The reliability and operational safety of the final product directly depend 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. The PZPS uses modern control methods to detect even the most minor deviations from the norm.
In metallurgy, both non-destructive and destructive ones are used control methods. Each of them has its own characteristics, advantages and applications. Let's consider the main ones.
Non-destructive testing methods
These methods make it possible to check the quality of products without violating 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. It is based on visual inspection and analysis of the optical properties of the object. It allows you to detect surface defects such as cracks, chips, scratches, corrosion and other damage.
The main principles of the method:
- Visual inspection — A specialist examines with the naked eye or with a magnifying glass, identifying visible defects (scratches, cracks, sinks and corrosion) and assessing the overall condition of the object.
- Lighting applications — changing the lighting angle or using different light sources helps to identify subtle defects that are difficult to see under normal lighting.
- Recording results — all defects found and inspection results are carefully documented in order to later decide whether to repair the defect or reject the product.
Visual inspection is the oldest diagnostic method. It was used by blacksmiths in the Middle Ages, assessing the quality of metal by its brilliance and surface structure.
The advantages of the method:
- simplicity and accessibility;
- does not require complicated equipment;
- allows you to quickly detect visible defects;
- can be used in combination with other methods of non-destructive testing for a more accurate assessment of the condition of the object.
Cons:
- does not detect internal defects;
- depends on the experience and skills of the specialist conducting the examination;
- may be limited by lighting conditions and the accessibility of the object for inspection.
Visual control at the PZPS is carried out by experienced technical control department specialists, promptly identifying defects in tape and workpieces.
Ultrasound 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 reflect off the interfaces between media with different acoustic properties. The ultrasonic converter generates high-frequency vibrations (usually 0.5 to 20 MHz) that are fed into the material. When an ultrasonic wave hits a defect (crack, void, inclusions, etc.), it is reflected back to the sensor. The converter receives the reflected signal, which is then analyzed to determine the presence and location of the defect.
Benefits:
- high sensitivity to minor defects;
- the ability to detect defects at a considerable depth;
- relative simplicity and mobility of equipment;
- does not require special surface preparation of the test object;
- safety for the operator and the environment.
Disadvantages:
- the complexity of interpreting the results in the presence of defects of complex shape or material heterogeneities;
- limited applicability for controlling objects of complex shape or with a very rough surface;
- the need to carefully calibrate equipment and adjust control parameters.
Ultrasound diagnostics is used not only in metallurgy, but also in medicine — the principle of operation of ultrasound is similar to metallographic ultrasound testing.
Magnetic method
It is based on the analysis of the interaction between the external magnetic field and the field of the controlled object. Suitable for analyzing ferromagnetic materials such as iron, nickel, cobalt and their alloys.
How it works:
- Magnetizing 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 object's material.
- The formation of magnetic scattering fields. If there are defects in the material (cracks, inclusions, etc.), magnetic fluxes are distorted, which leads to the formation of magnetic scattering fields above the defects.
- Detection of magnetic scattering fields. Special devices (magnetic flaw detectors) record magnetic scattering fields and convert them into visible or sound signals that can be interpreted by the operator.
- Analysis of results. Based on the data obtained, the operator makes a conclusion about the presence and nature of defects in the controlled object.
Benefits:
- high sensitivity to minor 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.
Disadvantages:
- limited use (only for ferromagnetic materials);
- the difficulty of interpreting the results in the presence of a large number of defects or the complex shape of the object;
- the need to thoroughly prepare the facility for inspection (cleaning it from contaminants, removing residual magnetic particles after previous inspections).
Magnetic methods are used in the railway industry to test axles and wheels for cracks at the production stage.
Destructive testing methods
Unlike non-destructive methods, these methods involve breaking or changing 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 make it possible to accurately assess the strength characteristics of materials.
The main types of tests are:
- For stretching — the sample is stretched until it breaks, which makes it possible to determine the tensile strength, yield strength and relative elongation of the material.
- For compression — used for brittle materials. The sample is compressed until it breaks, which helps determine the compressive strength and other characteristics of the material.
- To bend — the sample is bent until destroyed, which makes it possible to assess the bending strength and other properties of the material.
- For hardness — pressing the indenter into the sample surface makes it possible to determine the hardness of the material on various scales (for example, Brinell, Rockwell, Vickers).
- For impact strength — the sample is subjected to shock load to assess its ability to absorb impact energy and resist destruction.
Benefits:
- 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;
- the possibility of using new alloys for testing.
Disadvantages:
- samples are usually destroyed after testing 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 tensile machines and verified Rockwell and Vickers hardness testers. This makes it possible to quickly and reliably determine the mechanical properties of tape and other products.
Metallographic analysis
It allows you to study the internal microstructure of the metal, identify heterogeneities, 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 treatment. First, the polish 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 form on the surface of the section, which can be seen under a microscope.
Analysis stages:
- Sample preparation. Cutting a section from the analyzed material.
- Polishing. Grinding and polishing the surface of the grinder to obtain a mirror image.
- Pickling. Applying a special reagent to the surface of the section to identify the microstructure.
- Microscopic examination. Study of the surface of the section under a microscope to determine the structure and properties of the material.
- Analysis of results. Interpreting the data obtained and drawing up a conclusion on the properties of the material.
Metallographic analysis makes it possible to identify defects such as pores, cracks, inclusions, structural heterogeneity and other anomalies that may affect the properties of the material. This method is widely used both in metallurgy and in scientific research.
The advantages of the method:
Modern optical microscopes are installed at the PZPS, and studies are carried out by experienced metallographers, which ensures an accurate diagnosis of the quality of steel and precision alloy tapes.
Why do they choose PZPS
The St. Petersburg Precision Alloy 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, 27KH, 50N, 50NP, 79NM, 80NM, 81NMA) — used in transformer engineering, electrical engineering and high-precision electronics;
- precision alloys for elastic elements (40KHNM, 36NHTYU, 17HNGT) — maintain deformation accuracy over a wide temperature range and have excellent resistance to cyclic loads;
- stainless steels (12X18N9, 12X18H10T, 10X17N13M3T) — ideal for aggressive environments, chemical and food industries;
- alloys with high electrical resistance (X15YU5, X23U5, X20N80N etc.) — used in electric heating elements and resistors;
- heat-resistant alloys (HN78T, 20X13) — used in extreme temperature conditions.
Submit a request via form online or call +7 (812) 740-76-57 — we will help you choose the right alloy, prepare a technical opinion and ensure fast delivery!
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