GB/T 25151.2-2010Fabrication and inspection method for high pressure urea equipment - Part 2: Selective corrosion examination and metallography examination for ultra low-carbon chromated nickel molybdenum austenitic stainless steel of urea grade (English PDF)

Foreword

GB/T 25151 "high pressure urea equipment manufacturing test method" is divided into six parts.

--- Part 1. Stainless steel with pole automatic surfacing ultrasonic testing;

--- Part 2. Urea grade ultra-low carbon chromium-nickel-molybdenum austenitic stainless steel selective corrosion inspection and metallographic examination;

--- Part 3. Urea grade ultra-low carbon chromium-nickel-molybdenum austenitic stainless steel to intergranular corrosion tendency test;

--- Part 4. urea grade ultra-low carbon chromium-nickel-molybdenum austenitic stainless steel to intergranular corrosion tendency test specimens prepared to take;

--- Part 5. High-voltage devices urea ammonia leak test methods;

--- Part 6. High-voltage devices urea helium leak test methods. This section GB/T 25151 Part 2: Appendix A of this section is an informative annex.

1 Scope

This section GB/T 25151 specifies the urea grade ultra-low carbon chromium-nickel-molybdenum austenitic stainless steel microstructure and selective etching depth inspection Sample selection, production, inspection items and methods.

This section applies to inter-urea grade ultra-low carbon chromium-nickel-molybdenum austenitic stainless steel grain inspection selective etching after the corrosion test and metallographic examination.

2 Sample selection and production

Select a sample of 2.1 Binocular stereoscopic microscope to check the sample surface for selective etching sample checks, should be 10 to 20 times, and to identify the most serious rot Pitting, and to locate this point intercept cross-section (see Figure 1), if the sample surface is difficult to determine the most severe corrosion at the site point, reference should surface around Corrosion determined. When as yet found, in the direction shown in Figure 1 press intercept any parallel sections (a), b), c), d), e)) or any interception A radial section (f), g), h)).

a) a sample plate b) SMAW welding sample c) SMAW welding and strip cladding specimens

d) automatic strip cladding specimens e) welded joint specimens Corrosion specimen cross-sectional position between different crystal Figure 1