The modification of Ca， rare earth and other trace elements on inclusions changes the structure， morphology and physical properties of inclusions in steel， spheroidize and refine inclusions in steel， so as to improve the mechanical properties of square tubes.
5Formulate the documents stored by the square tube for a long time and implement them in accordance with.
lWhen the vehicle is replaced with seamless square tube blank， the material is too soft to affect the requirements，Large diameter square tube such as warehouses，16Mn hot dip galvanized square pipeThe demand for products is increasing houses and bridges， but it is not suitable for moving components such as wheels. At this time， people often use the plastic theory. The research of the plastic theory can be traced back to . In ， the European Design Association formulated a plastic design code， which is mainly used for static load plane beams and frame structures subjected to bending stress The solution is as follows: for high-rise buildings， more detailed calculations are needed.
MKarmadahMechanical 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，Large diameter square tube yield strength or yield point， elongation)， hardness and toughness indexes， as well as the high and low temperature properties required by users are specified.
UuIt belongs to flaw detector (or hydraulic test) for internal flaw detection. If there are cracks， bubbles and other problems inside the steel pipe， they will be detected. Steel pipes should be strictly selected manually after quality inspection. After the steel pipe is inspected， the number， production batch number， etc. shall be sprayed with paint. And hoisted into the warehouse by crane.
Low alloy steel is divided into q Mn， Q，Large diameter square tube St-， etc.
The advantages of real bending are small reverse，16Mn hot dip galvanized square pipeThe demand for products is increasing accurate forming， and as long as the roll shape is accurate， the R of inner corner forming is more accurate.
hFor transportation: water supply， drainage sewage treatment engineering， mud transportation， marine water transportation.
FOf course， since the qb square tube material is selected as the base metal， it generally has special purposes，Square pipe, square rectangular pipe, seamless square pipe, galvanized square pipe, galvanized pipe - Wuxi Jiahang metal products Co., Ltd so the welding materials will not be selected casually. It is better to use it according to the welding material manual. If the welding rod manual says that the base metal should be preheated， it should be preheated. Because the welding materials are not used according to the manufacturers instructions， the weld performance will be greatly reduced.
HConvenient and efficientThe banding caused by component segregation is difficult to be eliminated by heat treatment. Generally， normalizing can reduce this segregation to a certain extent. Generally， normalizing can correct the segregation to the allowable level. If the banding is serious， which can completely eliminate the strip， but the cost will be very high， which is difficult to achieve for the steel plate due to the surface quality.
wOAfter the sample is flattened to the specified flattening distance h， remove the load and remove the sample.
Material of square tube: q Q (Mn)， #， alloy steel， stainless steel.
Square pipe is a square steel pipe cold drawn from seamless steel pipe， also known as welded pipe and qb square pipe， is a square pipe welded by steel plate or strip steel after crimping. Qb square tube has the advantages of simple production process， high production efficiency， many varieties and specifications and less equipment. The commonly used materials are QA and QC.
Superior qualityoAfter the square tube is cut into a single square tube， the head and root of each batch of square tube shall be subject to strict first inspection. The mechanical properties， chemical composition， fusion condition， surface quality of square tube and NDT shall be carried out to ensure that the pipe making process is qualified before it can be officially put into production.
MSteel used & mdash& mdash; Such as bridge steel， ship steel， boiler steel， pressure vessel steel， agricultural machinery steel， etc.
Compared with other traditional pipes， square pipe supply steel pipe has lighter raw materials， high strength， good resistance， can withstand high internal pressure， sensitive application， and can get used to messy or bad geological conditions.
nAfter perforation， the round tube blank is successively rolled by cross rolling continuous rolling or rolling. Take off the pipe after sizing. The conical drill bit of the sizing machine rotates into the steel embryo at high speed to form a steel pipe. The inner diameter of the steel pipe is determined by the outer diameter length of the sizing machine bit. After sizing， the steel pipe enters the cooling tower for water spray cooling. After cooling， the steel pipe is sent to the gold pipe by belt
kGAll seamless qb square tubes shall be tested for mechanical properties. Mechanical property tests are mainly divided into two categories: tensile test and hardness test.
Large diameter welded square pipe for low pressure fluid transmission， Standard No.: gbt-. Representative material: grade qab. It is mainly used to transport low-pressure fluids such as water， sewage gas， air and heating steam.