1. What is the welding condition? What does it have?

Answer: The surrounding conditions during welding include: base metal material, plate thickness, groove shape, joint form, restraint state, ambient temperature and humidity, cleanliness, and the type and diameter of welding wire (or electrode), welding current, voltage, welding speed, welding sequence, deposition method, gun (or strip) method, etc. determined according to the above factors.

2. What is a welded joint? There are several basic forms?

Answer: joints connected by welding method. The welded joint consists of weld, fusion zone and heat affected zone. The basic forms of joints are: butt joint, corner joint, lap joint and T-shaped joint.

3. What is penetration?

Answer: In the cross section of the welded joint, the depth of the base metal melting.

4. What is the welding position? There are several forms?

Answer: When welding, the space position of the weldment joint. There are flat welding, vertical welding, horizontal welding and overhead welding and other forms.

5. What are downward vertical welding and upward vertical welding?

Answer: <1> vertical welding, arc welding from top to bottom-called vertical welding. Such as: cellulose welding rod downward vertical welding; CO2 downward vertical welding, etc.

<2> vertical welding, arc welding from bottom to top-called upward vertical welding.

6. What is a welded structure?

Answer: The steel structure connected by welding method is called welded structure.

7. Why is it necessary to open a groove to the weldment?

Answer: groove-according to the design or process requirements, the weldment to be welded parts processed into a certain geometric shape, the groove formed after assembly. In order to weld cross-section penetration and reduce the fusion ratio; commonly used groove forms are: I, V, Y, X, U, K, J type, etc.

8. Why is it necessary to preheat certain materials before welding?

Answer: In order to slow down the cooling rate of weldments after welding and prevent cold cracks.

9. Why do some welded components need heat treatment after welding?

A: In order to eliminate welding residual stress and improve the organization and performance of welded joints.

10. Why should welding procedures be formulated before welding?

Answer: To ensure the welding quality depends on five control links: human, machine, material, method and ring.

Human-operation skills and experience of welders

High performance and stability of machine-welding equipment

Materials-High quality of welding materials

Method-correct welding procedures and standardized operations

Ring-good welding working environment

According to the welding test and welding procedure qualification before welding, the welding procedure specification is "regulation" and is an important factor to ensure the welding quality.

11. Why is it necessary to process the surface of the base metal before welding?

Answer: If there are oil (paint), water, rust and other impurities on the groove and surface of the weldment, defects such as pores, inclusions, slag inclusions, cracks and the like will be produced when melted into the weld, bringing harm and hidden dangers to the welded joint.

12. What is the melting coefficient of welding wire?

Answer: The melting coefficient of the welding wire refers to the melting amount of the welding wire when the unit current passes through the unit time. (g/Ah)

The finer the welding wire, the greater the melting coefficient and the higher the efficiency.

13. What are the welding process parameters?

Answer: When welding, in order to ensure the quality of welding and the selected physical quantities (such as: welding current, arc voltage, welding speed, line energy, etc.).

14. What is the welding current?

Answer: When welding, the current flowing through the welding circuit is generally expressed in amperes (A).

15. What is arc voltage?

Answer: The voltage drop between the two ends of the arc (the two electrodes) is generally expressed in volts (V).

16. What is the welding speed?

Answer: The length of the weld completed per unit time is generally expressed in centimeters per minute (cm/min).

17. What is dry elongation?

Answer: When welding, the distance between the end of the welding wire and the end of the contact tip.

18. What is the welding line energy?

Answer: When welding, the energy input by the welding heat source to the unit length of the weld, also known as "heat input". Generally expressed in joules per centimeter (J/cm).

19. What is the fusion ratio of weld metal?

Answer: When welding, the proportion of the molten base metal in the weld metal.

20. What is the weld shape factor?

Answer: When welding, the ratio of weld width to weld thickness on the cross section of a single weld.

21. What is the left welding method?

Answer: When welding, the welding torch moves from the right end of the weldment joint to the left. The gas protection effect is good, and the weld is beautiful. CO2 and TIG welding shall use the left welding method; MIG welding aluminum must use the left welding method.

22. What is the right welding method?

Answer: When welding, the welding torch moves from the left end to the right end of the weldment joint.

23. Why is the welded joint the weak link in the welded structure?

Answer: Because the welding joint has the inhomogeneity of organization and performance, there are often some welding defects and high tensile residual stress. Therefore, the welding joint is the weak link in the welding structure.

24. Why is it said that high-quality welded joints can be obtained through the process?

Answer: To improve the quality of welded joints, we can start from the following ways: correctly selecting welding materials, adopting reasonable welding process methods, controlling fusion ratio, adjusting welding thermal cycle characteristics, using reasonable operation methods and groove design, supplemented by preheating, interlayer heat preservation, slow cooling, post-heating and other measures, or post-welding heat treatment methods, etc., to obtain high-quality welded joints.