Localization of gas pressure welding of rebar

The process of rebar welding  was first invented in 1952 for use in the rail transport industry in Japan. With the increase of urban constructions and high-rise construction, attention to retrofitting, more strength and maintaining the life and financial security of people using this type of connection has become important and due to its high safety factor and cost reduction, rebar head welding has become serious. Became the field of housing construction. In this method, instead of the old method of stacking and overlapping the rebar, the two ends of the rebar are connected to each other stronger and safer by applying controlled heat and pressure.

Gas pressure welding method

In the gas pressure welding machine, the rebar is generated by the heat of burning acetylene gas and oxygen at a temperature of about 1200 to 1300 degrees, and at the same time under high pressure by the hydraulic pump, the two rebar ends without changing their molecular structure and mechanical properties. They make a nuclear connection with each other.

Saving and strength

Using this technology, in addition to creating a connection with higher strength and resistance than the overlap method due to the elimination of overlap and also the removal of rebar in construction projects, savings of about 20 to 30% will depend on the type of work and size of rebars.

The method of end-to-end welding of rebars also has a decisive role in the strength of the structure. Due to the reduction of rebar consumption, the weight of the structure is reduced and in proportion to it, the lateral gravitational forces are also reduced, and as a result, the resistance of the structure against earthquakes will increase. Also, due to the reduction of the density of rebars at the connection points, the possibility of better vibration of concrete is provided and in these places, the conflict of concrete with rebars will increase. In addition, in rebar head welding, due to the increase in rebar diameter at the weld point, we see an increase in strength and strength while maintaining the metallurgical properties of the rebar at the connection point.

Experiments

One of the tests performed on rebars welded by this method is the tensile test. This test was performed in reputable laboratories such as Sharif University and Amirkabir University of Science and Technology. In all samples, the failure was from the base rebar and none of the fractures was at the connection point.

Another way to control the quality of welded rebars, which can be easily done even at the project site, is to perform a 90-degree bending test of the welded part of the weld. In this test, there should be no rupture or transverse fracture at the junction of the two rebar surfaces.

Comparison with mechanical rebar connection

Due to the semi-mechanization and non-interference of human parameters during the work and the process, the rebar head welding method has minimal practical defects in the work. Applying pressure while heating the rebars and performing welding as soon as the rebar kneading temperature is reached without the need for operator control is one of the advantages of the ease of working with this method. Also, the absence of a second element in the connection, such as an electrode or mechanical clamp, is another feature of this technology.

In the mechanical connection method, quality control of the second element or the same mechanical clamp in terms of strength of this metal relative to the rebar, control of the same corrosion coefficient of the mechanical clamp and rebar, precision in the same tightening of rebars using crackers and non-destructive control of rebar connection is not possible. And this has led developed countries such as Japan, in addition to the widespread use of this technology in their projects, instead of using overlap methods and mechanical connection with pride to transfer this technology to other countries.

Localization of gas pressure welding of technology

Occurrence of various problems and difficulties in the construction of concrete structures and understanding the need for this issue in the country's projects, the experts of the Structural Test Steel Engineering Company, with their technical studies, to develop and expand new technologies in the welding industry. Discuss concrete structures in the country.

In this regard, the research and development unit of Structural Test Steel Engineering Company, using its experienced and creative experts in this sector, in 2010, set up its own rebar welding department, as the first Iranian technical and engineering company in the field.

Utilizing experts with experience in the fields of civil engineering, metallurgy, and with tact and knowledge of the problems and difficulties in the housing construction industry, the company began to work in the field of production of new gas pressure welding technology. And made its efforts to achieve this technology towards complete localization in the country

Increasing need of domestic projects for gas pressure welding equipment and high price of foreign equipment and lack of easy access to spare parts and accessories of this machine caused the production and manufacture of Iranian machine with specifications and conditions much better than similar foreign model .

One of the advantages of the company's production device is the desirable quality compared to the reasonable price of the device. Considering the internal components of this device, the required parts and services are provided easily due to the existence of more than eight authorized sales agents throughout the country.

The initial context for the proper implementation and application of a technology in a country requires the correct culture of that technology. The need for accurate and professional work in the field of welding engineering and gas pressure welding of rebar technology in Iran, considering the previous problems in the field of construction of steel structures and the low level of welding performed in city-level buildings.

Unfortunately, the lack of implementation of frameworks and basic do's and don'ts in accordance with international standards in construction projects has led to the quality of welding of steel structures to be implemented and implemented at a low level of international standards.

For gas pressure welding of rebar, if the work is not followed and implemented in a principled and precise manner from the beginning, in the not too distant future, people in this field will enter the labor market who produce the same problems in concrete structures. Which is now gripping people and officials in metal structures.

solution

Due to the localization of this technology in Iran, based on the existing standards and compiled by the technical and professional organization of the country, it is better to give accurate and principled training to users of such devices so that we can use this technology to strengthen structures. Let's not weaken them. Providing accurate engineering services and basic training by experienced engineers in this technology and controlling their qualifications and expertise and having a welding skill card and certificate are very important and vital in the application of this technology.

Fortunately, Structural Test Steel Engineering Company, using its eight-year history in the field of training and holding various courses in various welding topics, has been able to meet part of the construction industry's need for gas pressure welding of rebar technicians and operators.

The need for more cooperation from relevant organizations and agencies such as the Ministry of Roads & Urban Development, Construction Engineering Organization, Building and Housing Research Center, Iran Standards  Organization can accelerate the culture and development of this useful technology in the country.

Note: All material and intellectual rights of the above text belong to the author of the text and the use of part or all of the above text is allowed only by mentioning the source and name of the author. If the above condition is not observed in accordance with the Law on the Protection of the Rights of Authors, Writers and Artists and the Law on the Protection of Literary and Artistic Property Rights and Related Rights, the matter can be pursued and sued through the judicial authorities.