Alloy Steel Pipes

Author John Doe
Date Mar 1
Categories Steel Pipe

Materials of alloy steel pipes
Alloy steel pipes have good hardness, which are widely used for pipelines for transporting oil, natural gas, gas, water and certain solid materials. The common alloys are ferroalloys, ferro-chromium alloys, iron-nickel alloys, aluminum alloys(light weights) and copper alloys(good thermal conductivity). The main materials include 16-50Mn, 27SiMn, 20-40Cr, 12-42CrMo, 16Mn, 12Cr1MoV, T91, 27SiMn, 30CrMo, 15CrMo, 20G, Cr9Mo, 10CrMo910, etc. Alloy steel pipes made from 16Mn belong to low alloy steel pipes.

Applications of alloy steel pipes
Alloy steel pipes are mainly used for high-pressure and high temperature pipelines and equipment such as power plants, nuclear power, high-pressure boilers, high temperature superheaters and reheaters.

Three expressions of alloy steel pipe specifications

1. The first one is the outer diameter plus wall thickness. For example, an alloy steel pipe with an outer diameter of 57mm can be indicated by 57x3.

2. The second one is using the inner diameter, that is, the nominal inner diameter. For example, an alloy steel pipe with an outer diameter of 57mm is indicated by DN50.

3. The third one is the inch. For example, an alloy steel pipe with an outer diameter of 57mm can be indicated by 2 inches (1 inch equals to 25.4mm.)

Specific welding steps of alloy steel pipes
Welding processes of alloy steel pipes are heating before welding, quenching and tempering after welding.

Heating
Before welding the alloy steel pipe, it should be heated, and weld it after the temperature is controlled for 30 minutes. The heating and virtual beam temperature tempering of welding are actively operated by the temperature control cabinet for temperature adjustment. Adopt far infrared tracking heat treatment furnace plates. Intelligently and actively set the graph and record the graph, and use the thermal resistance to accurately measure the temperature. The thermal resistance measuring point is from 15mm to 20mm away from the edge of the weld during heating.

Welding methods
1. In order to prevent welding deformation of the alloy steel pipe, each column joint is welded symmetrically by two people, and the welding direction is from the middle to the two sides. After welding one to three layers, reverse planing should be carried out. After the carbon arc gouging is used, the welding equipment needs to be polished. The welding surface should be nitridation treated to show the metal texture and prevent the surface carbonization from causing cracks. The outer hole is welded once, and the remaining inner holes are welded once.

2. When welding alloy steel pipes with two layers, the welding direction should be opposite to that of the layer of alloy steel pipes. The butt welds of each layer are separated by 15 to 20mm.
3. The welding current, welding speed and number of overlapping layers of multiple welding machines should be maintained.
4. In welding, you must start welding from the pilot arc board and finish welding on the pilot arc board. Cut, polish and clean after welding.

Quenching and tempering after welding
After the seam are welded, it should be tempered within 12 hours. If the alloy steel pipe cannot be quenched and tempered immediately, heat preservation and slow cooling should be adopted. When the alloy steel pipe is tempered, temperatures of the two thermal resistances should be measured and the thermal resistance should be welded on both sides of the seam.

Large-Diameter Seamless Steel Pipe Related Details

Author John Doe
Date Mar 1
Categories Steel Pipe

Large-diameter seamless steel pipes can be divided into straight seam arc welded steel pipes and straight seam submerged arc welded steel pipes according to traditional processes. The production process of straight seam welded pipe is simple, low cost, rapid development, and high production efficiency.

First, the steps to explain the large-diameter seamless steel pipe
1. Large-diameter seamless steel pipes are made of a single piece of metal and have no seams on the surface. They are called seamless steel pipes. Seamless steel pipes have hollow sections and are suitable for transporting fluids such as oil, water, and some solid materials.
2. Large-diameter seamless steel pipes are widely used to manufacture structural parts and mechanical parts, such as oil drill pipes, automobile drive shafts, bicycle frames, steel scaffolding, etc. Straight seam steel pipe refers to a steel pipe in which the weld seam is parallel to the longitudinal direction of the steel pipe. When seamless pipes and straight-seam pipes have the same diameter and wall thickness, the pressure and robustness of seamless pipes are much greater than that of straight-seam pipes.
3. Large-diameter seamless steel pipes and welded steel pipes are steel pipes made by crimping steel plates or steel strips.

Second, a complete list of methods for large-diameter seamless steel pipes
1. Seamless steel pipes have much higher corrosion resistance, pressure resistance, and high-temperature resistance than welded steel pipes. When seamless pipes and straight-seam pipes have the same diameter and wall thickness, the pressure and robustness of seamless pipes are much greater than that of straight-seam pipes.
2. Large-diameter seamless steel pipe has a hollow section and is suitable for transporting fluids, such as oil, water, and some solid materials. The production process of straight seam welded pipe is simple, low cost, rapid development, and high production efficiency.
3. Seamless steel pipes have much higher corrosion resistance, pressure resistance, and high-temperature resistance than welded steel pipes. A welded steel pipe is a steel pipe made of steel plates or steel strips pressed together.

Manufacturing method of seamless steel pipe

Author John Doe
Date Jan 26
Categories Steel Pipe

Seamless steel pipe is a kind of long steel with hollow section and no joint around. The seamless steel pipe has hollow section and can be used as the pipeline for conveying fluid, such as oil, natural gas, gas, water and some solid materials. Compared with solid steel such as round steel, seamless steel pipe is lighter in weight when its bending and torsion strength is the same. It is a kind of economic section steel, which is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipe, automobile transmission shaft, bicycle frame and steel scaffold used in construction. Using seamless steel pipe to make annular parts can improve the material utilization rate, simplify the manufacturing process, save materials and working hours, such as rolling bearing rings, Jack sleeves and so on. Steel pipe is also an indispensable material for all kinds of conventional weapons. Gun barrel and barrel should be made of steel pipe.

According to different production methods, it can be divided into hot-rolled pipe, cold-rolled pipe, cold drawn pipe, extruded pipe, etc.

1.Hot rolled seamless steel pipe is usually produced on the automatic pipe mill. After checking and removing the surface defects of the solid tube blank, it is cut into the required length, centring on the end face of the piercing end of the tube blank, and then sent to the heating furnace for heating and piercing on the piercing machine. In the process of piercing, a cavity is gradually formed inside the tube blank under the action of the roller and the plug, which is called the blank tube. Then it is sent to the automatic pipe rolling mill to continue rolling. Finally, the wall thickness is adjusted by the whole machine, and the diameter is calibrated by the sizing machine to meet the specification requirements. It is an advanced method to produce hot rolled seamless steel tube by continuous pipe mill.

2. In order to obtain smaller size and better quality seamless tubes, cold rolling, cold drawing or a combination of both must be used. Cold rolling is usually carried out on a two high mill. The steel tube is rolled in an annular pass composed of a variable cross-section circular groove and a stationary conical plug. Cold drawing is usually carried out on 0.5-100t single chain or double chain cold drawing machines.

3. In extrusion process, the heated tube blank is placed in a closed extrusion cylinder, and the piercing rod and the extrusion rod move together to extrude the extruded part from the smaller die hole. This method can produce small diameter steel pipe.