Inspection methods for hottest metal materials nbs

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Inspection methods for metallic materials nbsp

inspection methods of metal materials

metal materials belong to metallurgical products. The production, ordering, transportation, use, storage and inspection of metal materials must be based on the unified technical standard - metallurgical product standard. The staff engaged in metal materials must master the relevant contents of the standard

the standards used for metallurgical products in China are national standards (code "GB"), ministerial standards (standards of the Ministry of metallurgical industry "Yb", standards of the Ministry of machinery and machinery "JB", etc.) and enterprise standards

I. packaging inspection depends on the type, shape, size, accuracy and corrosion prevention of metal materials

1. Bulk: no packaging, ingots, blocks (not afraid of corrosion, not valuable), large steel (large steel, thick steel plate, rail), pig iron, etc

2. Bundling: refers to small size, corrosion has little impact on use, such as small and medium-sized steel, pipe steel, wire rod, sheet, etc. China is still in the deep development stage of industrialization, informatization, urbanization, marketization and internationalization

3. Box (barrel): refers to corrosion-resistant, small and thin products, such as tinplate, silicon steel sheet, magnesium ingot, etc

4. Shaft forming: finger wire, steel wire rope, steel strand, etc

for products packed in bales and shafts, first check whether the packaging is complete

II. Mark inspection mark is a mark that distinguishes the material and specification of materials, mainly indicating the supplier's name, brand, inspection batch number, specification, size, grade, net weight, etc. Signs are; 1. Coloring: paint the end faces and ends of metal materials with various colors, mainly used for steel, pig iron, non-ferrous raw materials, etc

2. Printing: the method of stamping or painting on the specified parts (end face and end) of metal materials, indicating the brand, specification and standard number of materials. It is mainly used for medium and heavy plates, profiles, non-ferrous materials, etc

3. Listing: metal materials such as bundles, boxes and shafts are listed outside to indicate their brand, size, weight, standard number, supplier, etc

the marks of metal materials should be carefully identified during inspection and properly protected during transportation and storage

III. inspection of specifications and dimensions. Specifications and dimensions refer to the nominal dimensions of the main parts of metal materials (length, width, thickness, diameter, etc.)

1. Nominal size (nominal size): it is the ideal size that people want in production, but it has a certain gap with the actual size

2. Size deviation: the difference between the actual size and the nominal size is called size deviation. Greater than the nominal size is called positive deviation, and less than the nominal size is called negative deviation. Within the specified range of the standard, it is called the allowable deviation. Exceeding the range is called the size out of tolerance. The out of tolerance belongs to unqualified products

3. Accuracy grade: the allowable size deviation of metal materials stipulates several ranges, and is divided into several grades called accuracy grade according to the allowable size deviation. Jinghe launched the first experiment in Dutch waters in June this year, and the grade is divided into ordinary, high, advanced, etc

4. Delivery length (width): it is the main delivery size of metal materials, which refers to the length (width) specification that metal materials should have when they are delivered

5. Normal length (indefinite length): the length is not specified, but must be within a specified length range (according to different varieties, the length is different, according to the Department and factory)

6. Short ruler (narrow ruler): the length is less than the lower limit of the specified general length dimension, but not less than the specified minimum allowable length. For some metal materials, according to the regulations, a part of vulnerable parts 2: Board "short ruler" 7. Fixed length: the length of the delivered metal material must be the length specified by the demander in the order contract (general positive deviation)

8. Multiple length: the length of the delivered metal material must be an integral multiple of the length specified by the demander in the order contract (plus sawing, positive deviation)

in the inspection of specifications and dimensions, attention should be paid to the measurement of material parts and the selection of appropriate measurement tools

IV. quantity inspection. The quantity of metal materials generally refers to the weight (except for individual cases of backing plates and fishplates, which are calculated by the number of pieces). The quantity inspection methods are: 1. Measured by the actual weight: all metal materials measured by the actual weight should generally be weighed and inspected. For solid packages (such as boxes, containers, barrels, etc.), the gross weight, net weight and tare weight shall be indicated on the package. For example, the number of steel sheets, silicon steel sheets and ferroalloys that can be sampled for inspection shall not be less than 5% of a batch. If there is a big difference between the sampling weight and the marked weight, all must be unpacked and weighed

2. Calculate by theoretical conversion: the weight calculated by the nominal size (actual size) and specific gravity of the material can be converted by theory for those shaped plates and other materials with fixed size, but pay attention to the conversion formula and the actual specific gravity of the material when converting

v. surface quality inspection surface quality inspection is mainly the inspection of materials, appearance, shape and surface defects, mainly including: 1. Ovality: the phenomenon that the diameter of metal materials with circular section is different in all directions on the same section. Ovality is expressed by the maximum and minimum diameter difference on the same section, and the standards for different materials are different

