Abstract
This article introduces the detection of eddy current of cold-drawn thin-wall tube material made of aluminum and aluminum alloy according to the national standard GB 5126-85. This method of eddy current testing is a reliable, high-efficiency nondestructive testing technology, which is widely used in industrial production. This article mainly introduces the characteristics and detection methods of eddy current testing of cold-drawn thin-wall tube material made of aluminum and aluminum alloy: the principle of eddy current testing of cold-drawn thin-wall tube material; the characteristics of eddy current testing of cold-drawn thin-wall tube material made of aluminum and aluminum alloy; various standards for eddy current testing of cold-drawn thin-wall tube material made of aluminum and aluminum alloy; technical requirements for eddy current testing of cold-drawn thin-wall tube material made of aluminum and aluminum alloy; the execution process and environment of eddy current testing. In the end, this paper emphatically indians the advantages and disadvantages of eddy current testing for cold-drawn thin-wall tube material made of aluminum and aluminum alloy.
Key words: Cold-drawn thin-wall tube, aluminum and aluminum alloy, eddy current testing, GB 5126-85
1 Introduction
Cold-drawn thin-wall tube material of aluminum and aluminum alloy is a general term for aluminum and aluminum alloy products with a wall thickness of not more than 3mm and an outer diameter of 10mm-60mm. This product should have some necessary characteristics in industrial production and manufacturing, including mechanical moisture resistance, heat conduction, conductivity, surface gloss, complete specifications and so on. That is why testing such a product is particularly important. Eddy current testing is one of the most widely used methods in the nondestructive testing of aluminum and aluminum alloy materials, and it is helpful to the customized purchase of aluminum and aluminum alloy materials.
2 Eddy current testing principle
Eddy current testing is a nondestructive testing method of electromagnetic waves, which is mainly used to detect the surface and internal defect defects on non-magnetic conductive materials. The eddy current testing device consists of an exciter coil and a detector coil. The principle of eddy current testing is to input alternating current into the exciter coil to generate an alternating magnetic field, which generates eddy current in the sample. The eddy current generates the magnetic field resistance force, which will affect the coil current of the detector. The changes of the detector coil current will be collected, processed, amplified and displayed on the oscilloscope. The defect is determined by comparing the results with the reference value.
3 Characteristics of eddy current testing of cold-drawn thin-wall tube material made of aluminum and aluminum alloy
(1) Eddy current testing of cold-drawn thin-wall tube material of aluminum and aluminum alloy can easily detect the surface and near-surface defects.
(2) Eddy current testing of cold-drawn thin-wall tube material of aluminum and aluminum alloy can directly indicate whether the material is qualified or not, so it is easy to make a judgment.
(3) The sensitivity of eddy current testing of cold-drawn thin-wall tube material of aluminum and aluminum alloy is better and the test range is wide.
(4) The comparison line (VL) of eddy current testing of cold-drawn thin-wall tube material of aluminum and aluminum alloy is clear, so test results can be more easily compared.
(5) Eddy current signal of cold-drawn thin-wall tube material of aluminum and aluminum alloy has good repeatability.
4 Eddy current testing standards for cold-drawn thin-wall tube material made of aluminum and aluminum alloy
The eddy current detection standards for cold-drawn thin-wall tube material of aluminum and aluminum alloy mainly include national standards, industry standards and military standards. The national standards are mainly GB5126-85 Aluminum and aluminum alloy cold drawn thin-walled tube eddy current testing method. GB5126-85 is mainly applicable to the surface and near-surface defects of round and square tubes with a thickness not greater than 3mm and an outer diameter not greater than 60mm. This method is often used as the standard method in the aluminum and aluminum alloy detection industry.
5 Technical requirements for eddy current testing of cold-drawn thin-wall tube material made of aluminum and aluminum alloy
Before the eddy current testing of cold-drawn thin-wall tube material of aluminum and aluminum alloy is carried out, the operator should check whether the sample size and coil are consistent, and the oil film on the sample surface should also be removed. After that, the eddy current testing of the sample can be carried out.
The testing environment should be controlled at 0~30℃, the relative humidity should not exceed 80%, and the sample should be cleaned. During the testing, ensure that the coil and sample are in good contact, and pay attention to the verticality and stability of the coil and sample. The testing results should be sent to the quality control department for archiving after testing and indicate the qualified or not qualified evaluation.
6 Execution process of eddy current testing of cold-drawn thin-wall tube material made of aluminum and aluminum alloy
(1) DATA preparation: determine the testing program and set the parameters, such as thresholding and comparison total scanning.
(2) Preparation before testing: check the equipment and sample shape and size conformity and measure the thickness of the sample.
(3) Taking samples: pay attention to the sample selection and inspection number.
(4) Executing Inspection: Scan the sample along the axial direction, pay attention to the speed, and understand the operation conditions of the instrument during the testing process.
(5) Evaluation of results: Compare the testing data with the national standards, industry standards and military standards, draw the comparison line, compare the current line with the comparison line, and make an evaluation of the results.
7 Advantages and disadvantages of eddy current testing for cold-drawn thin-wall tube material made of aluminum and aluminum alloy
Advantages: It can detect defects such as surface and near-surface defects of non-magnetic metal materials. It can detect near-surface defects more accurately, and has better sensitivity, good repeatability and reliability.
Disadvantages: In magnetic materials, eddy current testing has the disadvantage that it cannot detect defects. There are also some interferences in the testing process, such as temperature, humidity, etc.
