Common knowledge of steel pipe
Common knowledge of steel pipe
Classification by production method: Process classification-arc welded pipe, resistance welded pipe, (high frequency, low frequency) gas welded pipe, furnace welded pipe.
Generally, straight seam welding is used for small diameters, and spiral welding is used for large diameters.
1. Welded steel pipe for low pressure fluid transportation (GB/T3092-1993) is also called general welded pipe, commonly known as clarinet.
•The thickness of steel pipe joints is divided into ordinary steel pipe and thick steel pipe;
•The connection end type is divided into unthreaded steel pipe (smooth pipe) and threaded steel pipe.
• The specifications of steel pipes are expressed by the nominal diameter (mm), which is an approximate value of the inner diameter. It is customary to express in inches, such as 11/2 , etc.
• In addition to the direct use of welded steel pipes for low-pressure fluid transportation, it is also used as the original pipe of galvanized welded steel pipes for low-pressure fluid transportation.
• Galvanized welded steel pipe for low pressure fluid transportation (GB/T3091-1993) is also called galvanized welded steel pipe, commonly known as white pipe.
• The wall thickness of steel pipe is divided into ordinary galvanized steel pipe and thick galvanized steel pipe;
•The connection end is divided into galvanized steel pipe without thread and galvanized steel pipe with thread.
• The specifications of steel pipes are expressed by the nominal diameter (mm), which is an approximate value of the inner diameter. It is customary to express in inches, such as 11/2 , etc.
2. Ordinary carbon steel wire casing (GB3640-88) is a steel pipe used to protect wires in electrical installation projects such as industrial and civil construction and installation of machinery and equipment.
3. Straight seam electric welded steel pipe (YB242-63) is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Usually divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe and so on.
4. Spiral seam submerged arc welded steel pipe (SY5036-83) for pressure-bearing fluid transportation is made of hot-rolled steel strip coils, which are spirally formed at regular temperatures and welded by double-sided submerged arc welding. They are used for pressure-bearing fluid transportation. Spiral seam steel pipe. The steel pipe has a large diameter, high transmission efficiency, and can save investment in laying pipelines. Mainly used in pipelines for transporting oil and natural gas.
5. Spiral seam high-frequency welded steel pipes for pressure-bearing fluid transportation (SY5038-83) are hot-rolled steel strips as tube blanks, which are spirally formed at regular temperatures and welded by high-frequency lap welding. They are used for pressure-bearing fluid transportation. The spiral seam high frequency welded steel pipe. The steel pipe has a large diameter, high transmission efficiency, and can save investment in laying pipelines. Mainly used to lay pipelines for transporting oil and natural gas.
6. Spiral seam submerged arc welded steel pipe (SY5037-83) for general low-pressure fluid transportation is made of hot-rolled steel strip coils as tube blanks, which are often spirally formed by double-sided automatic submerged arc welding or single-sided welding. Submerged arc welded steel pipes for general low pressure fluid transportation such as water, gas, air and steam.
7. Spiral seam high-frequency welded steel pipe for general low-pressure fluid transportation (SY5039-83) is a hot-rolled steel strip as a tube blank, which is often spirally formed at temperature, and is welded by high-frequency lap welding for the spiral for general low-pressure fluid transportation. Seam high-frequency welded steel pipe.
8. Spiral welded steel pipe for piles (SY5040-83) is made of hot-rolled steel strip coils as tube blanks, which are often spirally formed by double-sided submerged arc welding or high-frequency welding. They are used in civil construction structures, wharfs, and bridges. Steel pipes for foundation piles.
9. Divided by purpose: product standard, product inspection standard, raw material standard
10. The main content of the product standard includes the following:
Scope of application
Size, shape and weight (specification, deviation, length, curvature, ovality, delivery weight, marking)
skills requirement:
(Chemical composition, delivery status, mechanical properties, surface quality, etc.)
Test methods, inspection rules , packaging,
Marking: There shall be spray printing, stamping, roll printing, steel stamping or pasting mark on the end of each steel pipe. The marking shall include the steel grade, product specification, product standard number, and supplier’s logo or registered trademark for each bundle packaged There should be no less than 2 signs on the bundle of steel pipes (each bundle should be the same batch number), and the signs should indicate: supplier’s trademark, steel brand, furnace number, batch number, contract number, product specifications, product standards, and weight , Root number, manufacturing date, etc.
