Processing method of stainless steel elbow

by yane Yang Sales Manager

In the piping system, the stainless steel elbow is a pipefitting that changes the direction of the pipe. According to the angle, there are three kinds of most commonly used 45° and 90°180°, and other abnormal angle stainless steel elbows such as 60° are also included according to engineering needs. Stainless steel elbows are made of cast iron, stainless steel, alloy steel, malleable iron, carbon steel, non-ferrous metals and plastics. The way to connect to the pipe is: direct welding (the most common way) flange connection, hot melt connection, fused connection, threaded connection and socket connection. According to the production process, it can be divided into: welded stainless steel elbow, stamped stainless steel elbow, push stainless steel elbow, cast stainless steel elbow, butt weld stainless steel elbow.

What are the main differences between stainless steel elbows and carbon steel elbows?

Stainless steel elbows and carbon steel elbows are mainly made of different materials. The chemical composition of stainless steel elbows will keep the surface of stainless steel elbows from rusting for a long time and will not be corroded. The main difference between stainless steel elbows and carbon steel elbows What is it?
According to the standard production points are as follows:
1. According to the manufacturing standards, it can be divided into national standard, ship standard, electric standard, water standard, American standard, German standard, Japanese standard and Russian standard.
2. Divided by the production method can be divided into push, press, forge, casting and so on.
The 90° stainless steel elbow is mainly used for a connecting pipe in pipe installation for the connection of the pipe bend.
The advantage of the stainless steel elbow is that it is resistant to corrosion. In the case of corrosive chemicals such as chemical papermaking, stainless steel must be used, and the cost is generally high.

The processing method of stainless steel elbow is as follows:

Forging method: The end of the pipe or a section is punched by a swaging machine to reduce the outer diameter. The common forging machine has a rotary type, a link type and a roller type.
Rolling method: Generally, the mandrel is not used, and it is suitable for the inner edge of the thick-walled tube. The core is placed in the tube, and the outer circumference is pressed by a roller for round edge processing.
Stamping method: The pipe end is expanded to the required size and shape with a tapered core on the punching machine.
Bending forming method: There are three methods that are more commonly used. One method is called stretching method, the other method is called pressing method, the third method is roller method, there are 3-4 rollers, two fixed rollers, one adjusting roller, and adjustment. With the fixed roll distance, the finished pipe is curved.
Inflating method: one is to place rubber in the tube, and the upper part is compressed by a punch to make the tube convex and convex; the other method is to form a hydraulic bulge, fill the middle of the tube with liquid, and the liquid pressure drums the tube into the required The shape, the bulk of the production of bellows is used in this way.

Welded stainless steel elbow

The welded stainless steel elbow is called “shrimp bend”, which can be welded after cutting and cutting on the pipe or steel plate, and its specifications can be very large. The number of bends and the bend radius are freely determined by the producer. The welding bend is not very round, and the bending radius of both is not large, generally about 1 times the diameter of the pipe.
The classification method of welded stainless steel elbows can be divided into long-radius stainless steel elbows and short-radius stainless steel elbows according to its radius of curvature. The long radius stainless steel elbow refers to the outer diameter of the tube whose radius of curvature is equal to 1.5 times, that is, R = 1.5D. The short radius stainless steel elbow refers to its radius of curvature equal to the outer diameter of the tube, that is, R = D. D in the formula is the diameter of the stainless steel elbow, and R is the radius of curvature. The most commonly used is the 1.5D stainless steel elbow. If it is not indicated in the contract as 1D or 1.5D, then the 1.5D should be optimized. The most commonly used implementation standards in China are GB/T12459-2005, GB/13401-2005, GB/T10752-1995.

Pressure class classification

If there are about seventeen types according to the pressure level, they are the same as the American pipe standards: Sch5s, Sch10s, Sch10, Sch20, Sch30, Sch40s, STD, Sch40, Sch60, Sch80s, XS;
80, Sch100, Sch120, Sch140, Sch160, XXS, the most commonly used are STD and XS. According to the angle of the stainless steel elbow, there are 45° stainless steel elbows, 90° stainless steel elbows and 180° stainless steel elbows. In this way, there are many types of stainless steel elbows. Orders are often indicated as follows: "LR STD 90° 8", which means long radius, pressure grade STD, 90° 8" stainless steel elbow; , "SR XS 45° 4" means a 4" stainless steel elbow with a short radius and a pressure rating of XS, 45°. The above is the approximate classification of stainless steel elbows. There are two types of tees. The three ports are equal in diameter and have the same diameter tee. The diameters of the two ends are the same, but the diameter of the confluent end is different from the other two diameters. The representation is as follows: For equal-diameter tees, such as "T3" tee, the outer diameter is 3 inches of equal-diameter tee. For the reducer tee, for example, "T4 x 4 x 3.5" means a reducer with a diameter of 3.5 inches and a diameter of 3.5 inches. The pressure rating and the pressure level of the stainless steel elbow are the same, and the specification range is the same.

