Hot rolled qb 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， and there are often defects such as wave shape，Q345B square tube hem，Galvanized square pipe production lineHuge demand for infrastructure investment tower shape and so on. The coil weight is heavy and the inner diameter of the steel coil is mm.
5First， remove the deposits on the surface of the square pipe surface with copper wire brush. Use the perfume oil or other scrubbing oil on the surface layer， or use phosphate or chromate solution， brush， spray or dip coating. After the fixed reaction time， rinse the acid solution with plenty of fresh water on the surface.
uSquare tube， modified square tube， square tube， QB square tube and hot-rolled square tube are qualified in quality inspection. The manufacturer adopts advanced equipment to ensure the quality of each product. Magnetic flux leakage testing for surface defects of square tubes is very similar to magnetic particle testing for square tubes，Q345B square tube and its scope of application， sensitivity and reliability are stronger than magnetic particle testing. Indirect square forming process the traditional forming process of cold-formed square pipe is to gradually roll the hot-rolled steel coil multi stand forming unit into round pipe at room temperature， and then the shaping unit will roll the round pipe into square pipe， which is called indirect square forming process. The traditional roll forming process uses the method of fixed bending point position and variable bending radian to complete the corner forming of pipe blank， which is suitable for rolling small and medium-sized products. Rolling with this process & ldquo; Superb & rdquo; Square tube will show its inherent defects. Because the roll work in the bending process of this process is always concentrated at the point， excessive stress concentration often shows microcracks in the bending process of profiles， which will lead to cracking in serious cases. The products with such defects have serious consequences when they are used in building steel structures. The study of the broken square tube column in the Hanshin earthquake in Japan shows that the corner microcrack is the main cause of the square tube fracture. At the same time， the universality of rolls is limited. The large-size cold-formed square tube used in the process adopts the advanced & ldquo; Direct Square & rdquo; The production process is to directly roll the hot-rolled steel coil into a square and rectangular shape at room temperature.
Stainless steel qb square pipe for mechanical structure， Standard No.: gbt-. Representative material Cr cr crni CrNi crninb etc. It is mainly used for machinery， automobile，Q345B square tube bicycle， furniture，Galvanized square pipe production lineHuge demand for infrastructure investment hotel and restaurant decoration and other mechanical parts and structural parts.
VTombaDuring the storage of square tubes pay attention to the stacking layers of square tubes to avoid local stress at the tube end caused by too many layers， the casting cleaning is not just shot blasting. For large parts， the drum sand cleaning is carried out first， that is the riser of the casting is cut off and rolled in the drum， and the square tubes collide with each other in the drum to remove most of the sand on the surface before shot blasting or shot blasting.
The advantages of real bending are small reverse， accurate forming， and as long as the roll shape is accurate， and the tensile effect will shorten the longitudinal length of the bending line; The metal at the real bend will become thinner due to stretching.
Tensile test is to form seamless qb into a sample，Galvanized pipe_ Galvanized square pipe_ Seamless steel pipe_ Square tube - Wuxi Jiahang pull the sample to fracture on the tensile testing machine， and then measure one or more mechanical properties. Usually， only tensile strength， yield strength， elongation after fracture and reduction of area are measured.
bSpraying (throwing) derusting spraying (throwing) derusting is that the high-power motor drives the spraying (throwing) blade to rotate at high speed， so that the steel sand， steel shot， iron wire section， minerals and other abrasives can be sprayed (thrown) on the surface of the square tube under the action of centrifugal force， which can not only completely remove rust， oxides and dirt， but also the square tube under the violent impact and force of abrasives， It can also achieve the required uniform roughness.
OFirst， remove the deposits on the surface of the square pipe surface with copper wire brush. Use the perfume oil or other scrubbing oil on the surface layer， or use phosphate or chromate solution， brush， spray or dip coating. After the fixed reaction time， rinse the acid solution with plenty of fresh water on the surface.
GLets seeIt is forbidden to degrease the oil square pipes and pipe fittings in the direct production concentration unit， air separation unit， oil refining and chemical engineering according to the design requirements. The purpose of degreasing is to prevent the transported or stored materials from being contaminated by grease or organic matter; Avoid mixing transported or stored materials with grease or organic matter; Oil content to ensure the activity of the catalyst; The content of oil and organic matter to ensure the purity of the product. The installed square pipe shall be disassembled into pipe sections for degreasing. Pipes that cannot be disassembled after installation shall be degreased before installation. Square pipes with obvious oil stains or serious corrosion shall be cleaned by steam purging， sand blasting or other methods before degreasing.
nUThe covering shall be strong and durable to prevent decay and leakage caused by long-term sun and rain.
The painting of the square tube has to go through a process， which requires us to conduct comprehensive consideration and analysis. In particular， the quality and level of the paint and the relevant technical level deserve our attention. Note that the square tube should not be used immediately after painting， but should be placed for a period of time and wait until the paint is dry!
High productivity of square tube: the efficiency of cold production of mechanical parts is very high， especially for parts with large batch. Cold production can be several times， several times or even hundreds of times higher than cutting. For example， the use of cold pin for automobile is twice higher than that of cutting. At present， cold pin automata is used to improve productivity. The productivity of table cooling automata is equivalent to that of ordinary lathes or shaft self-propelled machines.
Energy costsfThe raw material for rolling square tube is round tube blank. For a long time， square tube， rectangular tube， seamless square tube， galvanized square tube and galvanized tube have complete products， excellent quality and favorable price. The round tube embryo shall be cut and processed by cutting machine， and the blank with a growth of about m shall be brought to the furnace for heating. The billet is sent to the furnace for heating at a temperature of about degrees Celsius. The fuel is hydrogen or acetylene. The temperature in the furnace is the key problem. After the round tube billet is discharged from the furnace， it should be pierced through the pressure piercer. Generally， the more common piercer is the conical roll piercer. This piercer has high production efficiency， good product quality large perforation expansion and can wear a variety of steel grades.
UHigh density may not be obtained by simple pressurization， mostly mm and mm. Qb square tube is allowed to deliver short and non fixed length products not less than mm， or in the form of interface tube， but the Demander shall cut off the interface tube when using it. The weight of short length and non fixed length products shall not exceed % of the total delivery. For qb square tube with theoretical weight greater than kgm， it shall not exceed % of the total delivery. The bending degree of qb square tube shall not be greater than mm per meter and the total bending degree shall not be greater than .% of the total length. The square tube is classified according to the production process: hot rolled seamless square tube， seamless square tube and square tube.
cToday， with the development of the world， all fields are coming rapidly， which makes the demand for square tube higher and higher， and the requirements of customers for square tube higher and higher. Now we are studying a new square tube. The following mainly introduces the performance of square tube in tensile strength.
vOPerformance index analysis fatigue of square tube the strength， plasticity and hardness discussed above are the indicators of the mechanical properties of metal under static load. In fact， many machine parts work under cyclic load， under which fatigue will occur.
Both internal and external welding of square pipes are carried out by American Lincoln Electric welding machine for single wire or double wire submerged arc welding， so as to obtain stable welding specifications.