Quality certificate:
The delivered steel pipe must have a certificate of material conforming to the contract and product standards, contents include:
•Supplier’s name or imprint
•Name of the buyer
•Delivery date
•Contract No
•Product standards
• Steel grades
•Oven number, batch number, delivery status, weight (or number of pieces) and number of pieces
•Variety name, specification and quality grade
• Various inspection results specified in the product standard
Common abbreviations
•SMLS: seamless stainless steel pipe
•ERW: electric resistance welding
•EFW: electric-fusion welded
•SAW: submerged arc welding
•SAWL : Longitude
•SAWH: Lateral submerged arc welding
•SS: stainless steel
•P.E.:plain end
•B.E.: Beveled end
•Thread end
•BW: butt welded end
•Cap
•NPT: national pipe thread
Representation of commonly used steel grades
•The representation method of carbon structural steel:
Q+number+quality level+deoxidation method (optional)
Where the number indicates the yield strength
example:
Q235 B 10#, 20#, 08F
The average ratio of steel to carbon.
•Calculation of theoretical weight of steel pipe (only applicable to carbon steel pipe)
(Outer diameter-wall thickness)×wall thickness×0.02466=kg/m
The density of steel is 7.85 g/cm3
The unit of outer diameter and wall thickness: mm.
Note: Outer diameter and diameter are not equivalent concepts.
Common defects of seamless steel pipe
• 1 inner surface defect
•1.1 Inner Fold: Features: straight, spiral, or semi-spiral zigzag defects appear on the inner surface of the steel pipe.
•1.2 Internal scarring: Features: The inner surface of the steel pipe shows scars, which generally do not take root and tend to peel off.
•1.3 Cutting skin: Feature: The inner surface of the steel pipe presents a straight line or intermittent nail-like lifting skin. It mostly appears on the head of the capillary tube and is easy to peel off.
•1.4 Inner straight: Features: There is a straight line scratch with a certain width and depth on the inner surface of the steel pipe.
•1.5 Inner edge: Feature: there is a linear protrusion with a certain width and depth on the inner surface of the steel pipe.
•1.6 Inner bulge: Features: The inner surface of the steel pipe shows regular convexity and the outer surface is not damaged.
•1.7 Draw pits: Features: The inner surface of the steel pipe shows regular or irregular pits and the outer surface is not damaged.
Common defects of seamless steel pipes
• 2 External surface defects
•2.1 Outward Fold: Feature: a spiral layered fold appears on the outer surface of the steel pipe.
•2.2 Layer separation: Features: spiral or block-like delamination and cracks appear on the surface of the steel pipe.
•2.3 External scars: Features: There are scars on the outer surface of the steel pipe.
•2.4 Pocked surface: Feature: The surface of the steel pipe shows uneven pits.
•2.5 Blue line: Feature: the outer surface of the steel pipe presents a symmetrical or asymmetrical linear rolling mark.
•2.6 Hairline: Feature: On the outer surface of the steel pipe, there are continuous or discontinuous hair-like fine lines.
•2.7 Net-like cracks: Feature: There are band-shaped and large-pitch fish-scale small cracks on the outer surface of the steel pipe.
•2.8 Scratches: Features: The outer surface of the steel pipe is spiral or straight groove-like defects, most of which can be seen at the bottom of the groove.
•2.9 Collision: Features: The outer surface of the steel pipe is concave and convex, and the wall thickness of the steel pipe is not damaged.
• 2.10 Bumps: Features: Irregular scars are produced on the outer surface of the steel pipe due to collision.
•2.11 Correcting concave: Feature: the outer surface of the steel pipe is a spiral concave.
•2.12 Rolling: Features: The wall of the steel pipe shows a concave and convex wrinkle along the longitudinal direction, and the outer surface is concave in a strip.
•2.13 Tear-cracking: Features: the surface of the steel pipe has a cracking phenomenon, which is mostly caused in thin-walled pipe
Common defects of seamless steel pipes
• 3 size tolerance
•3.1 The feature of uneven wall thickness: the steel pipe has uneven wall thickness on the same section, and the maximum wall thickness and the minimum wall thickness are quite different.
•3.2 Wall thickness out-of-tolerance feature: the steel pipe wall thickness is one-way out-of-tolerance. Those with over-positive deviations are called ultra-thick; those with ultra-negative deviations are called ultra-thin.
•3.3 Out-of-diameter out-of-tolerance feature: the outer diameter of the steel pipe exceeds the standard.
•3.4 Bending feature: the steel pipe is not straight along the length or the bend in the shape of a goose head at the end of the steel pipe is called "goose head bend".
