1. The mechanical properties of metals include strength, plasticity, hard seat, toughness, fatigue strength, etc.

2. Hardness index can be divided into Brinell hardness, Rockwell hardness and Vickers hardness.

3. The ability of a metal material to conduct heat is called thermal conductivity.

4. The physical properties of metals include density, melting point, thermal expansion, thermal conductivity, conductivity, etc.

5. Heat resistant steel is a kind of steel with certain thermal stability and thermal strength at high temperature.

6. Stainless steel is a stainless and acid resistant fluid with the corrosion resistance to atmosphere, acid, alkali, salt, etc.

7. The property of conducting current of metal materials is called conductivity, and its measurement index is resistivity.

8. The temperature at which a metal changes from a solid state to a liquid state is called the melting point.

9. Weld symbols are generally composed of basic symbols and leader lines. If necessary, auxiliary symbols, supplementary symbols and weld size symbols can be added.

10. The symbol indicating that the weld surface is flush is one; Symbol picture indicating that there is a backing plate at the bottom of the weld; The symbol representing the weld around the weldment is o.

11. According to different heating and cooling methods, heat treatment can be divided into annealing, quenching, normalizing and tempering.

12. The current whose direction and magnitude do not change with time is DC, on the contrary, it is AC.

13. The ladder like cracks formed along the rolling layer of the steel plate in the welded components due to welding are called lamellar tearing.

14. With the increase of welding speed, the tendency of porosity increases under other conditions; When the welding current increases, the tendency of porosity increases; When the arc voltage increases, the pore tendency increases.

15. Manual arc welding is applicable to the welding of carbon steel, low alloy steel, heat resistant steel, low temperature steel, stainless steel and other materials.

16. Manual arc welding can be used in horizontal, vertical, horizontal, vertical and other positions, so it is widely used.

17. Compared with gas welding and submerged arc welding, manual arc welding has fine microstructure and good performance of small joint in heat affected zone.

18. During manual arc welding, the operation technology and experience of welders directly affect the quality of products.

19. Welding process parameters refer to the physical quantities selected to ensure the welding quality during welding.

20. The electrode for manual arc welding is mainly selected according to the performance of the base metal, the rigidity of the joint and the working conditions. The strength grade of the electrode for welding general carbon steel and low alloy steel is mainly selected according to the equal strength principle.

21. There are many factors to be considered when selecting welding current for manual arc welding, but the main factors are electrode diameter, welding position and weld bead level.

22. The empirical formula for calculating welding current of manual arc welding is i=10d2.

23. The basic forms of grooves commonly used in manual arc welding include I-shaped, V-shaped, double V-shaped, double Y-shaped and double U-shaped grooves.

24. The welding crack has the characteristics of sharp notch and large aspect ratio.

25. The purpose of preheating is to reduce the cooling rate and improve the stress condition.

26. The slag of alkaline electrode has strong desulfurization and dephosphorization capacity.

27. After welding, all (or part) of the weldment shall be heated or insulated immediately. The process measure of slow cooling is called post heating, which can effectively make the hydrogen in the welded joint escape, so it is an important measure to prevent delayed cracks.

28. During welding, bubbles in the solution pool cannot escape during solidification, and the remaining holes are called pores.

29. The residual slag in the weld after welding is called slag inclusion.

30. The coating layer pressed on the surface of the welding core is called coating.

31. The length of welding rod depends on the diameter of welding core, material, coating type, etc.

32. Steel used for welding core can be divided into carbon structural steel, alloy structural steel and stainless steel.

33. Welding rods can be divided into carbon steel welding rod, low alloy steel welding rod, stainless steel welding rod, surfacing welding rod, cast iron welding rod, nickel and nickel alloy welding rod, copper and copper alloy welding rod, aluminum and aluminum alloy welding rod and special purpose welding rod according to different purposes.

34. The joint where the end faces of two weldments are relatively parallel is called butt joint.

35. The butt joint without groove is used for the weldment of thinner steel plate, and the butt joint with groove is used for the weldment of thicker steel plate that needs full penetration.

36. Acetylene generator is a device that uses the interaction of voltage and water to produce acetylene.

37. The pressure reducing valve is used to reduce the high-pressure gas stored in the gas cylinder to the required stable working pressure.

38. Mixing ratio of oxygen and acetylene β It is neutral flame when it is 1.1~1.2, β> 1.2 is oxidation flame, β< 1.1 is carbonization flame.

39. Gas welding process parameters include welding wire diameter, flame property and energy rate, welding nozzle tendency and welding speed.

