1. Yield point (σs) Steel or specimen in the tens […]
1. Yield point (σs)
Steel or specimen in the tensile, when the stress exceeds the elastic limit, even if the stress is no longer increased, while the steel or the sample still continue to undergo significant plastic deformation, called this phenomenon yield, and yield the phenomenon of the minimum stress value For the yield point.
Let Ps be the external force at the yield point s, Fo is the area of the specimen, then the yield point σs = Ps / Fo (MPa), MPa is called MPa equal to N (Newton) / mm2, (MPa = 106Pa, Pa: Pascal = N / m2)
2. Yield strength (σ0.2)
Some of the metal material yield point is very obvious, there are difficulties in the measurement, so in order to measure the yield properties of the material, the provisions of the permanent residual plastic deformation is equal to a certain value (usually 0.2% of the original length) when the stress, known as the conditions Yield strength or yield strength σ0.2.
3. Tensile strength (σb)
The maximum stress value achieved by the material during the stretching process from the beginning to the occurrence of fracture. It represents the ability of steel to resist fracture. And tensile strength corresponding to the compressive strength, bending strength and so on.
Let Pb be the maximum tensile force before the material is pulled off, Fo is the cross-sectional area of the specimen, then the tensile strength σb = Pb / Fo (MPa).
4. Elongation (δs)
After the material is broken, the length of the plastic elongation is the elongation or elongation as the percentage of the original sample length.
5. Yield ratio (σs / σb)
The ratio of the yield point (yield strength) to the tensile strength of the steel is called the yield ratio. The higher the strength ratio, the higher the reliability of structural parts, the general carbon steel yield ratio of 0.6-0.65, low alloy structural steel 0.65-0.75 alloy structural steel 0.84-0.86.
Hardness means the ability of the material to withstand the hard objects into its surface. It is one of the important performance indicators of metal materials. The higher the hardness, the better the wear resistance. Commonly used hardness indicators are Brinell hardness, Rockwell hardness and Vickers hardness.
⑴ Brinell hardness (HB)
With a certain load (usually 3000kg) to a certain size (diameter is generally 10mm) hardened steel ball into the material surface, to maintain a period of time, after loading, the load and its indentation area ratio, that is Brinell hardness ( HB) in kg / mm2 (N / mm2).
⑵ Rockwell Hardness (HR)
When HB> 450 or the sample is too small, can not use Brinell hardness test and switch to Rockwell hardness measurement. It is a support angle of 120 ° diamond cone or diameter of 1.59,3.18mm steel ball, under a certain load into the surface of the measured material, the depth of the indentation from the hardness of the material. According to the hardness of the test material, divided into three different scales to represent:
HRA: is the use of 60kg load and diamond cone press device obtained hardness, for high hardness materials (such as cemented carbide, etc.).
.HRB: is the use of 100kg load and 1.58mm diameter hardened steel ball, the hardness obtained for the lower hardness of the material (such as annealing steel, cast iron, etc.).
HRC: is the use of 150kg load and diamond cone press device obtained hardness, for high hardness materials (such as hardened steel, etc.).
Vickers hardness (HV)
The surface area of the indentation pits is divided by the load value, which is the Vickers hardness value (HV), by means of a diamond square cone presser with a load of less than 120 kg and a support angle of 136 °.
The first section of steel classification
1, black metal
Iron and iron are alloys. Such as steel, pig iron, iron alloy, cast iron and so on. Steel and pig iron are based on iron, carbon as the main element of the alloy, collectively referred to as iron-carbon alloy.
Pig iron is the iron ore into the blast furnace smelting from the product, mainly used for steel and manufacturing castings.
Cast iron into the melting furnace, that is, cast iron (liquid, carbon content greater than 2.11% iron and carbon alloy), the cast iron cast into castings, this cast iron is called cast iron.
Iron alloy is composed of iron and silicon, manganese, chromium, titanium and other elements of the alloy, ferroalloy is one of the raw materials of steel, steel in steel when the steel deoxidizer and alloying elements used.
Carbon content of less than 2.11% of the iron-carbon alloy called steel, the steel with iron into the steelmaking furnace according to a certain process smelting, that is, steel. Steel products are steel ingots, cast slabs and cast directly into various steel castings. Usually referred to the steel, generally refers to the rolling into a variety of steel steel.
2, non-ferrous metals
Also known as non-ferrous metals, refers to the metal and alloys other than black metal, such as copper, tin, lead, zinc, aluminum and brass, bronze, aluminum alloy and bearing alloys. In addition, the industry also uses chromium, nickel, manganese, molybdenum, cobalt, vanadium, tungsten, titanium, etc., these metals are mainly used as alloy additives to improve the performance of metal, including tungsten, titanium, molybdenum and other Of the cemented carbide. These non-ferrous metals are known as industrial metals, in addition to precious metals: platinum, gold, silver and other rare metals, including radioactive uranium, radium and so on.http://www.dreamhouseowner.com/