1. Metal mechanical properties include strength, plasticity, hard seat, toughness, fatigue strength, etc.

2. The hardness index can be divided into three types: Brinell hardness, Rockwell hardness and Vickers hardness.

3. The performance of metal materials to conduct heat is called thermal conductivity.

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

5. Heat-resistant steel refers to steel with certain thermal stability and thermal strength at high temperature.

6. Stainless steel is a stainless and acid-resistant flow scale that is resistant to atmospheric, acid, alkali, salt, etc. corrosion.

7. The performance of metal materials to conduct current is called conductivity, and its measurement index is resistivity.

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

9. Weld symbols are generally composed of basic symbols and guide lines. If necessary, auxiliary symbols, supplementary symbols and

weld size symbols can be added.

10. The symbol indicating that the surface of the weld is flush is one; the symbol indicating that there is a backing plate at the bottom of

the weld; the symbol indicating that the weld around the weldment is.

11. According to the 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 direct current, and vice versa is alternating current.

13. The stepped crack formed along the rolled layer of the steel plate in the welded component by welding is called lamellar tearing.

14. When other conditions remain unchanged, when the welding speed increases, the porosity tendency increases; when the welding current increases,

the porosity tendency increases; when the arc voltage increases, the porosity tendency increases.

15. Manual arc welding is suitable for welding various materials such as carbon steel, low alloy steel, heat resistant steel, low temperature steel and stainless steel.

16. Manual arc welding can be used for welding in various positions such as horizontal, vertical, horizontal and vertical, so it is widely used.

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

18. During manual arc welding, the welder's operating skills and experience directly affect the quality of the product.

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

20. Manual arc welding is mainly based on the performance of the base metal, the rigidity of the joint and the working conditions to select the electrode. For general carbon steel

and low alloy steel, the strength level of the electrode is mainly selected according to the principle of equal strength.

21. There are many factors that need to be considered in the selection of welding current for manual arc welding, but the main ones are electrode diameter, welding position, weld bead level.

22. The basic forms of grooves commonly used in manual arc welding are I-shaped, V-shaped, double V-shaped, double Y-shaped, double U-shaped groove with clanging edge.

23. Welding cracks are characterized by sharp notches and large aspect ratios.

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

25. The slag of alkaline electrode has strong desulfurization and dephosphorization ability.

26. Immediately after welding, the whole (or part) of the weldment is heated or insulated. The slow cooling process is called post-heating, which can effectively escape the hydrogen in the welded joint,

so it is an important measure to prevent delayed cracking.

27. During welding, the bubbles in the molten pool failed to escape during solidification, and the remaining voids formed are called pores.

28. The slag remaining in the weld after welding is called slag inclusion.

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

30. The length of the electrode depends on the diameter of the core, material, type of coating, etc.

31. Steel for welding core can be divided into three categories: carbon structural steel, alloy structural steel, stainless steel.

32. Electrodes can be divided into carbon steel electrodes, low alloy steel electrodes, stainless steel electrodes, surfacing electrodes, cast iron electrodes, nickel and nickel alloy electrodes, copper and

copper alloy electrodes, aluminum and aluminum alloy electrodes, special purpose electrodes.

33. The joints with relatively parallel end faces of the two weldments are called butt joints.

34. Butt joints without grooves are used for welding parts of thinner steel plates, and butt joints with grooves are used for thicker steel plates

Weldments requiring full penetration.

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

36. The function of the pressure reducing valve is to reduce the high pressure gas stored in the gas cylinder to the required stable working pressure.

37. When the mixing ratio β of oxygen and acetylene is 1.1-1.2, it is a neutral flame, when β>1.2, it is an oxidizing flame, and when β<1.1, it is a carbonizing flame.

38. Gas welding process parameters include wire diameter; flame properties and energy rate, tip tendency, welding speed.

39. Welding is a processing method in which the weldment achieves atomic bonding by heating, pressing or both, and with or without filler materials.

40. The basic symbol of the weld is the symbol representing the shape of the cross-section of the weld, a total of 13.

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

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

43. When welding non-ferrous metals, cast iron and stainless steel, it is usually necessary to use gas welding flux.

44. The safety of the acetylene bottle is realized by the fusible plug set on the bottle shoulder.

45. The ignition methods of the welding arc include the contact moment ignition method and the high frequency and high voltage arc ignition method.

46. The general structure of manual arc welding adopts acid electrode, and the important structure adopts alkaline electrode.

47. The slag characteristics of the welding electrode coating after melting, the electrode can be divided into acid electrode and basic electrode.

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

49. The metal cutting process includes three stages: preheating - burning heat - blowing slag.

50. In heat treatment production, the commonly used cooling methods are isothermal cooling and continuous cooling.

51. The necessary conditions for arc generation and maintenance are cathode electron emission and gas ionization.

52. The main source of sulfur in the weld is the base metal, welding wire, coating or flux, etc., so the key measure to reduce the sulfur content in the weld is to strictly

control the sulfur content in the welding raw materials.

53. The energy input from the welding energy to the unit length of the weld during fusion welding is called line energy.

54. The primary crystallization of the molten pool includes two processes: the generation of crystal nucleus and the growth of crystal nucleus.

55. In CO2 gas shielded welding, the nitrogen hole is caused by poor protection or impure CO2 gas.

56. The reverse wire methods of CO2 semi-automatic gas shielded welding include push wire type; wire drawing type; push-pull type;

57. The gas supply device of CO2 gas shielded welding consists of gas cylinder; dryer; preheater; pressure reducer; flowmeter and so on.

58. The welding equipment of CO2 gas shielded welding includes welding power source; welding torch; wire feeding system; gas supply device; control system, etc.

59. The methods of post-weld heat treatment include post-heating; high-temperature tempering; normalizing or normalizing and tempering.

60. The cracks generated when welding gray cast iron include thermal stress cracks; thermal cracks; two types, among which thermal stress cracks are more common.

61. For ductile iron thermal welding, cast 238 electrodes should be used.

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

63. For the structure of asymmetrical welds, the side with less welds should be welded first, and then the side with more welds should be welded, which can reduce the overall deformation.

64. In order to offset the welding deformation, artificially deform the weldment in the opposite direction to the welding deformation before welding. This method is called the reverse deformation method.

65. The heat dissipation method is not suitable for welding materials with high hardenability.

66. The flame straightening method uses the plastic deformation produced by the local heating of the flame to compress the longer metal after cooling, so as to achieve the purpose of correcting the deformation.

67. The key to flame heating correction is to grasp the deformation caused by the local heating of the flame, so as to determine the correct heating position, and at the same time, the temperature and the

number of repeated heating should be controlled.

68. The flame heating method is point-shaped heating; linear heating; triangular heating.

69. Triangular heating is often used to correct the bending deformation of components with large thickness and strong rigidity.

70. Preheating before welding can reduce the temperature difference and slow down the cooling rate, thereby reducing welding stress.

71. The acetylene bottle should be used upright. When the acetylene bottle is used directly, it must be left standing for 20 minutes before it can be used.

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

73. Before using the welding torch, check the injection and suction performance of the welding torch.

74. When welding stainless composite steel plates, three different solid electrodes should be used to weld the same weld.

75. If the torch is tempered, first turn off the acetylene and then turn off the oxygen.

76. When using carbon steel electrode to connect cast iron and low carbon steel joints, a 4-5mm isolation layer can be surfacing on the cast iron groove first, and then the assembly spot welding can be carried out after cooling.