40. Welding is a processing method that enables the weldment to achieve atomic bonding by heating, pressurizing or using both, with or without filler materials.

41. There are 13 Basic weld symbols representing the weld section shape.

42. The included angle between the vertical of the weldment surface and the groove surface is called the groove surface angle.

43. The junction between the weld surface and the base metal is called the weld toe.

44. When welding non-ferrous metals, cast iron, stainless steel and other materials, gas welding flux must be used.

45. The safety of acetylene cylinder is realized by the fusible plug on the cylinder shoulder.

46. The ignition method of welding arc includes contact moment ignition method; High frequency and high voltage arc striking method.

47. The general structure of manual arc welding shall be acid electrode, and the important structure shall be alkaline electrode.

48. According to the slag dissolving characteristics of the electrode after melting, the electrode can be divided into acid electrode and alkaline electrode.

49. The safety of the oxygen cylinder is realized by the metal safety film in the cylinder valve.

50. The metal cutting process includes three stages: preheating, burning and slag blowing.

51. In heat treatment production, there are two common cooling methods: isothermal cooling and continuous cooling.

52. The necessary conditions for the generation and maintenance of arc are cathode electron emission and gas ionization.

53. The main sources of sulfur in welds are base metal, welding wire, coating or flux, so the key measure to reduce the sulfur content in welds is to strictly control the sulfur content in welding raw materials.

54. During fusion welding, the energy input from welding energy to the weld of unit length is called linear energy.

55. Primary crystallization of molten pool includes two processes: nucleation and nucleation growth.

56. In CO2 gas shielded welding, nitrogen pores are caused by poor protection or impure CO2 gas.

57. There are three reverse wire methods for CO2 semi-automatic gas shielded welding: push wire type, pull wire type and push-pull type. At present, push wire type welding gun is mostly used.

58. The gas supply device for CO2 gas shielded welding is composed of gas cylinders, dryers, preheaters, pressure reducers, flow meters, etc.

59. The welding equipment for CO2 gas shielded welding includes welding power supply, welding gun, wire feeding system, gas supply device, control system, etc.

60. Post welding heat treatment methods include post heating, high temperature tempering, normalizing or normalizing plus tempering, etc.

61. When welding gray cast iron, there are two kinds of cracks: thermal stress crack and thermal crack, of which thermal stress crack is more common.

62. Cast 238 welding rod shall be used for hot welding of nodular cast iron.

63. The stress and deformation of the weldment in the direction perpendicular to the weld is called transverse stress and deformation.

64. For the structure with asymmetric welds, the side with fewer welds shall be welded first, and then the side with more welds, so as to reduce the overall deformation.

65. In order to offset the welding deformation, the weldment shall be artificially deformed in the direction opposite to the welding deformation before welding. This method is called anti deformation method.

66. Heat dissipation method is not applicable to materials with high welding hardenability.

67. Flame correction method is to use the plastic deformation caused by local heating of flame to compress the longer metal after cooling, so as to achieve the purpose of deformation correction.

68. The key to flame heating correction is to master the deformation caused by local flame heating, so as to determine the correct heating position, and control the temperature and the number of repeated heating.

69. The flame heating methods include point heating, linear heating and triangle heating.

70. Triangle heating is often used to correct the bending deformation of members with large thickness and strong rigidity.

71. Preheating before welding can reduce the temperature difference and slow down the cooling speed, thus reducing the welding stress.

72. The acetylene cylinder shall be used vertically. When the acetylene cylinder is placed horizontally, it must stand for 20min before use.

73. The pressure reducer shall not be contaminated with grease during use.

74. Before using the welding torch, it is necessary to check the emission and absorption performance of the welding torch.

75. Three different Dacron electrodes shall be used to weld the same weld when welding stainless clad steel plate.

76. If the welding torch backfires, first turn off acetylene and then turn off oxygen.

77. According to the provisions of the national standard gb3323-82 "classification method for fair trade of steel weld radiography and negatives", the quality standard for radiographic testing of steel welds is divided into four levels, of which the defects in grade I welds are the least and the defects in grade IV welds are the most.

78. According to gb3323, cracks, incomplete fusion, incomplete penetration, strip slag inclusion, cracks and incomplete fusion are not allowed in class I welds, and incomplete penetration in double-sided welding or single-sided welding with backing plate is not allowed in class II welds.

79. When carbon steel electrode is used to connect cast iron and low carbon steel joint, 4~5mm isolation layer can be deposited on the cast iron groove first, and then assembly spot welding can be carried out after cooling.

Source: metal processing network