The reliability and operational safety of the final product directly depends on the quality of metal blanks and products. That is why special attention is paid to the timely detection of defects, both internal and superficial. At PZPS, modern control methods are used that make it possible to detect even the most minor deviations from the norm.
In metallurgy, both non-destructive and destructive control methods. Each of them has its own characteristics, advantages and applications. Let's look at the main ones.
Non-destructive testing methods
These methods allow you to check the quality of products without compromising their integrity, which is especially important when inspecting finished products or expensive workpieces.
Visual-optical method
One of the simplest, but at the same time effective ways to identify surface defects. Based on visual inspection and analysis of the optical properties of the object. Allows you to identify surface defects such as cracks, chips, scratches, corrosion and other damage.
Basic principles of the method:
- Visual inspection — a specialist conducts an inspection with the naked eye or with a magnifying glass, identifying visible defects (scratches, cracks, pitting and corrosion) and assessing the general condition of the object.
- Lighting application — changing the lighting angle or using different light sources helps to identify subtle defects that are difficult to see in normal lighting.
- Recording results — all detected defects and inspection results are carefully documented in order to make a decision on eliminating the defect or rejecting the product in the future.
Visual inspection is the oldest diagnostic method. It was used by blacksmiths in the Middle Ages, assessing the quality of the metal by its shine and surface structure.
Advantages of the method:
- simplicity and accessibility;
- does not require complex equipment;
- allows you to quickly detect visible defects;
- can be used in combination with other non-destructive testing methods to more accurately assess the condition of an object.
Cons:
- does not allow detection of internal defects;
- depends on the experience and skills of the specialist conducting the inspection;
- may be limited by lighting conditions and accessibility of the object for inspection.
At the PZPS, visual inspection is carried out by experienced technical control department specialists, promptly identifying defects in the tape and workpieces.
Ultrasonic method
This is one of the most advanced methods for detecting internal defects in metals.
Working principle:
The method is based on the ability of ultrasonic waves to propagate in materials and be reflected from interfaces between media with different acoustic properties. An ultrasonic transducer generates high-frequency vibrations (typically 0.5 to 20 MHz) that are injected into the material. When an ultrasonic wave encounters a defect (crack, void, inclusion, etc.), it is reflected back to the sensor. The transducer receives the reflected signal, which is then analyzed to determine the presence and location of a defect.
Advantages:
- high sensitivity to small defects;
- the ability to detect defects at significant depths;
- relative simplicity and mobility of equipment;
- does not require special preparation of the surface of the test object;
- safety for the operator and the environment.
Flaws:
- difficulty in interpreting results in the presence of defects of complex shape or material inhomogeneities;
- limited applicability for testing objects with complex shapes or very rough surfaces;
- the need for careful calibration of equipment and adjustment of control parameters.
Ultrasound diagnostics is used not only in metallurgy, but also in medicine - the operating principle of ultrasound is similar to metallographic ultrasonic testing.
Magnetic method
Based on the analysis of the interaction between the external magnetic field and the field of the controlled object. Suitable for the analysis of ferromagnetic materials such as iron, nickel, cobalt and their alloys.
How does this work:
- Magnetization of an object. The object under study is placed in a magnetic field created by a permanent magnet or electromagnet. As a result, magnetic fluxes are generated in the material of the object.
- Formation of magnetic stray fields. If there are defects in the material (cracks, inclusions, etc.), the magnetic fluxes are distorted, which leads to the formation of magnetic stray fields above the defects.
- Detection of stray magnetic fields. Special devices (magnetic flaw detectors) record stray magnetic fields and convert them into visible or audio signals that can be interpreted by the operator.
- Analysis of results. Based on the data obtained, the operator draws a conclusion about the presence and nature of defects in the controlled object.
Advantages:
- high sensitivity to small defects;
- the ability to control objects of complex shape;
- relative simplicity and low cost of equipment;
- does not require special preparation of the object surface.
