Steel pipe standards common terms

Steel standards common terms

 

(1) The generic term

 

The ① delivery state

 

Refers to the state of the delivery of the final product the plastic deformation or the final heat treatment. Generally without heat treatment delivery, said hot-rolled or cold drawn (rolled) or manufacturing state; delivery of said heat-treated condition after heat treatment, heat treatment categories that normalizing (normalization), quenched and tempered, solid solution annealing status. When ordering, delivery status indicated in the contract.

 

(2) actual weight delivery or Theoretical Weight

 

Actual weight - the time of delivery, the weight of their products is delivered weighing (weighing) weight;

 

Theoretical weight weight - the time of delivery, the weight of their products on steel Nominal size calculation. Theoretical Weight (requires press, you need to specify in the contract) is calculated as follows:

 

The theoretical weight per meter of the steel pipe (steel the density 7.85kg/dm3) Calculation formula:

 

W = 0.02466 (D-S) S

 

Where: W - steel pipe theoretical weight per meter, kg / m;

 

D - the public of the steel pipe nominal outside diameter, mm;

 

S - steel pipe male nominal wall thickness, mm.

 

 

(3) to ensure that the conditions

 

Inspection and to ensure that the existing provisions of the standard project comply with the provisions of the standard, called the guarantee conditions. The guarantee conditions are divided into:

 

A basic guarantee conditions (also known as a necessary condition). Regardless of whether the customer specified in the contract. Must be in accordance with the standard provisions of the survey, and to ensure that the test results meet the standard requirements.

 

Such as chemical composition, mechanical properties, size deviation, surface quality and testing, hydrostatic test or flattening or flaring process performance experiments are a necessary condition.

 

B, agreement to ensure conditions: standard in addition to the basic guarantee conditions, there was still "according to the buyer's requirements, the buyer and the seller negotiated and in the contract note? Quot;, or when the demand-side requirements ...... should be in the contract note out "; customers, on the standards in basic guarantee conditions The tightened requirements (such as composition, mechanical properties, size deviation, etc.) or increase inspection items (such as steel pipe ovality uneven wall thickness, etc.). above terms and requirements by supply and demand in order both parties signed a supply agreement and specified in the contract. these conditions, also known as a protocol to ensure conditions. protocol guarantees generally fare increase.

 

④ batch

 

"Batch" refers to a test unit standard inspection lot. In terms of the delivery unit group approved, said consignment. When the bulk delivery, a consignment may include several inspection lot; when the delivery volume is small, an inspection lot can be divided into several consignments.

 

The composition of the "batch" usually has the following provisions (see the standard):

 

A, each batch should be of the same grade (steel class), the same furnace (cans), or the same mother, heat number, the same specifications and heat treatment (heat) steel pipe.

 

B, for high-quality carbon steel pipe, fluid pipe, the different furnace (tank) at the same grade, the same specifications and heat treatment (heat) steel pipe.

 

C, welded steel pipes for each batch should be the same grade (Steel-level), the same specifications of steel pipe.

 

To ⑤ quality steel and high quality steel

 

GB/T699-1999 and GB/T3077-1999 standard grades behind with the letter "A", high quality steel, contrary to the general quality steel.

 

High quality steel in the following part or all superior to high-quality steel:

 

A narrow range of ingredients;

 

B, to reduce the harmful elements (such as sulfur, phosphorus, copper) content;

 

C, to ensure higher purity (requiring low content of non-metallic inclusions);

 

D, higher mechanical properties and process performance.

 

⑥ longitudinal and transverse

 

Said longitudinally parallel to the machining direction (ie, the Shun processing direction) by standard; horizontal and vertical machining direction (machining direction, the steel tube axial).

 

Do impact energy experiment, vertical fracture of the specimen vertical machining direction. So called transverse fracture; the transverse specimens fracture parallel to the machining direction longitudinal fracture, it said.

