What are the principles for determining the dimensions of weld grooves in pressure vessels?

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The shape and size parameters of the groove that have a significant impact on the welded structure and weld quality are as follows: 1. Groove angle α – The magnitude of the groove angle has a great influence on the shape and cross-sectional area of the weld, and it directly affects the quality of the joint. When the groove angle is too small, the segregation resulting from welding will concentrate in the central part of the weld, thereby making hot cracks more likely to occur ； When the groove angle is too large, the amount of weld metal that needs to be added increases, and the thermal stress and thermal deformation associated with welding also increase; from an economic perspective, this is not cost-effective, nor is the welding efficiency high. II. Blunt edge height p: The blunt edge is provided primarily to prevent burn-through of the base material during welding. The principle for determining the height of the root edge is to avoid burning through the base material while ensuring full penetration. III. An appropriate gap b is left in the root area, with the aim of ensuring full penetration at the weld root. When the gap is too small, full penetration is often not achieved. When the gap is too large, more welding defects occur, and the tendency to develop welding cracks increases. IV. Root radius R (for U-shaped, J-shaped, etc.) The purpose of providing a radius at the root of U-shaped and J-shaped grooves is based on the welding metallurgy process; the value of this radius directly affects the width of the root area as well as the size of the entire groove cross-section. It is also related to various factors such as the feasibility of welding, the amount of weld metal deposited, and the welding heat input. V. Weld corner size K: The value of weld corner size K is a key parameter that ensures the strength and stiffness of fillet welds, lap welds, and T-joint welds. It also serves to reduce cross-sectional discontinuities and lower stress concentrations. However, an excessively large K value will increase the amount of deposited metal as well as generate excessive welding residual stresses and deformations.