steel pressure processing methods
Most of the steel processing and pressure processing, raw steel (billet, ingot, etc.) to produce plastic deformation. Depending on the processing temperature of steel, divided into two kinds of cold and thermal processing. Steel processing methods:
(1) rolling
The metal billet by a pair of rotating roll gap (various shapes), due to compression of the roll material cross-section decreases, the length of the pressure processing method, which is the most common mode of production in the production of steel, mainly used to produce profiles sheet, pipe. Divided into cold-rolled, hot-rolled.
(2) forging
Reciprocating impact or press forging hammer pressure billet change into the required shape and size of a pressure processing methods. Generally divided into free and die forgings used in producing large profiles, cogging cross-section of a larger size materials.
(3) drawing
Rolled metal stock (type, management, products, etc.) through die holes to pull aside into the cross section decreases the length of the processing method is mostly used as a cold.
(4) extrusion
Metal on the closed extrusion Jane, one end to exert pressure, metal extrusion from the provisions of the mold hole and get to have the same shape and size of the finished product processing methods used for the production of non-ferrous materials.
Macroscopic and microscopic examination two steel
A. Steel macroscopic examination
The naked eye or magnifying glass is less than ten times the quality of the steel to be tested, often are the following:
(1) low acid invasion test
Billet or steel sampling by Turning acid erosion, observed the defects of the steel in the different sections, such as shrinkage, porosity, segregation, bubbles, inclusions, etc..
(2) fracture test
The required sample taken after heat treatment, impact break, observation of the fracture, such as checking the "white spots".
(3) tower test
Take a certain length of test bars along the vertical rolling, and then the car into a coarse, fine and three different diameter specimens, to check on the different cross-section of the hairline (fine cracks).
(4) sulfur print
Test ingot or billet commonly used methods: section planed, printed on photo paper, developing, it is evident that the distribution of sulfides in the steel, and steel low defects.
(5) ultrasonic testing
A non-destructive testing, steel internal defects observed by the ultrasonic propagation.
Two. Steel micro-detection
Quality metallurgical microscope examination, usually magnification of 50-100 times, commonly used to check the grain size of steel, decarburized layer, banded structure, network organization, etc., corresponding to these low times to check usually called the high-power test.
mechanical properties of steel commonly used test method
Commonly used test methods are the following:
A tensile testing
Bit stretched specimen in the tensile test machine, you can obtain the following results:
(1) yield point (yield strength)
Under the force of the tensile machine, the sample was bit long, at the beginning of the specimen elongation and tension is proportional to, when the tension after the abolition of the sample still shrink to the size of the original specimen of this deformation is called elastic deformation. The tension continued to increase the sample continue to elongate, but external forces cancellation sample but no longer shrink to its original length, this deformation of income is called plastic deformation. The point of transition from elastic deformation to plastic deformation, called the yield point, its representative symbol is σb units of MPa or N / square millimeter.
(2) tensile strength
In these experiments, when the sample is plastic deformation, the tension continues to increase, the specimen finally pulled off. This time the force is tensile strength, its representative symbol σb units of MPa or N / square millimeter.
(3) Elongation
In these experiments, after the test is to pull off after the originally scheduled gauge was bit long with the original gauge than called elongation, its representative symbol for the τ is, the unit is%.
(4) of section shrinkage (or shrinkage)
The above specimen fractured, measuring the cross-section of the fractured neck shrink with the original basal area ratio, called the section shrinkage, its representative symbol is φ, in units of%.
Bending test
The sample in the state of hot or cold bending, steel bending 90 degrees or 120 degrees, check the steel to withstand bending ability of different steels have different requirements on the bending angle and bending diameter.
Impact test
The measuring method of the steel toughness (impact toughness). The sample processed into a specified shape (different at the beginning of the gap on the specimen), hammer swing will sample thrust on the test machine, called the impact energy, the symbol for the Akv, units of joules or J.
In addition, there is hardness test, upsetting tests.