Test method for strain aging sensitivity of steel (Charpy impact method) GB 4160-84

other standards 282 1064 Sophia

Introduction Xiebisheng test is a common tool used in among metallographers. It is a specially studied impact test which is capable of telling the user stress-strain sensitiveness of particular materials. In this test, a sample of material is evaluated for its property of sensitizing to strain an......

Introduction

Xiebisheng test is a common tool used in among metallographers. It is a specially studied impact test which is capable of telling the user stress-strain sensitiveness of particular materials. In this test, a sample of material is evaluated for its property of sensitizing to strain and stress. Basically, it measures the ability of material to demonstrate the change in mechanical behaviour when subjected to a specific level of strain, immediately followed by an amount of stress.

This test is mainly used to determine the stress-strain sensitivity of a material like ferrite-pearlite steel. Ferrite-pearlite steel is usually an iron-carbon alloy, which is essentially composed of ferrite and pearlite. This alloy is mainly used in engineering parts which often require the material to be ductile and having high dimensional stability, such as gears, shafts and engines.

The Xiebisheng method, sometimes referred as Ship-Impact test (SIT), was standardized by GB 4160-84, which divides the sampling into six A-E grades and prescribes the application of the method for each grade. Grade A prescribes the lowest amount of strain, while grade E prescribes the highest.

Contracting Principle

The Xiebisheng method generally applies to all kinds of ferrite-pearlite steel. The test basically consists of four main steps:

• Sampling: The first step is to select a sample for the test which should conform to the standardized sampling procedure.

• Pre-treatment: After taking the sample, the material should be prepared for evaluation. This includes pre-heating the sample, further processing through natural cooling, quenching and tempering.

• Test: This step involves subjecting a sample to stresses and strain. First, the sample should be subjected to stress at rated levels according to the grade it belongs. Then, in order to evaluate its sensitivity to strain, the sample is required to be subjected to strain at a level determined by the grade.

• Interpretation: In the last step, the behaviour of the sample is interpreted in terms of its sensitivity to the stress and strain applied.

Test Procedure

The Xiebisheng test comprises of the following stages:

1. Sampling: Before carrying out the test, a sample should be taken from the material in question using the prescribed sampling methods. The sample should conform to the standards laid out in GB 4160-84.

2. Pre-treatment: After the sample is taken, it should be heated to make it suitable for the test. The sample should be then quenched and tempered so as to make it in the proper conditions for the final test.

3. Marking: The sample should then be marked according to the standards defined in GB 4160-84. This step should be done carefully in order to avoid any confusion during the test.

4. Stress and strain application: After the sample is prepared, it should be stressed and strained according to the grade allocated. To achieve this, a stressor should be attached to the end of the sample and the other end should be clamped or held firmly. Strain should be applied slowly to reach the desired grade.

5. Interpretation: After the required strain and stress have been applied to the sample, its behaviour should be evaluated. This includes examining the sample for any deflection or damage caused due to the test.

Conclusion

The Xiebisheng Test is a well established stress-strain sensitivity test which is used to study the behaviour of ferrite-pearlite steels. The test consists of four steps: sampling, pre-treatment, stress and strain application, and interpretation. The method has been standardized by GB 4160-84 which prescribes the procedure to follow while carrying out the test. Therefore, this test is a reliable method and it provides accurate results when used properly.

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13/06/2023