What is the harm of the freshly welded gas steel pipe being cooled by splashing water

The freshly welded gas steel pipe is cooled by splashing water, which is easy to deform and crack. Cooling too quickly will cause internal cracks, change the toughness of the steel, and deform. Therefore, structural welding and special steel welding cannot be watered.

Tips: The rapid cooling of the weldment at high temperature will produce cold cracking, which is a prohibited operation in engineering construction, especially for high-temperature and high-pressure weldments. If the operation is based on the optimal welding strength, any welding should be preheated before welding, and heat treated after welding, so that the welding stress can be eliminated during the heat treatment process, and the temperature should be carried out according to the heat treatment curve of each material.

Welding: also known as welding, bonding, is a manufacturing process and technology that joins metals or other thermoplastic materials such as plastics by heating, high temperature or high pressure. Welding achieves the purpose of bonding through the following three ways:

The material becomes hard, loses its toughness, and is prone to breakage.

Water repellent is the quenching process, and the workpiece is cooled in a medium, such as water quenching and oil quenching. The advantages are simple operation, easy to realize mechanization, and wide application.

Pan. The disadvantage is that the quenching stress in water is large, and the workpiece is easy to deform and crack; Quenched in oil, the cooling rate is small, and the diameter is hardened.

Small, large workpieces are not easily hardened.

Water cooling is estimated to produce cracks.

Welcome to pay attention to the welding exchange bar to post on the welding exchange bar.

Welcome to pay attention to the welding exchange.

What material is a gas steel pipe made of?

Welded steel pipes are generally used for public risers for indoor heating. For details, please refer to the "Residential Design Code".

The connection form of welded steel pipe is divided into DN>32mm welding, and DN less than or equal to 32mm wire connection.

Welded steel pipes have the characteristics of simple construction, easy to purchase, and more economical, but there are shortcomings such as rust and decay in use, scaling on the inner wall affected by water quality, reducing the amount of transportation and even blockage, so they should be replaced for a certain number of years to ensure the heating effect.

Heating risers are generally galvanized steel pipes, and welded steel pipes are generally used for underground main pipelines.

Stainless steel is available in several materials, 2 series, 3 series. It is best not to splash water directly on the 4 series to cool, because the water-repellent welds of this material may crack!

Yes, but you have to control it well, not too quickly, or only quench in one direction, otherwise it will be deformed and bent very much.

Resolutely do not allow it, quenching will occur, increase the chance of cracks, and pores will also occur due to the invasion of water. And because water ionizes at high temperature to form hydrogen ions, it is easy to cause intergranular fission and intergranular cracks.

Pressure piping is absolutely not a no-no. Because, the stress increases, and the corrosion resistance becomes worse.

No, it will cause severe contraction and cracking.

The safest way to do this is to use a thermometer to measure the temperature and start cooling it with water after 850-900 degrees.

The purpose of water cooling is to allow the stainless steel to cool rapidly in the temperature range of 850-400 to prevent the sensitization of the stainless steel.

Stainless steel electrodes, often see workers do this, the coating does not need to be knocked, it is directly blown off, and the surface is still bright.

304 stainless steel is an austenitic stainless steel, which is equivalent to 1Cr19Ni9

Austenitic stainless steel has a characteristic: it is austenite when it is above 900 degrees, and it is martensite when it is below 900 degrees to more than 600 degrees, and when the temperature continues to drop, it is transformed into austenite. Cracking of the interface during welding is at the martensitic stage.

Solution: After welding, immediately cool down with water to shorten the time in the martensitic stage. The interface will not crack.

Pipeline welding technology includes two aspects: the positioning method of steel pipes and the welding of large diameter steel pipes. The details are as follows:

1. The combination positioning method of the steel pipe.

The axis of the positioning steel pipe must be aligned to avoid centerline deflection or slope differences. The positioning point is fixed, for the steel pipe with a larger diameter, by using the counterpart to assist the counterpart, in order to meet the welding standard, the problem of positioning weld needs to be carefully checked and dealt with, once the welding defect appears, it is necessary to shovel off the rewelding, and the slag and spatter in the positioning welding need to be thoroughly cleaned up, and the positioning weld is repaired into a welding joint with a gentle slope on both sides.

2. Welding of large diameter steel pipes.

The diameter of gas pipelines is generally greater than 15cm and less than 40cm. The diameter of large diameter steel pipes is usually greater than 40cm. In the welding of large diameter steel pipes, three methods can usually be used: flat welding, vertical welding, and vertical welding.

The annular weld is divided into two symmetrical semicircles, and the welding work is carried out in the order of flat welding, vertical welding and vertical welding, and the arc starting and closing of the steel pipe are located in the position of 1cm in front of the center of the semicircle.

1) Large bottom layer welding.

In order to weld from the bottom layer, we need to use the correct electrode angle and the right speed to control the welding quality. For the welding of the first half of the steel pipe joint, we use an electrode with a diameter of 110 120A. The welding of the second half circle of the steel pipe joint is most likely to produce problems such as collapse, unwelded penetration, bubbles, slag and so on, so it is necessary to grind the two ends of the first half circle of the weld bead into a gentle slope, and a grinding machine can be used, and then it is necessary to grind off 5 10mm at both ends of the beginning and end to ensure the welding quality of the joint.

2) Welding of the filler layer.

Before welding, clean up the welding slag and spatter on the bottom layer. The selection of diameter of the electrode, the use of 120 130A welding current, the use of the middle fast, both sides of the slow transport strip mode, so that the groove is fully fused, in order to avoid improper operation caused by slag inclusion, porosity and other defects, the welding current should be larger, the speed of the transport bar should not be too fast, to ensure that the weld bead layer between the fusion is good, the layer head should be staggered.

3) Welding of the cover layer.

By selecting the electrode diameter of 4 mm and then using a current of 150 160 A, ensure that the welding operation and the filler operation are the same. After completion, it is necessary to ensure the separation of slag and molten iron, and the arc blowing force can be used. It is also necessary to ensure that the weld pool is always in a clear and bright state, and the welding rod is evenly swinged, and the two sides of the cover weld are more than about 2mm compared to the edge of the groove.

The gas pipeline belongs to the pressure pipeline, first of all, the welder must participate in the pressure pipeline welder training, and pass the examination before the dao

You can work with a certificate;

In addition, pipeline welding methods include: manual argon arc welding, electrode arc welding and flux-cored gas shielded welding, etc., which are generally selected according to the pipe diameter.

There are different welding methods for welders are not the same, the operation is currently more used in the vertical downward welding method, when the pipe diameter is small, with manual welding rods; When the pipe diameter is large, the semi-automatic welding method is used.

1. SY 0402-2000 specification for construction and acceptance of oil and gas pipeline crossing projects.

2. SY%t 5922-2003 Natural Gas Pipeline Operation Code 3, SYT 6233-2002 Natural Gas Pipeline Trial Operation and Production Code 4, GB50369-2006 Oil and Gas Long-distance Pipeline Engineering Construction and Acceptance Code.

Lots of standards

1. SY 0402-2000 Code for Construction and Acceptance of Oil and Gas Pipeline Crossing Project 2, SY%t 5922-2003 Code for Operation of Natural Gas Pipeline 3, SYT 6233-2002 Code for Trial Operation and Production of Natural Gas Pipeline 4, GB50369-2006 Code for Construction and Acceptance of Oil and Gas Long-distance Pipeline Engineering.

It is the construction and acceptance specification of field equipment and industrial pipeline welding engineering.

First of all, you have to determine what medium the pipe is, PE or steel pipe, the requirements are different, the detailed requirements are standardized, the brother above has already said.