The existence of a welding arch is provided with the plasma conductivity thanks to which through the arch there passes welding current. In turn, the plasma conductivity is caused by existences of the electrons and ions which are formed of neutral atoms by their ionization. The intensity of the atoms ionization in specific conditions is provided with the size of the energy demanded for ionization of atom (Wi). Therefore, the knowledge of the size Wi and its dependence on concrete features of a welding arch is very important parameter.
The microanalysis of metals.
The microanalysis is often used for the reason establishment of the various details destruction during operation.
The microscopic analysis consists in a research of the metal structure at large increases with the help of the microscope. The observed structure is called a microstructure.
The microanalysis allows you to explain in many cases the reasons of the slots properties change depending on change of the chemical composition and Continue reading →
Impact toughness testing (Part 1).
From the moment of emergence of interest in viscosity of metals numerous and various test methods have been developed for measurement of this major property. Speaking about ability of metals to absorb energy, it is necessary to understand that metals absorb energy gradually. First of all, a certain amount of energy is spent for origin of a crack. Then additional energy for increase or distribution of such crack is required.
Some impact tests with a notch allow the crack propagation energy to be measured Continue reading →
The polymorphic transformations in metals (Part 6).
Like a normal polymorphic transformation, the shear transition begins heterogeneously. The germs appear, apparently, in places where there are corresponding dislocation nodes. The crystals grow rapidly at a speed of> 103m/sec. Since the thermal motions of atoms do not play an important role in the shear transformation, it occurs at a great speed and at temperatures close to absolute zero. The rate of polymorphic transformation is particularly large in a defect-free crystal. If a growing crystal meets a boundary, a sub-boundary, or a cluster of dislocations, growth by a shear is usually stopped: partial dislocations stop at the defect. The violation of the fit (joints) of lattices and the appearance of a normal interphase boundary with the distorted packing of atoms can also occur as Continue reading →
Welder Qualification Test (Part 7).
The sequence of actions for the welder’s certification is included below:
- The main parameters definition;
- The check of suitability of the equipment and materials;
- The check of configuration and provision of the control sample;
- The observation of the welding for check of respect for applicable technology;
- The select, determination and cutting of the necessary control samples;
- The test and assessment of samples;
- The required documentation execution;
- The observation of the production welding works.