HIC test and SSC test
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This post was last edited by SSC Test HIC Test on 2019-4-16 09:32. Regarding the HIC tests and SSC tests used in corrosion testing within the metal industry today, I would like to explain first why these testing methods exist. Back in the early days, when China was extracting oil, metal pipes often cracked or broke due to the effects of petroleum gases or gas field solutions, resulting in significant losses. That’s why we began to study how other countries managed to avoid or prevent such issues. This method involves testing whether the metal will experience fracture or cracking in such a simulated environment before use. At the beginning of this experiment, we completely followed American standards – we did exactly as the Americans did. Many failures occurred right from the start. Now that technology has improved, cases of non-conformity are extremely rare. For the HIC test, the standards currently referenced are the national standard GB/T8650-2015 and NACE TM0284-2016. The acceptance criteria are hydrogen bubbling on one hand, and CLR, CTR, CSR on the other; in simpler terms, these are the ratio of crack length, ratio of crack width, and ratio of crack area. The national standard for SSC testing is GB/T4157-2017, the latest standard which introduces four-point bending loading as Method E. There is also NACE TM0177-2016. The main one here is the EC crack; for four-point bending loading, it is based on the yield strength and elastic modulus, while for constant load loading, it is based on the yield strength. In general, in domestic markets it is around 80% of the yield limit, while Japan requires 100% or even more. The hardness of the metal affects SSC stress corrosion; sampling issues need not be discussed. The UK is now adopting the BS8701-2016 standard, which is more comprehensive. This includes UT, sandblasting of garnets, data measurement of strain gauges during loading, deformation of the entire pipe, and X-ray analysis of the areas under maximum stress after 720 hours. If there are any issues, feel free to leave me a message so we can discuss them together. I also hope to work with everyone, and wish you all a happy life.
I just want to know why, when people from Fujian buy sulfur-resistant valves, they all choose WCB ones that don’t require any treatment. The manufacturers sell them to them in a self-righteous manner. Are anti-sulfidation pipes less likely to develop problems? Now, for sulfur resistance, the bolts and nuts need to be replaced, or even knocked off! Why do the tendering and procurement parties allow such phenomena to occur? They all just pass the buck after something goes wrong!
Let’s start with the positive aspects: the heat treatment processes for these materials are now very advanced, and their hardness generally meets the requirements of NACE treatment. Moreover, alternative materials specified in the NACE treatment requirements are generally chosen, such as austenitic stainless steel. The principle is the same for bolts and nuts. Therefore, many manufacturers believe that no special action is required for NACE treatment. Now, let’s talk about the negative side. It is also because many manufacturers view NACE treatment as too simple. Many detailed requirements were not taken into account. After all, this is also one of the drawbacks of fast-food culture these days – owners are always thinking about how to make quick money. So, basically, none of them hold up to close inspection.
Yes, but it actually needs to be handled as required. There is no such thing as overly advanced technology at the moment! It’s not that great actually; it’s just people from the same group cheating each other! There are also those who don’t know much about this, and they focus on hardness, pursue CE certification, and control the levels of S and P elements. But is a truly strict anti-sulfur operating condition really like that? Read more reports on hydrogen embrittlement in forums!
Many domestic low-alloy steels have no problems in terms of resistance to sulfur. Bidding relies heavily on connections; without them, the chances of winning are very low. Once the superficial aspects are taken care of, other factors are no longer considered.
The key is to consider the customer’s requirements; if it’s a critical area, strict standards will definitely be applied. For example, the implementation of more detailed standards such as NACE TM0177. For ordinary areas, in reality, one would just go with what’s available; it would be quite good if a standard specification could be requested, such as NACE0175 or 0103. I’ve seen cases where people didn’t specify anything other than requiring NACE treatment… There’s nothing else to do. First of all, the customer needs to understand what they actually want.
Are you professionals in this field? There should be a significant difference between the treated and untreated HIC SSC stainless steel. Do you have the HIC SSC test certificate? For stainless steel, this test is conducted – I’m not sure what the difference is! What conclusion can be drawn? The testing period is too long; even if the result is unsatisfactory, it still has to be dealt with!
Customers actually don’t understand much either; it can only be said that there are many customers like this these days, who know very little. I’ve encountered this too: you don’t say anything, and when you explain the standards to him, he just replies that everything should be handled in accordance with NACE requirements! Every time, it’s necessary to produce drawings for confirmation and clearly state the requirements on those drawings! !
That’s how reality is. However, for NACE0175 and 0103, the content consists of empirical summaries. Using the materials specified there is no problem (of course, those material requirements must be met), but in my humble opinion, if the customer does not require a formal test certificate, it is acceptable to choose experienced materials. I wonder how the original poster addressed customer NACE requirements.
The material selection is similar to yours; in both cases, the materials are chosen in accordance with NACE requirements. As for the requirements for procurement from our own factory, 1. The foundry must strictly control the chemical composition of S and P materials (test bars should be included with each batch of metal, as a backup). And issue a material report. 2. Then, upon returning to the factory, physical and chemical analyses are conducted to calculate the CE value. 3. Then determine the hardness requirements for the product! Relevant reports will be issued for all of the above! The above requirements are just for random checks! General requirements!
This one is the same. But from my perspective. Because castings from foundries often require patch welding. Therefore, if quality control is a concern, hardness testing of the welded areas must be required. I wonder if the foundries the original poster has come into contact with experience any repair work.