New Delivery for Stainless Steel Flue Pipe - Boiler steel tubes and pipes are used for boiler housings and heat exchangers – Zheyi

Boiler steel tubes and pipes, Refers to the two ends of the opening and hollow section, its length and the periphery of the larger steel, according to the production method can be divided into seamless steel tube and welded steel tube, steel tube specifications with external dimensions (such as outer diameter or side length) and wall thickness, its size range is very wide, from a small diameter of the capillary tube to the diameter of a few meters of large caliber pipe. Steel tubes can be used for piping, thermal equipment, machinery industry, petroleum geological exploration, containers, chemical industry and special purposes.

Boiler steel tubes and pipes, Divided seamless steel pipe and welded steel pipe (seam pipe) two categories. According to section shape can be divided into round tube and special-shaped tube, widely used is circular steel tube, but there are a few square, rectangle, semicircle, hexagonal, equilateral triangle, octagonal special-shaped steel tube. For the steel pipe under fluid pressure to carry out hydraulic test to test its pressure capacity and quality, under the specified pressure does not leak, wet or expansion for qualified, some steel pipe according to the standard or the requirements of the side test, flaring test, flattening test.

Boiler Steel Tubes And Pipes, Production Methods

Boiler steel tubes and pipes, is a kind of seamless tube. The manufacturing method is the same as seamless pipe, but there are strict requirements on the type of steel used to manufacture steel pipe. According to the use of temperature is divided into two kinds of general boiler tube and high-pressure boiler tube.

Boiler steel tubes and pipes, the mechanical property is an important index to ensure the final serviceability of steel. It depends on the chemical composition of steel and the heat treatment system. In the steel pipe standard, according to different use requirements, stipulated the tensile properties (tensile strength, yield strength or yield point, elongation) and hardness, toughness indicators, as well as user requirements of high and low temperature performance.

① The general boiler tube temperature is below 350℃, domestic pipe is mainly made of No. 10, no. 20 carbon steel hot rolled pipe or cold drawn pipe.

② High-pressure boiler tubes are often used under high temperature and high pressure conditions. Under the action of high temperature flue gas and water vapor, oxidation and corrosion will occur. The steel pipe is required to have high durable strength, high oxidation corrosion resistance and good microstructure stability

Boiler Steel Tubes And Pipes, Use

(1) General boiler tube is mainly used to manufacture water wall tube, boiling water tube, superheated steam tube, locomotive boiler superheated steam tube, large and small smoke pipe and arch brick pipe.

(2) High pressure boiler tube is mainly used to manufacture superheater tube, reheater tube, pipe, main steam pipe, etc. The supply and demand trend of high-pressure boiler tube industry is generally stable, but the supply and demand situation of each specific sub-industry will be further differentiated. Industry insiders point out that the most critical link is the use and promotion of 20g high-pressure boiler tube equipment for new energy-saving heat preservation.

New energy-saving 20g high-pressure boiler tube products are gradually increasing in the market, such as green environmental protection paint, energy-saving and water-saving bathroom products, environmental protection stone, environmental protection cement foam insulation board, energy-saving and environmental protection products in the broad market of 20g high-pressure boiler tube industry is promising. [1]

The relevant provisions

(1) GB/T5310-2008 “Seamless Steel Tubes for High pressure Boilers” provisions. Chemical composition test method according to GB222-84 and “Method for Chemical Analysis of Iron and Steel and Alloy”, GB223 “Method for chemical analysis of Iron and Steel and Alloy”.

(2) Chemical composition inspection of imported boiler steel pipe shall be carried out according to relevant standards stipulated in the contract

Boiler Steel Tubes And Pipes, The Steel Grade

(1) High quality carbon structural steel steel 20G, 20MnG, 25MnG.

(2) Alloy structure steel 15MoG, 20MoG, 12CrMoG, 15CrMoG, 12Cr2MoG, 12CrMoVG, 12Cr3MoVSiTiB, etc.

(3) Rust heat resistant steel commonly used 1Cr18Ni9, 1Cr18Ni11Nb boiler tube in addition to ensure chemical composition and mechanical properties, to do water pressure test, to make flaring, compression test. Steel tubes are delivered in heat treatment condition.

In addition, the microstructure, grain size and decarburization layer of finished steel tubes are also required

Boiler Steel Tubes And Pipes, Physical Properties Of

(1) GB3087-2008 “Seamless Steel pipe for Low and medium pressure boiler” provisions. Tensile test according to GB/T228-87, hydraulic test according to GB/T241-90, flattening test according to GB/T246-97, flaring test according to GB/T242-97, cold bending test according to GB244-97.

