Q & A on practical knowledge of the hottest machin

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Q & A on practical mechanical knowledge 4

3: how many types of projection methods are there

answer: it can be divided into central projection method and parallel projection method, and parallel projection method can be divided into orthographic projection and oblique projection

4: what is a section view

answer: a group of parallel rays pass through the

figure obtained by the object on the projection plane

5 to remove rust and other sundries in the oil (water) pipe: what are the three basic views of the object projection

answer: front view, top view and left view

6: what is the projection law of three views

answer: the main view and top view are aligned; The height of the main and left views is flush; The top view

and the left view have the same width

7: what are the physical properties of metals

answer: including density, melting point, thermal expansion, conductivity and thermal conductivity

8: what is the melting point

answer: it refers to the temperature when the metal changes from solid state to liquid state

9: what is the chemical properties of metals

answer: it refers to the ability of metal materials to resist the corrosion of their surrounding chemical media at room or high temperature

10: what are the chemical properties

answer: including oxidation resistance and corrosion resistance

11: what is antioxidation

answer: the ability to resist oxidation at room temperature or high temperature

12: what is corrosion resistance

answer: the ability to resist the corrosion of water vapor and other substances at high temperature

13: what is mechanical property

answer: it refers to the ability of metal materials to resist external forces

14: what are the mechanical properties

answer: including strength, hardness, plasticity, toughness, fatigue strength, etc

15: what is deformation

answer: it refers to the

changes in the shape and size of metal materials under the action of external forces

16: what are the deformations of metal materials

answer: it can be divided into stretching, compression, bending, twisting and shearing

17: what is the elastic limit

answer: it refers to the maximum force that the material can bear in the elastic stage

18: what is yield strength

answer: it refers to the maximum stress that the material can bear when yielding occurs

19: what is tensile strength

answer: it refers to the maximum stress that the material can bear before breaking

20: what is plasticity

answer: it refers to the property that the material is easy to deform without fracture

21: what is the hardness of materials

answer: it refers to the ability of the material to resist other objects pressing into its surface

22: what are the expression methods of hardness

answer: Brinell hardness, Rockwell hardness and Vickers hardness

23: what is the process performance of metal materials

answer: it refers to whether the properties of metal materials are easy to process and shape

24: what are the technological properties of metals

answer: including castability, weldability, forging, machinability and heat treatment

25: what is alloy steel

answer: on the basis of carbon steel, in order to improve some mechanical properties of steel, it is necessary to add some alloy elements

26: what kinds of alloy steels can be divided into

answer: it can be divided into alloy structural steel, alloy tool steel and special purpose steel

27: what is cast iron

answer: iron carbon alloy with carbon content greater than 2.11% is called cast iron

28: what are the types of cast iron

answer: white cast iron, grey cast iron, nodular cast iron, alloy cast iron,

malleable cast iron

29: what are the simple identification methods for iron and steel

answer: Spark identification, fracture identification and color mark identification

30: what are the microstructure of the alloy

answer: solid solution, metal compound, mechanical mixture

31: what is the critical point

answer: the temperature at which the metal structure changes

32: what is quenching

answer: heat the steel to an appropriate temperature above the critical temperature, and quickly cool it after heat preservation to obtain martensitic structure

33: what is annealing

answer; Heat the steel to a certain temperature, hold it for a certain time, and then slowly

cool it to room temperature

34: what is hardenability

answer: the ability of steel to obtain a certain temperature quenching layer after quenching under certain conditions

35: what is tempering

answer: it is a method to heat the steel to a certain temperature below AC1 for a certain period of time, and then cool it to room temperature after the completion of

structure transformation

36: what is conditioning

answer: it is a heat treatment method combining quenching and high temperature tempering

37: what is the purpose of carburizing

answer: it is to make the active carbon atoms penetrate into the steel surface to improve the carbon content on the steel surface

38: what is thermal rigidity

answer: it refers to the ability of steel to maintain hardness at high temperature

39: what are the types of aluminum alloys

answer: it can be divided into deformed aluminum alloy and cast aluminum alloy

40: what are the types of copper alloys

answer: it can be divided into bronze, red copper and brass

41: what are the three kinds of tail flowers in spark identification method

answer: straight tail flower, spear tip tail flower, fox tail flower

42: what are the functions of welding rods

answer: it can conduct current and provide filler metal to the molten pool

43: what are the forces on the droplet

answer: there are gravity, surface tension, electromagnetic compression force, spot pressure, ISO

sub current force, arc gas blowing force

44: what are the defects that are easy to occur when gas welding cast iron

answer: mainly white spots, cracks, pores, refractory oxides, etc

45: what is weldability

answer: it refers to the adaptability of metal materials to welding processing, mainly refers to the difficulty of obtaining high-quality welded joints under certain welding process conditions

