Pumps and valves bolt used in machinery and equipment level are introduced

The use of bolt in the mechanical equipment is less than not, equipment composition, connection, fixed, and so on, bolt is a commonly used solid parts, bolt is also indispensable in the pumps and valves, bolts, there are many types of different types have different performance, so the water pump and valve structure connected with bolt performance level can be divided into 3. 6, 4. 6, 4. 8, 5. 6, 6. 8, 8. 8, 9. 8 and 10. 9 and 12. 9 and 10 levels, including 8. 8 and above bolt is made of low carbon alloy steel and medium carbon steel and the heat treatment ( Quenching and tempering) , known as high strength bolts, the rest is known as ordinary bolts. 4 a, such as: performance level. Level 6 of the bolt, the meaning is: 1, the bolt material nominal tensile strength of 400 mpa grade; 2, bolt material QuQiang ratio of 0. 6; 3, bolt material nominal yield strength of 400 & times; 0. 6 = 240 mpa level performance level 10. 9 high strength bolt, its material after heat treatment, can be achieved: 1, the bolt material nominal tensile strength of 1000 mpa grade; 2, bolt material QuQiang ratio of 0. 9. 3, bolt material nominal yield strength of 1000 & times; 0. 9 = 900 mpa grade bolts performance level is the meaning of international standards, the same level of performance of bolt, regardless of its material and the origin of the difference, its performance is the same, the design can only choose performance level. Strength grade eight. 8 and 10. 9 refers to the shearing stress of bolt rating of 8. 8 gpa and 10. 9GPa。 8. 8 nominal tensile strength of 800 n/was nominal yield strength of 640 n/was. General bolt is to use & quot; X。 Y' Said the intensity, X * 100 = the bolt tensile strength, X * 100 * ( Y / 10) Yield strength (= the bolt Because according to provisions of identity: yield strength tensile strength = Y / 10) Such as 4. Magnitude 8, the tensile strength of the bolt is: 400 mpa; Yield strength is: 400 * 8/10 = 320 mpa. Second, showed is ( Yield strength/tensile strength) , showed the higher, the reliability of the material, the better. Bolt performance rating label consists of two parts Numbers respectively represent the nominal tensile strength value of bolt material and QuQiang ratio. Three, tensile strength is uniform by the plastic deformation metal to make the transition to local concentration of plastic deformation threshold, and the bearing capacity of the metal under the condition of static stretching. Tensile strength is a characterization of uniform plastic deformation resistance, tensile samples before under tensile stress, the deformation is uniform, but beyond, metal began to appear necking phenomenon, namely concentrated deformation; For no ( Or small) Uneven plastic deformation of brittle material, it reflects the fracture resistance of materials. Symbol for Rm ( GB / T 228 - 1987 old gb regulation tensile strength symbol for & sigma; b） , the unit for the MPa. Four, yield strength is the metal material yield phenomenon occurs in the yield limit, is the stress of the micro plastic deformation resistance. For no obvious yield phenomena of metal materials, to produce 0. 2% residual deformation stress value as its yield limit, called conditions the yield limit or yield strength. Is greater than the yield strength of the external force, will make parts permanent failure, unable to recover. Such as low carbon steel yield limit is 207 mpa, when under external force is greater than the limit, the parts will produce a permanent deformation, less than this, parts will restore the original appearance.
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