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SOHIC Test

SOHIC开裂检测 Test Item

Stress-Oriented Hydrogen Induced Cracking, SOHIC

Purpose

Examine the resistance property of material to SOHIC

Test Range

Various metals

   Project Introduction

     The purpose of SOHIC test is to evaluate cracking sensitivity of carbon steel under the solution containing H2S. SOHIC test according to NACE TM 0103 is a more strict corrosion evaluation than SSC test.

      Carbon steel plate used for pressure vessel welding when working in wet H2S environment may suffer various forms environmental cracking.

      These crackings include:

      (1) Sulfide stress corrosion cracking of high hardness weld seam and heat affected zone (SSC);

      (2) Hydrogen-induced cracking of base metal (HIC);

     (3) Stress-oriented hydrogen induced cracking (SOHIC).

   Test method and standard

Test Methods

Test Standards

DB Test

NACE TM0103-2003

NACE TM0177 Method A

NACE TM0103-2003

   Sample requirements

Sample Size

Beams (mm)

Spacers (mm)

Tolerance (mm)

Width

Thickness

Length

Diameter

Separation Distance

Distance to Sample

Standard DB Sample

38

13

≥305

13

51

25

±0.13

Pony-size DB Sample

25

≥4.6

≥146

6.4

38

19

±0。13

试样安装

   Choice of test method

1) Materials’ anisotropism of mechanical property and sensitivity to environment cracking are important factors。 Specific factors of samples like rolling direction, stress direction, welding direction and others that related to  matters of manufacturing equipment need to be considered。

2) Current generated by electric contact of different metals can influence cracking sensitivity. Electric coupling increase the severity of the absorption of hydrogen in steel, which can increase the cracking sensitivity of steel.

3) Test temperature can influence cracking sensitivity。 Most laboratory evaluation was conducted in acidic solution at room temperature, and the sensitive steels。 But in some cases, the alkaline hydrogen sulfide environment and/or moderately elevated temperature may increase or reduce the efficiency of hydrogen absorption, thus affecting cracking sensitivity of steel, beyond the expectation of standard lab tests。

4) Different test methods can not provide material sensitivity in the same order。

5) Local heterogeneity materials (such as local slag and impurities segregation, as well as the number and morphology of nonmetallic inclusions) can affect the test results.

6) Because of the longer immersion time or more sample number may cause material failure under lower stress threshold value than the performance, obviously need to consider the cracking sensitivity threshold value for a particular test cycle。

7) Most environment promoting the cracking phenomena can be expressed by statistics and/or different variables. Test may be repeated to get a representative number, so that it can characterize the anti-cracking property of the test environment.

8) Some samples (such as subsurface or other characteristics and the welding area, etc.) are more suitable for measuring local cracking resistance than others. In addition, corresponding stress to failure time may need to be obtained, and in other cases, the experimental measurement of internal cracking is what we expect more, and that is more useful.

9) Usually, the test of full penetration sample is more demanding than the exposure test one side, can more directly to simulate the exposed surface morphology of pressure vessel, pipe and flow pipeline.

10) The immersed time of most laboratory tests are relatively short, can not make any given steels to produce maximum crack, but used to compare the different materials is enough.

   Laboratory

实验室环境

   Service process
Require
───Quick:Customer service reply consultation
 
Apply
───Standard:Fill in the application form, sign the agreement.
 
Testing
───Strictly:Strict compliance with the operating rules for the sample testing
 
Report
───Comply with the reporting procedures and ensure the accuracy of the data.
 
Archive
───Service:Archive customer's samples and contracts

RONDA TESTING——Science, Justice, Innovation, Efficient!

 

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