm2 (MPa).
Yield point (σsu): The specimen occurred to yield the maximum stress and force the first drop;
Yield point (σsl): yield minimum stress in the stage when excluding the initial transient effect.
The yield point is calculated as follows: σs = Fs / So
Where: Fs in - sample the stretching process yield force (constant), N (Newton);
So - the original specimen cross-sectional area, mm2.
③ Elongation (σ). In the tensile test, the specimen fractured a percentage of the gauge to increase the length of the original gauge length, called elongation. Σ, said the unit is%.
Calculated as follows: σ = (L1 - L0) / L1
Where: the L1 - fractured standard gauge length, mm;
L0 - the original specimen gauge length, mm.
(4) cross-section contraction rate (ψ). In the tensile test, the specimen fractured its shrink the diameter at the cross-sectional area of the maximum reduction in the percentage of the original cross-sectional area, known as section shrinkage. Ψ expressed in%.
Calculated as follows: of ψ = (S1-S0) / S1
Where: S0 - the original specimen cross-sectional area, mm2;
S1 - fractured necking at the minimum cross-sectional area, mm2.
⑤ hardness index. Metallic materials against hard objects indentation of the surface, known as hardness. Depending on the test method and scope of application, the hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, hardness and high temperature hardness. Commonly used for pipe, Brinell, Rockwell, Vickers hardness of three kinds.
A Brinell hardness (HB)
Ball or carbide ball of a certain diameter, the required test force (F) pressed into the pattern surface, removable by the provisions of time after the test force, indentation measurement surface of the specimen diameter ( L). Brinell hardness value is the test force divided by the quotient of indentation of spherical surface area. HBS (ball), the unit is in N/mm2 (MPa). Is calculated as follows: HB = F / π (d / 2) ²
Where: F - pressed into the metal surface of the specimen test force, N;
D - test with steel ball diameter, mm;
d - average indentation diameter, mm.
Determination of the Brinell hardness is more accurate and reliable, but generally HBS applies only to 450N/mm2 (MPa) below the metal materials, NA hard steel or thin plate. Steel standards, the Brinell hardness of the most widely used, often to the indentation diameter d to represent the hardness of the material, intuitive, and convenient.
Example: 120HBS10/1000130: with diameter 10mm steel ball under the action of the test force 1000Kgf (9.807KN), keep the 30s (seconds) measured the Brinell hardness value of 120N / mm2 (MPa).
Rockwell hardness (HK)
Rockwell hardness test, Brinell hardness test, indentation test method. Different is that it is measuring the depth of the indentation. Ie, early the Yong test force (Fo) and total force (F) has the role of the head (the steel cone or ball) pressed into the surface of the specimen by the provisions of the time, removable test force, measurement of the residual indentation depth increment (e) to calculate the hardness value. Its value is unknown the number, the symbol HR, with A, B, C, D, E, F, G and H, K, etc. 9 ruler ruler. Commonly used in steel hardness test scale for general A, B, and C, that is, the HRA, HRB, HRC.
The hardness value is calculated using the formula:
When using the A and C ruler test, HR = 100-e
When you use the B-scale test, HR = 130-e
Where e - residual indentation depth increment, the Department to require the unit 0.002mm said, when the indenter axial displacement of a unit (0.002mm), which is equivalent to a Rockwell hardness change a number. e higher the value, the lower the hardness of the metal, otherwise the hardness of the higher.
The scope of application of the three rulers are as follows:
HRA (diamond cone indenter) 20-88
HRC (diamond cone indenter) 20-70
HRB (diameter 1.588mm steel ball indenter) 20-100
The Rockwell hardness test is a very wide application, including HRC steel pipe standards after the Brinell hardness of HB. Rockwell hardness is applicable to the determination of extremely soft to extremely hard metal material, it makes up for the Brinell method is not higher than the Brinell method is simple, can be directly read from the dial of the hardness machine hardness value. However, because of its small indentation hardness values as Brinell method is accurate.
Vickers hardness (HV)
The Vickers hardness test is also a indentation test methods, test selected in 1360 a relative surface angle being quadrangular pyramidal diamond indenter force (F) pressed into the test surface, the provisions of hold time, drop the test force, and two diagonal measurement of the indentation length.
Vickers hardness of the test force divided by the indentation surface area from providers, and their calculated as follows: the HV = F / (d ½ / 2) ²
Where: HV - Vickers hardness symbols, N/mm2 (MPa);
F - Test force, N;
d - the indentation diagonal arithmetic average, mm.
Vickers hardness test force F 5 (49.03) 10 (98.07) 20 (196.1) 30 (294.2) 50 (490.3) 100 (980.7) Kgf (N) and other six level can be measured hardness values range from 5 ~ 1000HV.
Representation example: 640HV30/20, test force with 30Hgf (294.2N) 20S (seconds) determination of the Vickers hardness value of 640N/mm2 (MPa).
Vickers hardness method for the determination of a thin metal material and the surface layer hardness. It has the main advantages of the Brinell, Rockwell, France, and overcome their shortcomings, but not as good as Luo's method is simple. Vickers method is rarely used in the steel pipe standard.
(1) the generic term
① delivery status. Is the final plastic deformation refers to the delivery of products or the status of the final heat treatment. Generally do not heat-treated to delivery of said hot-rolled or cold drawn (rolled) or manufactured state; said heat treatment after heat treatment delivery status, or according to the type of heat treatment that normalized (normalization), quenching and tempering, solution annealing state. When ordering, delivery status specified in the contract.
② According to the actual weight of the delivery or delivery by the theoretical weight.
Delivery of the actual weight - the weight of their products by weighing (weighing) the weight of delivery;
Theoretical weight - the time of delivery, the weight of their products is said that the size calculated from the weight of steel public. The formula is as follows (according to theoretical weight delivery requirements to be specified in the contract):
Steel pipe per meter of the theoretical weight (density of steel for 7.85kg/dm3) formula:
W = 0.02466 (D-S) S
Where: W - steel per meter theory weight, kg / m;
D - steel pipes of nominal outside diameter, mm;
S - steel pipe nominal wall thickness, mm.
③ guarantee conditions. Tested according to the provisions of the current standards projects and ensure that the provisions of the standard, called the warranty conditions. To ensure that conditions are divided into:
A basic guarantee for the condition (also known as a necessary condition). Regardless of whether the customer specified in the contract. Need to be carried out in accordance with the standard provisions of the survey, and to ensure that test results meet the standard requirements. Process performance, such as chemical composition, mechanical properties, dimensional deviation and surface quality, as well as crack detection, hydrostatic test, or flattening or flaring and other experiments are a necessary condition.