 

(2) steel pipe shape, size terminology

 

① nominal size and actual size

 

A nominal size: the nominal size specified in the standard, users and producers hope to get the ideal size is also stated in the Contract Order size.

 

B, the actual size: is the actual size of the obtained in the production process, the size is often greater than or less than the nominal dimension. This is greater than or less than the nominal size of the phenomenon known as deviation.

 

② deviation and tolerance

 

A, deviation: In the production process, since the actual size is difficult to achieve the nominal size requirements, i.e. often greater than or less than the nominal dimension, so specified in the standard to allow a difference between the actual size and the nominal dimensions. The positive difference is called a positive deviation, the difference is negative is called negative deviation.

 

B, tolerance: the standard set forth in the positive and negative absolute value of the deviation and called tolerance, also called "tolerance zone".

 

Deviation is directional, that is, to "positive" or "negative" indicates; tolerance is not directional, therefore, the deviation value is called "positive tolerance" or "negative tolerance" is called an error.

 

The ③ delivery length

 

Delivery length, also known as the length of user requirements or contract length. Delivery length standard has the following provisions:

 

A, the usual length (also known as random length): Where the length of the standard specifies the length within and fixed length requirements are referred to as the usual length. For example, structural pipe standards: hot-rolled (extrusion, expansion) steel pipe 3000mm ~ 12000mm; cold drawn (rolled) steel pipe is 2000 mm-10500mm.

 

B Length Length: Length Length should be the usual length range, the size of a fixed length of the contract requirements. But the actual operations are cut out absolutely definite length is unlikely, therefore, the standard provides for definite length allowed positive deviation.

 

To structural pipe standard:

 

Production of definite length tube than usual length tube finished product rate decline, producers proposed fare increase is a reasonable request. The enterprises of the fare increases are not consistent, generally the base price on the basis of a 10% fare increase.

 

C, double length: double length should be in the range of usual length, the contract should specify haplotypes length and a total length of multiples (for example 3000mm x 3, namely 3 multiples of 3000mm, a total length of 9000mm). The actual operation, should be on the basis of the total length of plus allowed positive deviation 20mm, plus the length of each of the haplotype Ft cutting margin. Structural tube, for example, require cutting margin: ≤ 159mm to 10mm outside diameter; outside diameter> 159mm of 10 to 15mm.

 

By supply and demand if the standard deviation of multiple lengths and cutting the margin provisions negotiated and specified in the contract. Times longer scale with definite length, will give a significant reduction in production enterprises to bring the rate of finished production enterprises proposed fare increase is reasonable, its rate of increase is basically the same as the rate of increase of definite length.

 

D, the range of length: the range of length in the usual length range, when the length of a fixed range of user requirements which need to be clearly indicated in the contract.

 

For example: usually a length of 3000 ~ 12000mm, Range Length Length 6000 ~ 8000mm or 8000 ~~ 10000mm.

 

Seen, the length of the range is more lenient than the cut to length and double length requirements, but more than the usual length tightened many, and also to bring about the reduction of the rate of finished production enterprises. The so manufacturers proposed fare increase is justified, its rate of increase is usually in the base price on the fare increase by about 4%.

 

④ uneven wall thickness

 

The pipe wall thickness can not throughout the same objective wall thickness ranges phenomenon exists in its cross-sectional and longitudinal tubular body, i.e. the thickness unevenness. In order to control this heterogeneity, uneven wall thickness allows indicators specified in some steel standards, general provisions (after consultation between the execution) does not exceed 80% of the wall thickness tolerance.

 

⑤ ovality

 

Exists in the circular pipe cross section of the outer diameter ranging phenomenon, namely the existence of necessarily mutually perpendicular maximum outer diameter and the smallest outer diameter, the difference between the maximum outer diameter and the smallest outer diameter is ovality (with or without roundness). In order to control the ellipticity some steel standards specified allowable ovality indicators, generally defined as no more than 80% of the diameter tolerance (consultation between).

