Process flow of square tube drawing: because the size of the die hole of the square tube drawing is smaller than the outer diameter of the tube in front of the drawing, in order to make the front end of the square tube pass through the die hole smoothly, so that the clamp jaw of the drawing trolley can the head of the square tube, it is necessary to sharpen the head of the square tube before drawing. Therefore, the end of the square tube with a fixed length should be heated in the slit heating furnace, It is generally 150 ~ 200mm, and the heating temperature is between 750 ~ 900 ℃ according to different wall thickness. Then use 75 ~ 300kg air hammer to sharpen and grind the head of the square pipe. Generally, the square pipe with diameter less than 22mm can be sharpened by rotary forging hammer or roll forging machine.
Mechanical property is an important index to ensure the end use performance (mechanical property) of square pipe, which depends on the chemical composition and heat treatment of steel. In the steel pipe standard, according to different service requirements, the tensile properties (tensile strength, yield strength or yield point, elongation), hardness and toughness indexes, as well as the high and low temperature properties required by users are specified.
Kiskunfelegyhaza.Section shape classification of large-diameter q355b square tube square tube is classified according to section shape: simple section square tube & mdash& mdash; Square tube, rectangular tube and complex section square tube & mdash& mdash; Flower shaped square pipe, open square pipe, corrugated square pipe, special-shaped square pipe, large-diameter q355b square pipe surface treatment classification square pipe is divided according to surface treatment: hot-dip galvanized square pipe, oil coated square pipe acid pickling square pipe, large-diameter q355b square pipe purpose classification square pipe is classified according to purpose & mdash& mdash; Square tubes for decoration, machine tool equipment, machinery industry, chemical industry, steel structure, shipbuilding, automobile, special purpose, large-diameter q355b square tube wall thickness classification, large-diameter q355b square tube according to wall thickness Classification & mdash& mdash; Super large diameter q355b square pipe, large diameter q355b square pipe and thin-wall large diameter q355b square pipe rectangular pipe are the names of square pipe and Q345B square pipe that is, steel pipe with equal side length. It is made of rolled strip steel after process treatment. Generally, the strip steel is unpacked leveled, crimped and welded to form a round pipe, then rolled into a square pipe from the round pipe, and then cut into the required length. Usually 50 pieces per bag. Q355b square pipe, also known as square and rectangular cold-formed hollow section steel, is referred to as square pipe and rectangular pipe, code f and j respectively. The allowable deviation of wall thickness of q355b square pipe shall not exceed plus or minus 10% of nominal wall thickness when the wall thickness is not greater than 10mm plus or minus 8% of wall thickness when the wall thickness is greater than 10mm, many new substances have taken place, and the original characteristics have changed. However, in order to maintain the original relevant characteristics, anti-oxidation treatment is required. The direct reason is to prevent the square tube from reacting with the oxygen in the air, which is the way to isolate the oxygen in the air. Today, this article makes a relatively standardized treatment on the relevant steps to prevent oxidation of square tubes: the key depends on what kind of antirust paint you use. 1. If you use epoxy zinc rich or iron rich antirust paint, you can directly spray fluorocarbon paint on it; 2 if alkyd antirust or red lead is used, the surface treatment is generally carried out, that is, the scale, rust, dirt and attachments on the surface of the square pipe are removed. Those that cannot be treated by physical treatment should be treated by chemical treatment.
The cutting surface of the square tube shall be true circle, and the cutting line shall be at right angles to the axis of the square tube. Excessive force is the reason for cutting the square tube into flat or oval, so the square tube should be cut with appropriate force.
The flattening speed of the sample can be 20 ~ 50mmin.
The square tube adopts the electric contact pressure gauge to press down the pressure of the oil cylinder on both sides of the conveyor to ensure the smooth transportation of the strip steel.
Hardness hardness is a pointer to measure the hardness and softness of metal materials. At present, the hardness method is commonly used to measure the hardness in production. It uses the indenter with fixed geometry to measure the hardness value of the metal material surface tested under fixed load according to the degree of hardness.