Stamped stainless steel elbow

Stamping and welding stainless steel elbow, which is stamped into a semi-annular stainless steel elbow with a stamping die of the same material as the pipe, and then two pairs of semi-annular stainless steel elbows are assembled and formed. Due to the different welding standards of various types of pipes, it is usually fixed by semi-finished products by group-to-spot welding. The on-site construction is welded according to the grade of pipe welds. Therefore, it is also called two-semi-welded stainless steel elbows.

Advantages of stamping stainless steel elbows

The stamping process has high production efficiency and is easy to operate, and is easy to realize mechanization and automation. This is because the stamping relies on die and punching equipment to complete the processing, and the number of strokes of the ordinary press is every minute. Up to several dozen times, high-speed pressure can reach hundreds or even thousands of times per minute, and each stamping stroke may get a stamping.
Stamping generally has no chip waste, less material consumption, and no need for other heating equipment, so it is a material-saving, energy-saving processing method, and the cost of stamping parts is low.
Stamping can process parts with large size range and complicated shape, such as stopwatches as small as watches, as large as car longitudinal beams, covering parts, etc., plus the cold deformation hardening effect of materials during stamping, the strength and rigidity of stamping Higher.
Since the die ensures the size and shape accuracy of the stamping part during stamping, and generally does not damage the surface quality of the stamping part, and the life of the die is generally long, the quality of the stamping is stable, the interchangeability is good, and the characteristics are “ exactly the same”. .

The forming process of stamped stainless steel elbows is complicated, and it needs to be welded according to different materials and uses, and gradually formed under a certain pressure. The forming of the stamped stainless steel elbow needs to be carried out according to a certain process, and the corresponding process is strictly followed, otherwise the produced stamped stainless steel elbow will have quality problems. A circular shell can be cut into four 90 ° stainless steel elbows or six 60 ° stainless steel elbows or other stainless steel elbows as needed. This process is suitable for
Any large-scale push-to-stain stainless steel elbow with a stainless steel elbow and a stainless steel elbow with an inner diameter ratio greater than 1.5D is an ideal method for making large stainless steel elbows.
This process molding method is used in the production of different stainless steel elbows, showing good use value in different fields, so that the process has a good value in the production of different stainless steel elbows.

The advantages of the forming process of large-scale stamped stainless steel elbows are mainly reflected in the following aspects:

It is not necessary to use the tube blank as a raw material, which can save the cost of the pipe making equipment and the mold, and can obtain a push stainless steel elbow of any large diameter and relatively thin wall thickness. The raw material of the stamped stainless steel elbow is special, and it is not necessary to add the raw material of the tube blank, and it is easy to control during processing.
The billet of the stamped stainless steel elbow is flat or expandable surface, so the material is simple to cut, the precision is easy to guarantee, the assembly and welding are convenient, the raw materials are easy to control during processing, the operation is relatively simple, there is no complicated process, and the welding and assembly are convenient. .
Due to the above two reasons, the manufacturing cycle can be shortened and the production cost is greatly reduced. Because it does not require any special equipment, it is especially suitable for on-site processing of large stamped stainless steel elbows.

Hot pressed stainless steel elbow
The hot-pressed stainless steel elbow is formed by heating the pipe and then forming it with professional equipment. Then it is cut and heated to a critical temperature. After being kept for a period of time, it is put into the quenching agent quickly, and the temperature is suddenly lowered. The cooling is faster than the critical cooling rate. Method made of stainless steel elbows.

Manufacturing method of hot-pressed stainless steel elbow

The specific production method is as follows: the hot-pressed stainless steel elbow is formed by heating the pipe and then forming it with professional equipment, and then cutting and heating to a critical temperature. After being kept for a period of time, it is quickly put into the quenching agent, and the temperature thereof is suddenly lowered to be greater than the critical value. Stainless steel elbow made by rapid cooling method.
One of the treatment methods: quenching
Quenching is to heat the stainless steel elbow to above the critical temperature, keep it for a period of time, and then put it into the quenching agent quickly, so that its temperature suddenly drops, and it is rapidly cooled at a speed greater than the critical cooling rate, and martensite is obtained. Heat treatment method for unbalanced tissue. Quenching increases the strength and hardness of steel, but reduces its ductility. Quenching agents commonly used in quenching are: water, oil, alkaline water and salt solutions.
Treatment method 2: normalizing
Normalizing is a heat treatment method in which the hot-pressed stainless steel elbow is heated above the critical temperature to convert the hot-pressed stainless steel elbow into uniform austenite and then naturally cooled in the air. Normalizing can eliminate the reticulated cementite in addition to the eutectoid hot-pressed stainless steel elbow. For the hypoeutectoid hot-pressed stainless steel elbow normalizing, the crystal lattice can be refined to improve the comprehensive mechanical properties, and the less demanding stainless steel elbow It is more economical to replace the quenching process with a normalizing fire.