46: what are the main causes of stress and deformation during welding

answer: uneven heating and cooling

47: what is primary crystallization

answer: the process that the metal in the welding pool changes from liquid state to solid state

48: what are the common types of steels with special properties

answer: stainless steel, heat-resistant steel and corrosion-resistant steel

49: what are the types of titanium alloys

answer: type A, type B, and type A + B

50: how many types of riveting

answer: it mainly includes lap joint, corner joint and butt joint

51: what are the operation processes of hot riveting

answer: there are fastening and trimming nail holes of riveted parts, rivet heating, nailing and piercing

nails, top nails, riveting

52: what is screw connection

answer:; It is a detachable fixed connection composed of threaded parts

53: what are the common forms of threaded connection

answer: there are bolt connection, stud connection and screw connection

54: how many washers are there? What is its function

answer: it can be divided into general gasket, anti loosening gasket and special purpose gasket. The function is to increase the support surface, cover the large holes, and prevent damage to the surface of

parts and leveling

55: what are the washers to prevent loosening

answer: there are spring washers, round nut retaining washers, single lug retaining washers, and double

lug retaining washers

56: what are the important characteristics of tangent plane

answer: each point on the same prime line has the same tangent plane

57: what is developable surface

answer: if the three-dimensional surface can be flattened on a plane without tearing or folding, this kind of surface is called developable surface

58: what is an undevelopable surface

answer: if the three-dimensional surface cannot be naturally flattened on a plane, it is called non

developable surface

59: what are the characteristics of the deployment method

answer: first, divide the part surface into many small flat surfaces according to the three-dimensional surface properties, that is, use these small planes to approach the three-dimensional surface

60: what is the principle of parallel line expansion method

answer: the three-dimensional surface is regarded as composed of numerous parallel prime lines, and the small area surrounded by the connected two prime lines and their end lines is taken as the plane. As long as the real size of each small plane is drawn in sequence on the plane, the unfolded graph can be obtained

61: what is the principle of radiation expansion

answer: it is to divide the cone surface into several triangles with common tops by radiation, and draw them on the same plane

in the form of emission line after finding out their actual size

62: what are the steps of triangle expansion

answer: draw the necessary view of the component, divide the object surface with triangles, calculate the real length of each side of the

triangle, and draw the exhibition diagram in the order of triangles

63: what is the neutral layer

answer: when the sheet is bent, the outer material is stretched and the inner material is compressed. There is a fiber layer with constant length between elongation and shortening, which is called the medium layer

64: why should the plate thickness treatment be carried out

answer: when the plate thickness is greater than 1.5mm and the part size is required to be accurate, the plate

thickness treatment must be carried out. Otherwise, the size of parts will be inaccurate, the quality will be poor, and even waste products will be caused

65: what is the principle of plate thickness treatment

answer: the expansion length shall be subject to the size of the neutral layer of the component and shall be calculated; The curve height in the unfolded drawing is subject to the height of the component contact

pe water supply pipe 66: what are the main contents of plate thickness treatment

answer: determine the neutral layer of bending parts and eliminate the interference of plate thickness

67: what is blanking? What are the methods

answer: blanking is the process of separating parts or blanks from raw materials. The methods include cutting and gas cutting

68: what are the characteristics of shearing

answer: it has high productivity, smooth section, and can cut plates and various profiles

69: what is the essence of shearing

answer: the upper and lower cutting edges exert shear force on the material to cause shear deformation

and finally fracture and separation

70: what are the main measures to improve the quality of shear plane

answer: increase the strength of the cutting edge, take a reasonable cutting edge clearance and press the material on the lower cutting edge

71: what is the effect of the cutting rake angle on the cutting

answer: the size of the front angle not only affects the shear force and shear quality, but also directly affects the shear strength

72: does the shear back angle have and function

answer: the function is to reduce the friction between the material and the cutting edge. Usually, the back angle is taken as 1.5~3

73: what is the effect of shearing on the material properties

answer: it can cause material deformation and cold work hardening at the edge of the material

74: what are the characteristics of gas cutting

answer: the equipment is simple, with low cost and high production efficiency. It can cut at various positions in the space

75: what are the stages of oxygen acetylene cutting process

answer: it consists of three stages: metal preheating, combustion and oxide blowing

76: what conditions must be met for metal gas cutting

answer: (1) the ignition point of metal must be lower than its melting point. (2) The melting point

of the oxide generated by combustion should be lower than the melting point of the metal itself (3) the combustion of the metal should release a large amount of heat and the thermal conductivity of the metal itself should be low

77: why can't cast iron be gas cut

answer: because its ignition point is higher than the melting point, SiO2 with high melting point is generated, and the adhesion of oxide to other 2D nano materials is also widely valued

large degree, poor fluidity, high-speed air flow

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