3PE Coating standard are ANSI/AWWA C104/A21.4 American National Standard for Cement-Mortar Lining for Ductile-Iron Pipe and Fittings for Water, ISO 21809 Petroleum and natural gas industries — External coatings for buried or submerged pipelines used in pipeline transportation systems, DIN 30670 Polyethylen coatings of steel pipes and fittings.

The normal bare pipe will be corroded in the severe environment and its lifetime will be reduced, making the construction and maintenance cost very high. But due to every layer of the 3PE coating system has its good performance, the 3PE coated pipe can protect the pipe in the severe environment and extend its lifetime to 30-50 years even longer. it can significantly reduces the construction and maintainance cost for the pipeline. At the same time, the 3PE coated pipe has favorable thermal insulation property, the thermal losses is just 25% of the traditional pipe, saving a lot of energy cost during operation. At last, the 3PE coated pipe can directly be laid underground or in the water even directly in the frozen earth because of its good anticorrosion property and impact resistance property in the low temperature, no need to construct ditch.

3PE Coating Steel Pipe has good thermal insulation performance, and the heat loss is only 25% of that of traditional pipes. Long-term operation can save a large amount of resources, significantly reduce energy costs, and has strong waterproof and corrosion resistance. With a pipe trench, it can be directly buried in the ground or water. The construction is simple and quick, the overall cost is low, and it has good corrosion resistance and impact resistance under low temperature conditions, and can be directly buried in frozen soil in a certain environment.

According to API5L, GB/T9711.1 pipeline steel pipe performance requirements, according to the different tempering temperature, tempering can be divided into the following:

1. Low temperature tempering (150-250 degrees)

The microstructure obtained by low temperature tempering is tempered martensite. The purpose is to reduce the quenching stress and brittleness of the quenched steel on the premise of maintaining high hardness and high wear resistance, so as to avoid cracking or premature damage during use. It is mainly used for a variety of high carbon cutting tools, measuring tools, API5L,GB/T9711.1 pipeline steel pipe, rolling bearing and carburizing parts, temper hardness is generally HRC58-64.

2.  Moderate tempering (250-500 degrees)

The microstructure obtained by moderate tempering is tempered troxite. The aim is to obtain high yield strength, elastic limit and high toughness. Therefore, it is mainly used for all kinds of API5L,GB/T9711.1 pipeline steel pipe and hot working die treatment, tempered hardness is generally HRC35-50.

3.  High temperature tempering (500-650 degrees)

The microstructure obtained by high temperature tempering is tempered soxite. It is customary to combine quenching and tempering heat treatment called tempering treatment, its purpose is to obtain strength, hardness and plasticity, toughness are better comprehensive mechanical properties. Therefore, it is widely used in automobile, API 5L, GB/T9711.1 pipeline steel pipe, machine tools and other important structural parts, such as connecting rod, bolt, gear and shaft. The hardness after tempering is generally HB200-330.

Mechanical Properties:

1. It is generally suitable for welding of thin steel pipe below 6mm, with the characteristics of beautiful and elegant weld molding and small welding deformation.
2. The maintenance gas is argon with the purity of 99.99%. When the welding current is 50-50A, the argon flow rate is 8-10L/min, and when the current is 50-250A, the argon flow rate is 2-5L/min.
3. The length of the tungsten pole protruding from the gas nozzle is 4-5mm, 2-3mm in the place of poor masking such as fillet welding, 5-6mm in the place of deep grooving, and the interval from the nozzle to the operation generally does not cross 5mm.
4. In order to prevent the appearance of welding pores, it is necessary to clean up the welding parts if there is rust and oil.
5 Welding arc length, welding shallow steel, with 2-4mm is the best, and stainless steel welding, with 3mm is the best, too long maintenance results are not good.
6. When docking the bottom, in order to prevent the back of the bottom weld passage from being oxidized, the back also needs to implement gas maintenance.
7. In order to maintain the welding pool well with argon and facilitate the welding operation, an Angle of 80-85° should be connected between the middle line of the tungsten pole and the workpiece at the welding place, and the general Angle between the filler wire and the workpiece should be as small as possible, generally 0°.
8. Windproof and ventilation. In windy places, please choose the method of retaining the net, and in the room, the appropriate ventilation method should be selected.

