Seamless carbon steel pipe hardness test method

The hardness test is to slowly press a hard indenter into the surface of the carbon seamless steel tube under specified conditions, and then use the depth or size of the test indentation to determine the hardness of the material. Hardness test is a simple, fast and easy-to-implement method in material mechanical property test.

Inner diameter of seamless steel pipe is more than 6.0mm and wall thickness is less than 13mm annealed seamless steel pipe material, which can be used W-B75 Webster Hardness test with very fast, easy, suitable for rapid non-destructive of the seamless steel pipe material qualified inspection. Inner diameter of seamless steel pipe is greater than 30mm and wall thickness greater than 1.2mm seamless steel tubes, using a Rockwell hardness test HRB, HRC hardness.

Inner diameter of seamless steel pipe is greater than 30mm, wall thickness less than 1.2mm of seamless steel tubes, Rockwell superficial hardness test hardness of HRT or HRN. Diameter less than 0mm, more than 4.8mm of seamless steel pipe, pipe dedicated Rockwell hardness test HR15T hardness. When the seamless steel pipe inner diameter greater than 26mm, you can also use the Rockwell or the Rockwell superficial hardness test hardness of the pipe wall.

The tensile test uses carbon steel pipes made of samples, sample in the tensile test machine will pull to fracture, then the determination of one or several mechanical properties, usually only the determination of tensile strength, yield strength, percentage elongation and section shrinkage. The tensile test the mechanical properties of metal materials, the basic test methods, almost all metallic materials, as long as the mechanical properties required to provide a tensile test. Especially those who shape is not easy material hardness test, tensile test to become only the mechanical properties testing means. The hardness test is a hard indenter prescribed conditions slowly pressed into the surface of the sample, and then test the indentation depth or size, in order to determine the size of the material hardness. The hardness test is the mechanical performance test with the easiest, fastest and most easy to implement. Hardness test is non-destructive, the approximate conversion relationship between hardness and tensile strength values. The material’s hardness value can be converted into the tensile strength values, it has great practical significance.

Tensile test is not easy to test the strength is very convenient, so people are increasingly test hardness and less test its strength, and hardness conversion. Hardness manufacturing technology continues to progress and innovation, the original can not directly test the hardness of materials, such as seamless steel pipe, stainless steel plate and stainless steel bands, now may directly test the hardness of the Therefore, there is a hardness test is gradually replaced by the trend of the tensile test. The hardness test of the stainless steel to take into account its mechanical properties, performance and quality of this is related to the deformation of stainless steel as raw materials, stamping, cutting and other processing. Therefore, all seamless steel tubes for mechanical properties testing. Mechanical properties of the test method is mainly divided into two categories, a tensile test, hardness test.

Most of which are national standards in stainless steel also provides the tensile test and hardness test. For those not easy for hardness testing of materials, such as seamless steel pipe only requires that the tensile test. Stainless steel standard, general provisions of the cloth, Luo, Victoria three hardness test method, determination of the HB, HRB (HRC) and the HV hardness value, the provisions of the three hardness values ​​only for one can be. Especially the newly developed portable superficial Rockwell hardness tester, pipe Rockwell hardness tester can be as thin as 0.05mm stainless steel plate, stainless steel with a thin to 4.8mm seamless steel tubes for fast, accurate hardness testing, making difficult to resolve domestic problems solved.

Brinell hardness (HB) with a certain diameter of the steel balls or tungsten carbide balls, pressed into the pattern surface of a predetermined test force (F), after the predetermined hold time after drop test force, the diameter of the measurement sample surface indentation (L).

Brinell hardness test force divided by the the indentation spherical surface area quotient. To HBS (Ball Ball Ball Ball) the unit N/mm2 (MPa). The formula is: where: F – pressed into the metal surface of the sample test force, N; D – test steel ball diameter, mm; d – indentation average diameter mm.

Brinell hardness was measured more accurate and reliable, but generally HBS only applies 450N/mm2 (MPa) or less of a metal material, for the harder steel, or thin sheet NA. Steel standards, Brinell hardness is the most widely used, and often said that the hardness of the material, the indentation diameter d both intuitive and convenient.

Brinell hardness is the most widely used methods in carbon steel pipe hardness testing . This method uses the earliest, due to its imprint, and thus the hardness values ​​affected by the sample organization microsegregation ingredients uneven minimal impact, test results points sprinkle a small degree, good reproducibility, can objectively reflect the objective hardness of the material. 

Principle: In a predetermined detection force, a certain diameter of the steel ball is pressed into the specimen surface to maintain a certain time, and then removing the detected force, the pressure imprint diameter measurement on the specimen surface, can be calculated based on the diameter of the pressure imprint pressure marks the gravure area.

Brinell hardness test force divided by the the indentation spherical surface area quotient. Unit 9.807N/mm. The indentation Big steel ball pressed into the deep, low hardness values​​; vice versa hardness values ​​to engage.