2. Bending, bending degree: bending is rolling material. It is a general term that is not straight in the direction of length or width and in the shape of a curve. If their unevenness is expressed in numbers, it is called curvature

3. Torsion: the strip rolling material is twisted into a spiral shape along the longitudinal axis

because the concrete prepared with it has the strength and durability required by the project

4. Sickle bend (side bend): refers to the bending of metal plates, strips and shapes close to the rectangular section along the length (narrow side), with one side showing a concave curve and the other side showing a convex curve, which is called "sickle bend" Expressed in concave height

5. Scoop curvature: refers to the wave phenomenon of ups and downs in the length and width direction of the plate or belt at the same time, forming a scoop shape, which is called scoop curvature. The value indicating the degree of curvature is called the degree of curvature

6. Surface crack: refers to the crack on the surface of metal objects

7. Ears: protrusions extending along the rolling direction due to improper roll matching and other reasons are called ears

8. Entrapment: it refers to that the material surface is in a straight line or arc groove, and the groove bottom can usually be seen

9. Scarring: refers to tongue shaped, fingernail shaped or fish scale shaped thin sheets unevenly distributed on the surface of metal materials

10. Bonding: the mutual adhesion of points, lines, and surfaces between layers of metal plates, foils, and strips during overlapping rolling and annealing. After being lifted, there are bonding traces on the surface, which is called bonding

11. Iron oxide scale: iron oxide scale refers to the metal oxide formed on the surface of materials during heating, rolling and cooling

12. Folding: it is a kind of surface defect formed by metal during hot rolling (or forging). The surface of the bimetallic layer is folded and overlapped in a straight line or curve

13. Pitting: refers to the uneven rough surface of metal materials

14. Subcutaneous bubbles: the surface of metal materials is irregularly distributed, with different sizes and shapes, and the surrounding smooth small bulges, broken bulges are chicken claw shaped cracks or tongue like scars, which are called bubbles

surface defects are mainly caused by improper operations such as production, transportation, loading and unloading, and storage. According to the different impact on the use, some defects are not allowed to exceed the limit at all. Although some defects do not exist, they are not allowed to exceed the limit; Whether or not various surface defects are allowed to exist, or to what extent, are clearly specified in the relevant standards

VI. assurance conditions for internal quality inspection. The inspection basis for the internal quality of metal materials is to adapt to different requirements according to the material, and the assurance conditions are also different. The inspection must be carried out according to the assurance conditions at the time of delivery and acceptance, and meet the requirements. The assurance conditions are divided into points; 1. Basic guarantee conditions: the minimum requirements for material quality, whether proposed or not, must be guaranteed, such as chemical composition, basic mechanical properties, etc

2. Additional guarantee conditions: refers to the items that are inspected according to the requirements specified by the demander in the order contract, and ensure that the inspection results meet the requirements

3. Agreement guarantee conditions: items negotiated by the supplier and the demander and guaranteed in the order contract

4. Conditions for modification: both parties negotiate the inspection items, but only for reference conditions, not for assessment

the internal quality inspection of metal materials mainly includes mechanical properties, physical properties, chemical properties, process properties, chemical composition and internal structure inspection. The first part of mechanical properties and process properties has been introduced. Here, only the principle and simple process of the inspection method of chemical composition and internal organization are briefly introduced

VII. Chemical composition inspection chemical composition is the main factor determining the performance and quality of metal materials. Therefore, the standard stipulates the chemical composition that must be guaranteed for most metal materials, and some even serve as the main quality and variety indicators. Chemical composition can be analyzed and identified by chemical and physical methods. At present, the most widely used methods are chemical analysis and spectral analysis. In addition, spark identification method with simple equipment and fast identification speed is also a practical and simple method for the identification of steel composition

1. Chemical analysis method: determine the composition of metals according to chemical reactions. This method is collectively referred to as chemical analysis method. Chemical analysis methods are divided into qualitative analysis and quantitative analysis. Through qualitative analysis, we can identify which elements the material contains, but we cannot determine their content; Quantitative analysis is used to accurately determine the content of various elements. Quantitative analysis is mainly used in actual production. The methods of quantitative analysis are gravimetric analysis and volumetric analysis

gravimetric method: use appropriate separation means to separate the measured elements in the metal from other components, and then use weighing method to measure the content of elements

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