How to specify the yield point of square tube: if the stress decreases, the upper and lower yield points shall be distinguished. The unit of yield point is nmm2 (MPa
demand.The covering shall be strong and durable to prevent decay and leakage caused by long-term sun and rain.
At present, researchers at home and abroad have carried out experimental discussion on the anti adhesion of square tube surface. So far, there is still a lack of research on surface adhesion, there is no systematic and perfect theory to guide the preparation of anti adhesion inner surface of pipeline, and there is a lack of operable and low-cost inner surface preparation technology of square pipe. In terms of solid surface adhesion mechanism, based on the solid-liquid interface adhesion work theory and smooth solid surface model, this paper analyzes the spreading process on machined rough surface, studies the dynamic movement characteristics of solid-liquid vapor phase line, directly analyzes the adhesion process, It provides theoretical guidance for the preparation of anti adhesion surface of pipeline.
Square pipe is the name of square pipe, that is, steel pipe with equal side length. It is made of rolled strip steel after process treatment. Generally, the strip steel is unpacked, leveled, crimped and welded to form a round pipe, then rolled into a square pipe from the round pipe, and then cut into the required length. Usually 50 pieces per bag.
Mechanical properties of seamless q355b square tube: tensile strength & sigma; b (MPa)：≥ 980 yield strength & sigma; s (MPa)：≥ 835 elongation & Delta; 5(%)：≥ 12 reduction of area & psi; (%)：≥ 40 impact absorption energy (impact value) (aku2j): & Ge; 39 the products produced by the more complex technology are exquisite. At present, Fangguan is highly praised by the public in the market. What is important is that there is a good guarantee in terms of quality. Therefore, whether Fangguan can obtain such a high market evaluation depends on the complex technology of Fangguan.
The cost is reasonable.Hot rolled q355b square tube continuous casting slab or blooming slab is used as raw material, heated by stepping heating furnace and descaled by high-pressure water into roughing mill. Roughing material enters finishing mill after head cutting, tail cutting and then computer rolling. After final rolling, it is rolled into straight hair coil through laminar cooling and coiler. The head and tail of straight hair curl are often tongue shaped and fish tail shaped, with poor accuracy of thickness and width, hem, tower shape and so on. The coil weight is heavy and the inner diameter of the steel coil is 690mm.
Derusting grade for the construction process of epoxy, ethylene phenolic and other coatings commonly used for square pipes, the surface of square pipes is generally required to reach near white grade (SA). Practice has proved that almost all oxide scale, rust and other dirt can be removed by using this derusting grade, and the depth of anchor grain can reach 40 ~ 100 & mu; m, which fully meets the requirements of adhesion between layer and square pipe The shot derusting process can meet the technical conditions of near white level (SA) with low operation cost and stable and reliable quality.
In the standard of q355b square tube, most of them specify tensile test and hardness test at the same time. For those materials that are not convenient for hardness test, such as q355b square tube, only tensile test is specified. In particular the new portable surface Rockwell hardness tester and pipe Rockwell hardness tester can quickly and accurately test the hardness of stainless steel plate, stainless steel strip and q355b square tube as thin as 0.05mm, which makes it easy to solve the problems that were difficult to solve in China in the past.
Kiskunfelegyhaza.Square tube is made of steel ingot or solid tube blank through perforation, and then made by hot rolling, cold rolling or cold drawing. Square pipe plays an important role in steel pipe industry.
General square pipes are stacked outdoors, and most of them are buried underground when in use, so they are easy to corrode and rust. In order to ensure the smooth flow of the pipeline, square pipes must have strong corrosion resistance. Once the pipeline is corroded, it will cause oil and gas leakage, which will not only interrupt transportation, but also pollute the environment, and may even lead to fire and cause harm.
One of the steps that are prone to defects in the production of square tubes is heat treatment and the other is tensile treatment. Today we need to know the latter. Maybe some people will have a lot of questions about why square tubes are prone to defects in tensile. Now let's analyze the specific causes of defects.