(2) GB5310-2008 “Seamless Steel Tube for high pressure boiler” provisions. Tension test, water pressure test and flattening test are the same as gb3087-82; Impact test according to GB229-94, flaring test according to GB/T242-97, grain size test according to YB/T5148-93; According to GB13298-91 for microstructure inspection, GB224-87 for decarburization layer inspection and GB/T5777-96 for ultrasonic inspection.

(3) Physical properties inspection and indicators of imported boiler tubes shall be carried out according to relevant standards stipulated in the contract.

Boiler Steel Tubes And Pipes, Mechanical Properties Of

Tensile strength
In the tensile process, the maximum force (Fb) of the specimen at fracture is derived from the stress (σ) of the original cross-sectional area (So) of the specimen, which is called the tensile strength (σb), expressed in N/mm2 (MPa). It represents the maximum capacity of a metal material to resist damage under tension. The calculation formula is:

Where: Fb– the maximum force borne by the specimen when it breaks, N (Newton); So– Original cross-sectional area of the sample, mm2.

The yield point
Metal materials with yield phenomenon, the specimen in the process of tensile force does not increase (keep constant) can continue to extend the stress, called the yield point. In case of force decline, upper and lower yield points should be distinguished. The unit of yield point is N/mm2 (MPa).

The upper yield point (σ SU) is the maximum stress before the specimen yields and the force drops for the first time. Lower yield point (σ SL) : the minimum stress in the yield stage when the initial transient effect is not considered.

The yield point can be calculated by:
Where Fs is the yield force (constant) of the specimen during tensile process, N (Newton) So is the original cross-sectional area of the specimen, mm²

Boiler Steel Tubes And Pipes, Elongation After Fracture

In the tensile test, the percentage of the length increased by the standard distance after the specimen is pulled and the length of the original standard distance is called elongation. The unit is %. The calculation formula is:

Where: L1– the distance of the specimen after breaking, mm; L0– Original distance length of sample, mm.

Reduction of section
In tensile test, the percentage of the maximum reduction of the cross-sectional area at the reduced diameter of the specimen after being pulled and the original cross-sectional area is called the area reduction rate. ψ is expressed in %. The calculation formula is as follows:

Where, S0– the original cross-sectional area of the sample, mm2; S1– The minimum cross-sectional area at the reduced diameter of the specimen after breaking, mm2.

Hardness index
Hardness is the ability of a metal material to resist hard objects pressing into a surface. According to the test method and scope of application, hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, micro hardness and high temperature hardness. Commonly used to pipe material have brinell, rockwell, Vickers hardness 3 kinds.

A, Brinell hardness (HB)
A steel ball or carbide ball of a certain diameter is pressed into the sample surface with a specified test force (F), and the test force is removed after a specified holding time to measure the indentation diameter (L) on the sample surface. The Brinell hardness number is the quotient of the test force divided by the surface area of the indentation sphere. Expressed in HBS, the unit is N/mm2 (MPa).

Boiler Steel Tubes And Pipes, Quality And Inspection

Specifications and Appearance

(1) GB3087-2008 “Seamless Steel pipe for Low and medium pressure boiler” provisions. Specifications of steel tubes for various structural boilers, diameters 10 ~ 426mm, 43 kinds in total. There are 29 kinds of wall thickness from 1.5 mm to 26mm. However, the outer diameter and wall thickness of superheated steam pipe, large smoke pipe, small smoke pipe and arch brick pipe used in locomotive boiler are stipulated otherwise.

(2) GB5310-2008 “Seamless Steel Tube for High pressure Boiler” hot rolled pipe diameter 22 ~ 530mm, wall thickness 20 ~ 70mm. Cold drawn (cold rolled) tube diameter 10 ~ 108mm, wall thickness 2.0 ~ 13.0mm.

(3) GB3087-2008 “seamless steel tube for low and medium pressure boiler” and GB5310-95 “Seamless steel tube for high pressure boiler” provisions. Appearance quality: cracks, folding, rolling, scarring, separation and wrinkles are not allowed on the inner and outer surface of the steel pipe. These defects should be eliminated completely. The clearance depth shall not exceed the negative deviation of the nominal wall thickness, and the actual wall thickness at the clearance shall not be less than the minimum allowable wall thickness. [2]

Chemical test

(1) GB3087-2008 “Seamless Steel pipe for Low and medium pressure boiler” provisions. Chemical composition test method according to gb222-84 and GB223 “Methods for chemical Analysis of Steel and Alloy” relevant part.

(2) GB5310-2008 “Seamless Steel Tube for high pressure boiler” provisions. Chemical composition test method according to GB222-84 and “Method for Chemical Analysis of Iron and Steel and Alloy”, GB223 “Method for chemical analysis of Iron and Steel and Alloy”.

(3) Chemical composition inspection of imported boiler steel pipe shall be carried out according to relevant standards stipulated in the contract

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