Black Seamless Nipple

The quality inspection standards for Black Seamless Nipples cover multiple aspects,and the following are some common standards:

Appearance inspection

Surface defects:According to relevant standards such as GB/T 12459"Steel Welded Seamless Pipe Fittings",the surface of Black Seamless Nipples should be smooth,without defects such as cracks,folds,double skin,missing flesh,burrs,etc.The depth of minor scratches,dents,and other defects is usually strictly limited,generally not exceeding a certain proportion of the wall thickness,such as 10%.

Color and hue:If there are surface treatment requirements,such as blackening,galvanizing,etc.,the color should be uniform and consistent,without obvious color difference,missing plating,or other phenomena.Taking blackening treatment as an example,the surface should present a uniform black color without obvious redness or discoloration.

dimensional accuracy

Outer diameter and wall thickness:According to standards such as GB/T 8163"Seamless Steel Tubes for Fluid Transport",the outer diameter and wall thickness of Black Seamless Nipples should be within the specified tolerance range.For example,for a Black Seamless Nipple with a nominal outer diameter of 108mm,the allowable deviation for the outer diameter may be±0.5mm,and the allowable deviation for the wall thickness may be±10%.

Length:The length dimension should meet the design requirements,and the allowable deviation is generally within±5mm or±10mm,depending on different specifications and usage requirements.

Thread size:If it is a threaded joint,the thread profile,pitch,outer diameter,pitch,and other dimensions of the thread should comply with the corresponding thread standards,such as GB/T 7306"55°Sealed Pipe Thread",to ensure the fitting accuracy and sealing performance of the thread.

Material testing

Chemical composition:According to GB/T 222"Allowable Deviation of Chemical Composition of Finished Steel"and corresponding carbon steel material standards,such as Q235,20#steel,etc.,there are clear regulations on the content of carbon,silicon,manganese,sulfur,phosphorus and other elements in Black Seamless Nipples.For example,the carbon content of Q235 steel is generally between 0.14%and 0.22%.

mechanical property

Tensile performance:According to GB/T 228.1"Tensile testing of metallic materials-Part 1:Room temperature test method",the tensile strength,yield strength,elongation and other indicators of Black Seamless Nipples are tested.Taking 20#steel as an example,the tensile strength should generally not be less than 410MPa,and the yield strength should not be less than 245MPa.

Impact performance:According to GB/T 229"Charpy Pendulum Impact Test Method for Metallic Materials",impact tests are conducted at specified temperatures(such as room temperature 20℃or low temperature-20℃,etc.)to determine the impact absorption energy and evaluate the toughness of the material.

Hardness:Rockwell hardness tester,Brinell hardness tester,etc.are used to test the hardness of Black Seamless Nipples according to standards such as GB/T 230.1"Metallic Materials Rockwell Hardness Test Part 1:Test Method"and GB/T 231.1"Metallic Materials Brinell Hardness Test Part 1:Test Method".Carbon steel joints of different materials and specifications have corresponding hardness range requirements.

Internal quality inspection

Non destructive testing

Ultrasonic testing:According to standards such as GB/T 11345"Non destructive Testing of Welds-Ultrasonic Testing Techniques,Testing Grades and Evaluation",ultrasonic testing is used to detect whether there are cracks,pores,slag inclusions and other defects inside Black Seamless Nipples.The detection sensitivity and evaluation grade are clearly defined.

Radiographic testing:According to standards such as GB/T 3323"Radiography of Metal Fusion Welded Joints",Black Seamless Nipples are subjected to X-ray or gamma ray penetrations to observe internal defects,and qualitative and quantitative analysis of defects is carried out based on the images on the film.

Metallographic analysis:According to standards such as GB/T 13298"Method for examination of microstructure of metals",perform metallographic analysis on Black Seamless Nipples,observe their metallographic structure,such as grain size,pearlite content,and the presence of banded structure,to evaluate the heat treatment state and quality of the material.

Sealing test

Hydrostatic test:Following standards such as GB/T 13927"Industrial Valve Pressure Test",fill the Black Seamless Nipple with water,apply a certain test pressure,such as 1.5 times the working pressure,and maintain it for a specified time(such as 5 minutes)to observe whether there is any leakage on the surface of the joint.

Pressure test:According to relevant standards,the Black Seamless Nipple is filled with compressed air or other gas,and the specified pressure is applied.The surface of the joint is checked for any bubble leakage using soap water or other methods to determine its sealing performance.