 

⑥ curvature

 

Pipe in a curved shape in the longitudinal direction, that is called the degree of curvature is shown using the number of its curve degrees. The standard provisions curvature is generally divided into the following two:

 

A partially curved: by the amount of one meter long ruler at the maximum bending of the steel pipe, measuring the chord high (mm) is the local bending degree value in units of mm / m, that the methods, such as 2.5mm / m . The method is also applicable to the bending of the tube end portion.

 

The percentage of B, full-length total curvature: a piece of string from both ends of the tube taut, measuring pipe bend chord high (mm), and translation of length (in meters), is the length of pipe direction the entire length of bending.

 

For example: Pipe length of 8m, maximum chord 30mm, full-length bending the pipe should be:

 

0.03 ÷ 8m × 100% = 0.375%

 

The ⑦ size of tolerance

 

Dimensions of tolerance or called standard size exceeds allowable deviation. "Size" refers to the diameter and wall thickness of the steel pipe. Usually someone the size of the ultra-poor habits called "tolerance outrageous, this is called deviation and tolerance equated imprecise, should be called" deviation outrageous. Deviation here may be "positive" and "negative" rarely appear in the same batch of steel pipe "positive and negative" deviation outrageous phenomenon.

 

(3) chemical analysis terminology

 

The chemical composition of the steel is the relationship between the quality of steel and one of the important factors for end-use performance, is the preparation of steel, even the main basis of the final product heat treatment system. Therefore, the technical requirements of the steel standard parts, often first on the provisions of the applicable grade 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 smelting ingredients

 

The chemical composition specified in the general standard refers to melting ingredients. It is the and steel smelting finished pouring the chemical composition of the medium-term. So as to have a certain representation, i.e. representative of the average composition of the furnace or tank in the specified in the standard sampling method, the molten steel is cast in the mold samples small ingot, on which the planing taken or drill sampling crumbs, according to the predetermined standards method (GB/T223) analysis, the results must conform to the standard range of chemical composition, but also the basis of customer acceptance.

 

The ② finished component

 

The finished ingredient also known as validation of analytical components, drill or planing sampling crumbs from the prescribed method (GB/T222) finished steel, in accordance with the provisions of the standard method (GB/T223) analysis, to chemical composition. There is deviation, the deviation value between the steel in the crystallization and after plastic deformation, due to the nonuniform distribution of the alloy elements in the steel (segregation), thus allowing the finished component and a range of standard ingredients (melting component) should meet the requirements of the GB/T222 .

 

Finished steel components for user departments or quality inspection department (user except as required by) acceptance of the quality of steel used, manufacturers generally do not do product analysis, but should meet the standard requirements to ensure product analysis.

 

(3) Arbitration analysis

 

Because the two laboratories analyze the results of the same samples a significant difference between and beyond the two laboratories allows the analysis of error, or production enterprises with user departments, demand-side and supply-side analysis of the same samples or finished the same batch of steel, there are differences of opinion authority of units (such as the China Iron and Steel Research Institute or a commodity inspection qualified inspection department), by a third party with rich analytical experience and analysis that is called a arbitration analysis. The arbitration shall be final analysis to determine the basis.

 

(4) the mechanical properties of the term

 

The mechanical properties of steel to ensure the steel is an important indicator of the end-use properties (mechanical properties), it depends on the chemical composition of the steel and heat treatment system. Steel standards, depending on the requirements of 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)

 

Sample in the stretching process, in the pull-off bear most strongly (Fb), a sample of the original cross-sectional area (So) of the resultant of the stress (σ), called the tensile strength (σb) in units of N/mm2 (MPa). It indicates the maximum capacity of the metal material under tension resistance to damage. The formula is:

 

Where: Fb - the specimen pulled off the bear most vigorously N (Newton);

 

So - the original specimen cross-sectional area, mm2.

 

② yield point (σs)

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