Precipitation hardening stainless steels are chromium and nickel containing steels that provide an optimum combination of the properties of martensitic and austenitic grades. Like martensitic grades, they are known for their ability to gain high strength through heat treatment and they also have the corrosion resistance of austenitic stainless steels.
The high tensile strengths of precipitation hardening stainless steels come after a heat treatment process that leads to precipitation hardening of a martensitic or austenitic matrix. Hardening is achieved through the addition of one or more of the elements Copper, Aluminium, Titanium, Niobium, and Molybdenum.
The most well known precipitation hardening steel is 17-4Ph. The name comes from the additions 17% Chromium and 4% Nickel. It also contains 4% Copper and 0.3% Niobium. 17-4Ph is also known as stainless steels grade 630.
There are three main types of Ph stainless steel, namely:
1. Low Carbon Martensitic
2. Semi-Austenitic
3. Austenitic
You will be thrilled by how much you did not know about the most commonly used types of stainless steel. The following are Five things that you probably did not know about type 17-4Ph stainless steel:
1) Use of Type 17-4Ph Stainless Steel in Marine Vessels: The fact that 17-4ph has high mechanical strength and has super resistance to corrosion enables it to survive exposure to salty sea water.
Most of the parts of that ship that you went on that annual cruise are made from type 17-4Ph stainless steel. Most of the process piping, seawater piping, and heat exchangers are made of the alloy.
2) Use of Type 17-4Ph Stainless Steel in Nuclear Industries: Did you know that the alloy has been used in the nuclear power generation industry? Well, what usually happens during nuclear power generation is there is the use of fuel during the process. The used fuel should be given some time to cool and be stored in a dry cask.
The dry cask is usually fabricated using type 17-4Ph stainless steel. The design of the dry cask using type 17-4Ph stainless steel ensures that the radioactive spent fuel is in a safe storage design that is 100% leak proof.
3) Use of Type 17-4Ph Stainless Steel in Turbine Blade Design: In case you are familiar with the design of a turbine, then you are familiar with a combustor. If not, a combustor produces gas at a high pressure and temperature. It is the turbine blades that extract the energy that you need from these gasses.
In the past, one of the common causes of failure in turbine blades was a stress material failure and fatigue.Current turbine blade design makes use of super-alloys like type 17-4Ph stainless steel. The fact that the alloy has a high resistance and is able to keep its strength under adverse conditions like high temperatures makes it an ideal choice in turbine blade design.
So the next time you see a gas or windmill turbine at work, try and remember that it works because of the use of type 17-4Ph stainless steel in its construction. Even Most plane engine manufacturers like Pratt and Whitney or Rolls Royce make use of the alloy when designing the turbine blades for their massive engine.
4) Use of Type 17-4Ph Stainless Steel in Food Processing Equipment: The type 17-4Ph stainless steel is used in equipment for the processing and manufacture of foods and beverages. The fact that the alloy has a good surface condition and great finish makes it an ideal choice. The alloy’s smooth surface and high chromium content make it less prone to corrosion and makes it easy to clean as hygiene is an integral element of food and beverage manufacture.
5) Use of Type 17-4Ph Stainless Steel in the Oil and Gas Industry: There are two main reasons why the alloy is used, Firstly Oil is usually obtained at great depths, below sea level. Such depths are associated with high pressure. The high strength of type 17-4Ph stainless steel makes it a great construction material for piping at such depths. Secondly, Type 17-4Ph alloy is resistant to corrosion both on and offshore. Its resistance to corrosive media like hydrogen sulfide gas, carbon dioxide and low pH levels in oil prospecting conditions makes it the material of choice for oil rigs and pipes.
Conclusion: It is quite evident that type 17-4Ph stainless steel is the most used type of Ph stainless steel. It has an ideal combination of corrosion resistance, good mechanical properties at high temperatures and high yield strength. This combination makes it a suitable alloy for many applications. Its superior properties and cost effectiveness makes it the best, most used type of stainless steel.
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