Cold formed hollow section steel (American Standard) for cold pressed QB square tube (national standard) structure carbon steel cold-formed circular section and pressure welded QB square tube and seamless QB square tube (European standard) non alloy fine grain cold formed welded hollow structural profile (Japanese standard) angle steel QB square tube for general structure galvanized qb square tube for low pressure fluid transmission Standard No.: gbt-. Representative materials: qqbqb， etc. it is mainly used to transport water， gas， air， oil and heating hot water or steam. It is a special product manufacturing enterprise integrating R & D， sales and service. It has long been specialized in selling square tubes，Q355d square tube square tubes，345 galvanized square pipeEffect on seamless square tubes， galvanized square tubes and galvanized tubes. It is used for general low-pressure fluids.
9It must be noted that in the overall process of square tube coating process， the cost of surface treatment is still relatively high， so it is very important to select appropriate treatment. Only by selecting the right treatment can the coating quality of square pipe be well guaranteed.
bB. low alloy structural steel C. ordinary structural steel and high-quality steel for specific purposes (including high-quality steel)
All seamless qb square tubes shall be tested for mechanical properties. Mechanical property tests are mainly divided into two categories: tensile test and hardness test.
ASan IsidroAfter perforation， 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 will be straightened. After straightening， the steel pipe is sent to the gold pipe by belt
GjThe square tube represents the large capacity of the metal material under the action of tension， and the calculation formula is: where: FB -- the strong force borne by the sample when it is broken，Q355d square tube n (Newton); So -- original cross-sectional area of sample， mm. Yield point (& sigma; s) the stress of metal material with yield phenomenon when the specimen can continue to elongate without increasing (keeping constant) the force during the tensile process， which is called the yield point.
When cutting， please fix it with square tubes such as vise， and then cut it after it is fixed.
How to specify the yield point of square tube: if the stress decreases， that is， steel pipe with equal side length. It is made of rolled strip steel after process treatment.
USection shape classification square tube is classified according to section shape: simple section square tube: square tube， 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.
lKThe quality of the solid square tube after the square tube formwork removal and curing can be tested according to the requirements and the following ways: use a magnifying glass to observe whether there are non external force cracks on the structural surface of the solid seamless qb square tube. When non external force cracks appear on the surface of qb square pipe， the crack width on the structural surface of ordinary qb square pipe shall not be greater than .mm.
Square tube has good machinability，Q355d square tube good cold deformation plasticity and weldability; In addition， the toughness of steel does not decrease much during heat treatment，345 galvanized square pipeEffect on but it has quite high strength and wear resistance， especially when water quenching; However， this steel has great resistance to white spots， temper brittleness and overheating during heat treatment.
During 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， resulting in radial plastic deformation and layer damage of square tubes. It is recommended that the stacking layers of smooth pipes refer to apirp l- Recommended Practice for railway transportation of square pipes for pipelines or apirp lw- Recommended Practice for ship and sea vessel transportation of square pipes for pipelines. It can also be determined by test or implemented according to the safe stacking height of square pipes. The stacking layers of pipes shall be implemented according to GBT - polyethylene layer of buried steel pipelines.
Job descriptionjThe purpose of heat is to prevent the generation of cold cracks. Cold crack is directly related to carbon equivalent. Therefore， it is necessary to distinguish the carbon equivalent of the qb square tube， and the carbon equivalent of the qb square tube is the same. If the carbon equivalent of Q is less than .%，Galvanized pipe_ Galvanized square pipe_ Seamless steel pipe_ Square tube - Wuxi Jiahang it can be said that the weldability is OK. Generally speaking， the cold crack increases when the carbon equivalent is .%.
JPrecision inner diameter square tubes for hydraulic and pneumatic cylinders (gb-) are cold drawn or cold-rolled precision square tubes with precision inner diameter for hydraulic and pneumatic cylinders.
Functional index analysis of square tube - commonly used are square tube Brinell angle (HB)， Rockwell angle (HRC) and Vickers angle (HV). Angle is a gauge needle to weigh the soft and hard level of metal data. The angle method is rarely used to determine the internal angle in the current life. It uses the metal data surface tested under the fixed load of the indenter with a certain number and shape to determine its angle value according to the level of the object.
nGalvanized qb square pipe for low pressure fluid transmission， Standard No.: gbt-. The representative material is the same as above. It is mainly used to transport low pressure fluids such as water， gas， air， oil and heating hot water or steam. The surface of square pipe adopts hot galvanizing or cold galvanizing process.
kAThe welding sequence is to reduce deformation. The welding sequence of rectangular butt welding shall adopt layered and symmetrical skip welding from the middle to both sides according to the following principles. The welding deformation is smaller than that of straight through welding， which is conducive to the dispersion and release of stress and avoid complex stress in weldments. During straight through welding， the narrow plastic deformation zone formed at the beginning of welding only occurs once. Moreover， due to continuous welding， the heat input is large， so the shrinkage deformation after welding is very large. In case of layered and segmented skip welding and the plastic deformation area caused by compression is large， the section of each layer is very small， and the heat required is small， and each layer is divided into several sections for skip welding. Each welding section basically re establishes the secondary temperature field on the cold steel plate， and a narrow plastic deformation zone appears each time. Therefore， the average width of the plastic deformation zone (i.e. the size of transverse shrinkage) is smaller than that of the corresponding layered straight through welding， and the longitudinal shrinkage is also smaller， The welding deformation is smaller than that of continuous filling.
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.