In fact, the vessels is a big category among many steel plates, which has very special composition and many excellent properties. At present, this kind of vessels plate is mainly used to make pressure vessels in the market. For different situations and different uses, the corresponding materials to be made are also different.

This kind of device has a relatively large number of brand names in the current market, and its application scope corresponding to different delivery states is also different. In the following small series, users will be specifically introduced about the vessels plate.

Introduction to the use of the vessels

vessels plate is now widely used in petroleum, chemical industry, power stations and boilers, etc. It is used to manufacture reactors, heat exchangers, separators, spherical tanks, oil and gas tanks, liquefied gas tanks and nuclear reactor pressure shells, etc. In addition, this material is also used to manufacture boiler drums, liquefied oil and gas cylinders, high-pressure water pipes of hydropower stations, spiral cases of water turbines and other equipment or components. Moreover, this material has a very broad market at home and abroad.

Introduction of delivery status of vessels

There are four main delivery states of plates, namely quenching, normalizing, annealing and tempering. Moreover, the main application scope of each delivery state is also different.

Main application scope of normalizing

Compared with low carbon steel, the hardness of vessels plate after normalizing is higher than that after annealing, and its toughness is relatively good.

Can be used with medium carbon steel.

Used for tool steel, carburized steel and bearing steel.

Used for steel castings, normalizing, it has a good refining effect on the microstructure of steel materials.

It is used for large forgings and nodular cast iron, which can improve its hardness, strength and wear resistance.

Characteristics of the plate after tempering

1. After tempering, the structural stability of the vessels plate can be improved, so that the size and performance of the workpiece can be kept in a very good state.

2. After tempering, for the product made of vessels plate, it can also eliminate the internal stress in the container plate, thus changing the service performance of the device.

3. The mechanical properties of the vessels plate can be well adjusted, so as to meet the requirements of application in various fields.

Plate is a kind of important steel plate used for manufacturing various boilers and their accessories, and it is also the most widely used and used special steel plate for pressure vessels in China at present.

The nondestructive testing of steel mainly involves ray testing, ultrasonic testing, magnetic particle testing, penetration testing and eddy current testing.

 1. Radiographic Detection (RT)
X-ray testing refers to the non-destructive testing method that uses X-ray or gamma ray to penetrate the specimen and uses film as the equipment for recording information. This method is the most basic and widely used non-destructive testing method.

2. Ultrasonic Detection (UT)
Ultrasonic testing is suitable for nondestructive testing of metal, nonmetal and composite materials. It can detect the internal defects of the specimen within a wide thickness range. For metal materials, can detect the thickness of 1 ~ 2mm thin wall pipe and plate, can also detect several meters long steel forgings; Moreover, the defect location is more accurate and the detection rate of area defects is higher. High sensitivity, can detect the internal size of the specimen is small defects; And the detection cost is low, the speed is fast, the equipment is light, harmless to the human body and the environment, the field use is more convenient.

3. Magnetic Particle Detection (MT)
Principle of magnetic particle detection is magnetized ferromagnetic material and workpiece, but because of the discontinuity, the magnetic field lines on the surface of the workpiece surface and near local distortion and a leakage magnetic field is generated, adsorption on the surface of the magnetic powder and magnetic marks visible form in the right light visual, showing the location, shape and size of discontinuity.

4. Penetration Testing (PT)
The principle of penetration detection is that after the surface of the part is coated with permeant containing fluorescent dye or colored dye, under the action of capillary, after a period of time, the permeable liquid can penetrate into the surface opening defects; After removing the surface excess penetrant, painted on the parts surface imaging agent again, also, under the action of capillary, imaging agent will attract defects in penetrants, penetrating fluid flow back into the imaging agent, in a certain light (uv light or white light), defect penetrant traces are reality, (yellow-green fluorescence or bright red), Thus, the morphology and distribution of defects are detected.

5. Eddy Current Testing (ET)
Eddy current testing places a coil with alternating current on a metal plate or outside a metal tube under test. At this time, an alternating magnetic field will be generated in and around the coil, resulting in a vortex-like induced alternating current in the specimen, called eddy current. The distribution and size of eddy current are not only related to the shape and size of the coil and the size and frequency of the AC current, but also depend on the conductivity, permeability, shape and size of the specimen, the distance from the coil and whether there are cracks on the surface.