1 iron carbon content of more than 2.11% yuan, the iron carbon alloy of iron, carbon and silicon.
A total of 2 yuan will be multi infiltration is steel, non-ferrous alloy workpiece with 3 or more than 3 kinds of main elements of the infiltration agent by vacuum heating, heat treatment process to obtain the workpiece surface alloy layer.
3. Yield point (sigma S) steel or specimens in tension, when the stress exceeds the elastic limit, even if the stress no longer increases, and steel or specimen continues to the obvious plastic deformation, said this phenomenon for yield and yield the minimum stress value is the yield point.
PS yield s point of force and fo samples of basal area, yield point sigma S =Ps/Fo (MPA) MPa said MPa is equal to N / mm2, (1MPa=106Pa, 1pA =1N/m2)
2, yield strength (sigma 0.2) some metal material yield point is not very obvious, the measurement is difficult, so in order to measure the material yield characteristics, the provisions of have a permanent plastic deformation is equal to a certain value (typically 0.2% of the original length) of stress, called conditional yield strength or referred to as yield strength sigma 0.2.
3, the tensile strength (b) material during the stretching process, the maximum reached from the beginning to break the stress value. It said the steel fracture resistance ability. The corresponding tensile strength and compressive strength, flexural strength etc..
Let Pb reach the maximum tension as the material is broken before, Fo for the sample section area, is the ultimate tensile strength b= Pb/Fo (MPa).
4, elongation (Delta s) material in fractured. The plastic percentage elongation length with the original length of the specimen called elongation and elongation.
5, the yield ratio (s/ b)
The yield point of steel (yield strength) and the ratio of tensile strength, yield ratio is called. Yield strength ratio is, the higher reliability of structural components, general carbon steel yield strength ratio for the 0.6-0.65 and low alloy structural steel as 0.65-0.75 alloy structural steel is 0.84-0.86.
4. To 120kg within the load and the vertex for 136 DEG diamond square cone pressing device is pressed into the surface material, with pits on the indentation of a material surface product divided by the load value, is the Vickers hardness value (HV)
5 pull test
According to the preparation of standard tensile specimen, installed in the clamping head of the tensile testing machine, the specimens are slowly applied uniaxial tensile stress, until the specimen is pulled so far test called tensile test.
The strength of metal materials under the action of external force, resistance to deformation and fracture ability called strength. The strength index includes: proportion limit, elastic limit, yield strength and tensile strength etc..
Proportional limit applied to the metal tension, the presence of metal focus and change the formation of the proportion of straight stage, and the stage of maximum load PP divided by the specimen of original cross-sectional area is proportional limit, with sigma P.
The elastic limit of metal deformation under the action of external force, the external force is removed, can fully restore the original shape, this deformation is called elastic deformation. The metal can maintain the maximum elastic deformation stress called the elastic limit, with a e said.
Tensile tensile strength of the sample, in the pull off before to withstand the maximum load divided by the original cross-sectional area from stress, referred to as tensile strength, sigma B said. When the material under external stress is greater than the tensile strength, the fracture will occur. The sigma B is higher, it can withstand greater stress without fracture.
Foreign standards of steel structure often according to the tensile strength to classification, such as SS400 and 400 of them that sigma B minimum value of 400MPa ultra high strength steel is steel sigma B is more than or equal to 1373 MPa.
The yield ratio of yield ratio is the ratio of the yield strength and tensile strength (o s/ o b). The yield ratio is high, the material strength is higher, the lower the yield strength ratio of plastic is better, the formability of the better. Such as deep drawing steel sheet yield ratio is less than or equal to 0.65.
Spring steel generally within the elastic limit the scope of service, load is not allowed to produce plastic deformation, thus requiring the spring steel after quenching and tempering is as high as possible in the elastic limit and the yield strength ratio (sigma S sigma B is more than or equal to 0.90) in addition to the fatigue life and the tensile strength and surface quality to have great relevance.