because the initial temperature of the surface layer is lower than that of the heart and the shrinkage is greater than that of the heart

Small longitudinal crackUnder the action of thermal stress, the heart is pulled. At the end of cooling, because the final cooling volume shrinkage of the heart cannot be carried out freely, the surface layer is compressed and the heart is pulled. That is, under the action of thermal stress, the surface of the workpiece is finally compressed and the center is pulled. This phenomenon is affected by factors such as cooling rate, material composition and heat treatment process. The faster the cooling rate, the higher the carbon content and alloy composition, the greater the uneven plastic deformation caused by thermal stress during cooling, and the greater the final residual stress. On the other hand, due to the change of microstructure during heat treatment, the increase of specific volume will be accompanied by the expansion of workpiece volume, and each part of workpiece will undergo phase transformation successively, resulting in inconsistent volume growth and structural stress. The final result of the change of tissue stress is the tensile stress on the surface and the compressive stress in the center, which is just opposite to the thermal stress. The microstructure stress is related to the cooling rate, shape and chemical composition of the workpiece in the martensitic transformation zone.Roselle,Packaging: Welding nets are generally packaged in paper (mostly gray white, yellow, etc.), some similar to welding wire diameter welding nets, agriculture, construction, transportation,RoselleHot dip galvanized welded pipe manufacturer, mining and other industries. Such as machine shields, animal fences flower and tree fences, aisle fences, poultry cages, baskets and decorations.At the same height, light I-beam has narrower legs, thinner waist and lighter weight than ordinary I-beam. No. - is large I-beam, and No. - is medium I-beam. Imported I-beam shall be marked with actual specifications, dimensions and relevant standards.Su Mei,I-beam is mainly divided into ordinary I-beam, light I-beam and wide flange I-beam. According to the height ratio of flange to web, it is divided into wide, that is, the corresponding height is -. At the same height the light I-beam has narrow flange,RoselleHow much is welded pipe per ton now, thin web and light weight. Wide flange I-beam, also known as H-beam, is characterized by two parallel legs and no inclination on the inner side of the legs. It belongs to economic section steel and is rolled on four high universal mill, so it is also called 'universal I-beam'. Ordinary I-beam and light I-beam have formed national standards.It can withstand continuous moderate impact and can provide composite plates of various thicknessesKey technical characteristics of alloy pipe:

Determined by the shape, the section modulus, moment of inertia and corresponding strength of I-beam are obviously better than those of ordinary I-beam with the same single weight. When used in metal structures with different requirements, it shows its superior performance in bearing bending moment, pressure load and eccentric load. Compared with ordinary I-beam, it can greatly improve the bearing capacity and save metal by % ~ %.There are many processes in the process of welded pipe processing, and every detail needs our attention. Welded pipes need to be treated by various processes before application. Heat treatment of welded steel pipe is an important link in the process of welding steel pipe. Hot working is a metal hot working process in which metal materials are heated, insulated and cooled in a certain medium, and the metal properties are controlled by changing the metallographic structure on the surface or inside of the material.The finished product has smooth surface, low friction coefficient, flatness error + / - mm / m length, wear resistance and maximum temperature of ℃Let's see→ I-beam can be processed into T-beam, and honeycomb beam can be combined to form various section forms, which greatly meets the needs of engineering design and manufacturing.After determining the reasonable pickling agent and polishing solution, it is very easy to carry out hot galvanizing for relevant alloy pipes. Use 'phosphating treatment' to degrease the pipes of electrolytic machine equipment put them into the aqueous solution with zinc salt after pickling and passivation, connect the negative level of electrolytic machine equipment, and connect the switching power supply, If the current flows from the positive stage to the negative stage,RoselleHow much is a welded pipe meal, a layer of zinc is deposited in the pipe.When we carry out different projects, we must use different raw materials, which can ensure the quality of the project. In many kinds of data, alloy pipe is widely used. In many projects, we will apply it, so it is very popular in the field. When people carry out the construction of alloy pipe project, there are many things that must be paid special attention to. Let&#;s take you to know:

Methods of exerting efficiency in application of C-section steelMarketing Department,Defects of alloy pipe and solutions: China is a big steel country.After determining the reasonable pickling agent and polishing solution, it is very easy to carry out hot galvanizing for relevant alloy pipes. Use 'phosphating treatment' to degrease the pipes of electrolytic machine equipment, put them into the aqueous solution with zinc salt after pickling and passivation, connect the negative level of electrolytic machine equipment, put them into the cold-rolled steel plate in the direction corresponding to the pipes, and connect the switching power supply, If the current flows from the positive stage to the negative stage, a layer of zinc is deposited in the pipe.Roselle,Advantages of using I-beam: reduce maintenance cost, reduce downtime, improve equipment operation rate, reduce wear, reduce equipment capacity and increase power consumptionGenerally, there are many passivation methods for alloy tubes