Flaws:
- limited application (only for ferromagnetic materials);
- difficulty in interpreting results in the presence of a large number of defects or a complex object shape;
- the need for careful preparation of the object for inspection (cleaning of contamination, removal of residual magnetic particles after previous inspections).
Magnetic methods are used in the railway industry to check axles and wheels for cracks during production.
Destructive testing methods
Unlike non-destructive methods, these methods involve destruction or change in the structure of the sample, but provide accurate data on its physical and mechanical properties.
Mechanical tests
They are carried out on specially prepared samples and allow you to accurately assess the strength characteristics of materials.
Main types of tests:
- Tensile - the sample is stretched to failure, which makes it possible to determine the tensile strength, yield strength and relative elongation of the material.
- Compression - used for fragile materials. The sample is compressed to failure, which helps determine the compressive strength and other characteristics of the material.
- Bend — the sample is bent until it fails, which makes it possible to evaluate the flexural strength and other properties of the material.
- For hardness — pressing the indenter into the surface of the sample allows you to determine the hardness of the material on various scales (for example, Brinell, Rockwell, Vickers).
- For impact strength — the sample is subjected to impact loading to evaluate its ability to absorb impact energy and resist destruction.
Advantages:
- high accuracy and reliability of data on the mechanical properties of materials and products;
- the ability to conduct tests at all stages of production, including quality control of raw materials, semi-finished products and finished products;
- Possibility of use for testing new alloys.
Flaws:
- samples after testing are usually destroyed and cannot be reused;
- requires special expensive equipment and highly qualified specialists to conduct tests and interpret the results.
The PZPS uses modern testing equipment, including new breaking machines and Rockwell and Vickers hardness testers. This allows you to quickly and reliably determine the mechanical properties of tape and other products.
Metallographic analysis
Allows you to study the internal microstructure of the metal, identify inhomogeneities, porosity, inclusions and others defects.
The essence of the method is that a small piece (section) is cut out of the test sample, which is then subjected to special processing. First, the section is polished to a mirror finish, then a special reagent is applied to it, which causes selective dissolution of individual components of the material. As a result, depressions and elevations are formed on the surface of the polished section, which can be seen under a microscope.
Analysis steps:
- Sample preparation. Cutting a thin section from the analyzed material.
- Polishing. Grinding and polishing the surface of the section to obtain a mirror reflection.
- Etching. Application of a special reagent to the surface of the polished section to identify the microstructure.
- Microscopic examination. Studying the surface of a polished section under a microscope to determine the structure and properties of the material.
- Analysis of results. Interpretation of the data obtained and drawing a conclusion about the properties of the material.
Metallographic analysis makes it possible to identify defects such as pores, cracks, inclusions, structural inhomogeneity and other anomalies that can affect the properties of the material. This method is widely used both in metallurgy and in scientific research.
Advantages of the method:
Modern optical microscopes are installed at the PZPS, and studies are carried out by experienced metallographers, which ensures accurate diagnosis of the quality of strips made of steels and precision alloys.
Why choose PPPS
The St. Petersburg Precision Alloys Plant is an enterprise with a long history, a strong engineering school and modern quality management. We produce high-precision cold-rolled strip from:
- soft magnetic alloys (49K2FA-VI, 27KKh, 50N, 50NP, 79NM, 80NM, 81NMA) - used in transformer manufacturing, electrical engineering and high-precision electronics;
- precision alloys for elastic elements (40KKhNM, 36NKhTYu, 17KhNGT) - maintain deformation accuracy over a wide temperature range and have excellent resistance to cyclic loads;
- stainless steels (12Kh18N9, 12Kh18N10T, 10Kh17N13M3T) - ideal for aggressive environments, chemical and food industries;
- alloys with high electrical resistance (Kh15Yu5, Kh23Yu5, Kh20N80N etc.) - used in electric heating elements and resistors;
- heat-resistant alloys (KhN78T, 20Kh13) - used in extreme temperature conditions.
Leave a request via form on the website or call +7 (812) 740-76-57 - we will help you choose the right alloy, prepare a technical report and ensure fast delivery!
