Chapter VI Summary

Welding testing is one of welding professional disciplines which based on modern physics, chemistry, mechanics,electronics and materials,It can help students with the basic knowledge and skills of Welding testing which can also help them become qualified and specialized.Many advanced testing methods 、 equipments and instruments 、 management systems are involved in welding testing and become the important guarantee for modern welding industrial products.

1. The significance of welding testing Now welded products and welding technology have been widely applied in modern science and production with the development of industrial technology,especially in boilers manufacturing, pressure vessels,chemical machinery, marine equipment,shipbuilding, aviation,bridges built,nuclear engineering,lifting appliance,locomotive manufacturing industries,welding quality has played a vital effect on the quality of products.

1. The significance of welding testing

1. The significance of welding testing

1. The significance of welding testing Just for the operating features of welded structures,it may cause heavy losses if the product failures,so,in order to protect the quality of welded fabrications,we need to continue to adopt and develop a reasonable and advanced welding testing technology. （ 1 ） To ensure the manufacturing quality of welded structure ； （ 2 ） To improvement welding procedure ； （ 3 ） To reduce product cost ； （ 4 ） To promote the dissemination and application of welding technology.

2 、 Classification of welding testing The purpose of welding testing is to guarantee the product quality through the sampling and analysis,measurement,testing, real-time monitoring and other methods,and it takes effect throughout the production process.

2 、 Classification of welding testing Welding testing may be classified and named for destructive examination and nondestructive examination. Nondestructive examination is also named as non- destructive testing,it is a method which not damages the welding materials and the integrality of products. Destructive examination is used to test various mechanical properties 、 chemical composition 、 weldability,etc,through cutting off welded specimens from weldment or destroying the whole weldment.

2 、 Classification of welding testing

3 、 Appearance test Appearance test is used to check welding defects with naked eye or magnifying glass.We can examine the welded units that wheather they satisfy the product design requirements, whether the welded joints continue to have welding cracks 、 cells 、 lack of fusion 、 incomplete fusion 、 undercuts 、 excessive penetration 、 weld penetration and so on,whether the reinforcement and weld width fit the technical requirements,etc. There are many reasons causing these defects,such as the size of beveled edges and root face 、 the precision of assembly 、 the manipulation of electrode and the like.

[Welding cells ] [ Welding cracks ] [ Cinder inclusion ] welding cracks

[ Incomplete fusion ] [ lack of fusion ] [ Undercuts ]

4 、 Method of non-destructive testing Now let’s focuses on four kinds of non-destructive testing methods commonly used.

5 、 Mechanical performance test (1) Preparation of welding test panels a. The material of test panels should be the same as products; b. Shape and size:  Thickness ： the same as welding plates;  Width ： 250 ～ 300mm ；  Length ： based on intercepting enough specimen, the length of discard ： hand welding≥30mm; automatic welding ≥40mm.

c. test panels Using the same welding procedure as welding products during the construction process. d. The number of test panels In accordance with ‘procedures’ (2) Test content and method a. Tension test 1) Size and number of test panels Number:two;

Width≥25mm; Thickness ： When the plates ’ thickness≤ 30mm,use full- thickness ； When the plates ’ thickness≥ 30mm,use more pieces. 2) Technical requirements Tensile strength should be not less than one of the following provisions: The specified value of product drawings ； Minimum tensile strength of steel in standards ； The smaller tensile strength in different-strength steels joints 。

b. Bending test 1) Size and number of test panels :if δ<20mm, face bend one piece, back bend one piece ； if δ≥20mm ， side bend two pieces. 2) Technical requirements ： There are any longer than 3mm vertical cracks or flaws on the stretched surface by any

c. Impact test 1)The n umber of test panels Generally take three weld panels;when the design temperature ≤- 20 ℃,you must do three HAZ impact panels. The provisions of the bending test angle

2) Technical requirements ： The average impact energy at room temperature must be not less than 27J; The average impact energy at low- temperature can not be less than the average value of the following table. Single value cannot be less than 70% of specified value.

6 、 Basis of welding testing Welding production must follow requirements of the patterns,technical standards and testing documents. (1)Shop drawings Shop drawings are the most basic data used in production,manufacture should be in accordance with the provided patterns. (2) Technical standards Including those relational technical conditions. (3) Testing files Including process specification 、 inspection procedures 、 testing procedures,etc. (4) Purchase contract The product quality of welding which users require in the contract,can be used as the supplementary provisions of drawings and technical documents.

7 、 Process of welding testing (1)Welding pre-testing (2)Welding process test (3)Post-weld testing (4)The quality testing of installation and debugging (5) The product quality testing in service