Push stainless steel elbow

Pushing the stainless steel elbow is a push-made stainless steel elbow. Nowadays, the most important type of stainless steel elbow forming production process when the stainless steel elbow is pushed into the shape is firstly because the push-made stainless steel elbow is also The production of stainless steel elbows is fast, and then the stainless steel elbows can be produced in batch production. The quality of the stainless steel elbows is good. The molding process of stainless steel elbows is now stainless steel bending. The process parameters that influence the geometry of the stainless steel elbow are: the material, wall thickness and outer diameter of the billet, the material and shape of the mandrel head, the heating temperature and its distribution, and the advancement speed.
If the actual outer diameter of the tube blank is smaller than the Dp value calculated according to the formula, the bonding performance with the mold is good, but the inner arc of the stainless steel elbow is easily unstable and wrinkled. If the actual outer diameter of the tube blank is larger than the Dp value calculated by the formula, the result is the opposite. According to the above principle, the push tube blank used for the push stainless steel elbow in this test is shown in Table 1 (A is the left part of the elbow).

Stainless steel elbows can be divided into:

According to the manufacturing standards, it can be divided into national standard, ship standard, electric standard, water standard, American standard, German standard, Japanese standard and Russian standard.
Divided by the production method can be divided into push, press, forge, casting and so on.

The 90° stainless steel elbow is mainly used for a connecting pipe in pipe installation for the connection of the pipe bend. Connect two pipes of the same or different diameters to make the pipe turn 90°.
Stainless steel elbow manufacturing process:

1. Feeding: material re-inspection, identification and transfer.
2, cutting: material re-inspection, identification and transfer, size control mark transfer.

First, the material is hot pushed, the pusher is a horn-shaped core or mandrel, the mandrel is thickened and thickened, and the process of pushing the stainless steel elbow is a process of expanding the diameter of the belt, and there is support at the back. The cutting pipe section penetrates the mandrel, and a rear arch frame fixes the mandrel. There is a small car in the middle, and some of the trolleys are hydraulically driven.
Second, in the finishing process, after the shot peening, the scale of the inner and outer surfaces of the stainless steel elbow is removed, and the both ends are treated with a groove to facilitate welding.
Third, we must first select the specifications, and propose the pipe material, for example, a 90-degree stainless steel elbow. Through its curvature, it can be calculated that the long material can be processed into a 90° stainless steel elbow, and then cut with the length as the fixed length.
Fourth, after the push, the stainless steel elbow should be shaped in this hot state, because some stainless steel elbows will be distorted after improper handling, which is not allowed.

3. Inspection: size and appearance quality control.
4, molding: size, appearance control; logo transfer; pressure control. 5A, heat treatment: temperature control. 5B, inspection: hardness, shape and size inspection control. 5C, calibration: shape tolerance control.
6, gold processing: shape size control.
7. Groove inspection: fine groove size control.
8, pickling / passivation: pickling time appearance control.
9, surface treatment: internal appearance control.
10. Non-destructive testing: internal quality control.
11, pickling / passivation: pickling time and appearance control.
12. Logo: Control according to user requirements and standards.
13, finished product inspection: according to the standard for sampling inspection control.
14, packaging.
15. Storage and transportation: Quality control according to specifications and user requirements.

Polishing tips and specific steps for stainless steel elbows:

The first thing that the stainless steel elbow is to be formed is that it is polished. The grinding can make the surface of the stainless steel elbow more bright, and it can also remove some forged corners.

When grinding stainless steel elbows, use 80-mesh louver grinding wheel. Black is better to use. Apprentices recommend using red. It must be slow. Do not press hard. When grinding, try to flatten the grinding machine.
After all the mills have been worn, the 320-mesh louver grinding wheel will be re-grinded once. The 320-head grinding wheel must be polished very carefully, otherwise it will leave the scratch of the 80-mesh grinding wheel.
After the 320-mesh louver grinding wheel has been polished, the stainless steel elbow is waxed, and the new hand is better.
Then continue to polish with the red hemp wheel, then press hard with the force, the harder the better.
After the stainless steel elbow is polished, remember to clean the wax, it is easier to use dust.

How to choose stainless steel elbow?

Stainless steel elbows buy more people and sell more people, but how do people who buy them know stainless steel elbows? Is the quality of the stainless steel elbow you purchased good?

People who buy stainless steel elbows can check whether the material is stainless steel. The chemical composition of the stainless steel elbow will keep the surface of the stainless steel elbow from rusting for a long time and will not be corroded.
The appearance of a good stainless steel elbow is beautiful, the texture performance is strong, you can use the eyes to see if it is smooth, not rough;
Choose a good service to sell stainless steel elbow enterprises, problems can be resolved in a timely manner.

Source: China Stainless Steel Elbows Manufacturer - Yaang Pipe Industry Co., Limited (www.yaang.com)