A. Brief overview of 304 and 316 stainless steel
Stainless steel, which is a class of steel, consists of five types and 304 and 316 stainless steel are two of them. Normally, in human eyes, 304 and 316 stainless steel appear the same and it is difficult to see the contrast by looking. The differences are usually noticed during the manufacturing process involving the two. Most industries use the two kinds of stainless steel to produce various products according to their favorable features.
B. Importance of understanding their differences
It is important to learn the differences between 304 and 316 stainless steel since each has the production sectors it is well suited for, due to their different features. For the efficiency of the end products made of stainless steel, it is important to ensure that the right type of stainless steel is used. In this post, we will discuss everything about the two families of stainless steel.
A. Chemical makeup of 304 stainless steel
Chromium and nickel content
304 stainless steel is usually considered the most flexible and the one that is commonly used. It is basically made up of iron which consists of 67 to 71.5%, 18% chromium, and 8% nickel which gives it the name 18/8. It also contains 0.08% of carbon, 2% of magnesium, 0.045% of phosphorus,0.03% of sulfur, and 1% of silicon. This type of steel is broken down into three types which include; 304, 304L, and 304H, which are usually different about the amount of carbon they possess. This family can also be referred to as 1.4301.
B. Chemical makeup of 316 stainless steel
Chromium, nickel, and molybdenum content
On the other hand, 316 stainless steel is made up of 16 to 18% of chromium, 11 to 14% 0f nickel, and 2% of molybdenum. It also consists of 0.08% of carbon, 0.75% of silicon, 0.045% of phosphorus, and 0.03% of sulfur. It comprises elements of 316L, the version with little carbon, 316H, and 316Ti.
III. Corrosion Resistance
A. Corrosion resistance in 304 stainless steel
Suitable environments and applications
304 stainless steel has very good resistance to corrosion in various kinds of environments after coming into contact with corrosives. It is also capable of resisting oxidation in irregular and continuous services up to 8700C and 9250C respectively due to its high resistance to heat. However, it is not advisable to use temperatures of 425 to 8600C consistently since it may result in corrosion. It has a melting point of between 1400 and 14500C and a density of 7.93 g/cm3.
B. Corrosion resistance in 316 stainless steel
Enhanced resistance due to molybdenum
316 stainless steel contains molybdenum which is a chemical added to it unlike 304. This additional chemical increases its level of corrosion resistance more than any other type of stainless steel. Its high resistance to chloride and corrosion makes it suitable for marine conditions.
Suitable environments and applications
However warm seawater cannot be resisted by 316 hence resulting in crevice corrosion. It also gets stress corrosion cracks when temperatures are raised more than 600C. 316 is usually resistant to heat when the temperature exceeds 8430C or less than 4540C. It has a melting point of 1378 to 13900 C and a density of 8.03g/cm3C. Grade 316H is usually preferred in cases where there is a need for high strength and temperatures of more than 5000C.
IV. Strength and Mechanical Properties
A. Comparison of tensile strength and yield strength
The two stainless steel families have almost the same tensile strength whereby 316 stainless steel has an ultimate tensile strength of between 620 and 795 MPa and a yield strength of 206Mpa. 304 stainless steel on the other hand has a tensile strength of between 515 MPa and 625 MPa while the yield strength lies at 205 MPa. In cases where the steel is subjected to stress that is more than 205 MPa, it results in it being disfigured forever with no possibility of reversal. Cold working is performed on 304 so as to harden it more and to make sure that there is no cracking or tearing.
B. Hardness and ductility
In terms of hardness, 304 stainless steel has a 40% elongation, a 201 Brinell hardness which is usually the maximum, and a 92 Rockwell hardness. 316 stainless steel has a maximum hardness of 95 Rockwell B and a maximum of 217 Brinell hardness. In terms of ductility, 304 stainless steel is more ductile than 316 stainless making 304 easier to machine. Rapid prototyping uses stainless steel due to the above features such as its resistance to corrosion, its tensile strength, and the fact that they don’t easily rust.
V. Cost and Availability
A. Price difference between 304 and 316 stainless steel
When it comes to their prices, 316 stainless steel is usually considered to be 40% more expensive than 304 stainless steel. This is so due to the fact that the production process of 316 is more costly than that of 304. In the production that involves 316, there is a requirement for more alloys such as nickel, to be added hence increasing the cost. The addition of nickel to 316 is important since it helps the material to be more versatile and efficient in the production process. Molybdenum is also added so as to boost its level of resistance to corrosion making 316 the most resistant stainless steel. Conversely, 304 does not have a lot of alloys which helps to make the production process cheaper.
A. Common uses for 304 stainless steel
The two types of stainless steel are used by a number of industries in their day-to-day production processes. First, we will discuss the applications of 304 stainless steel.
- In the food industry, 304 is the most commonly used due to its ability to resist corrosion and oxidation which is enabled by the high amount of nickel in it and chromium which helps to prevent rusting. Most appliances used in the food industry production processes, such as beer brewing and milk processing, are made out of 304. It is also used in the storage of end products.
- Also, it is used in the manufacturing of domestic tools. This is again due to its ability to resist the corrosion that may come from various items such as fruits, meat, and some vegetables. This helps to ensure that the appliances last longer. In the same sector, it is also used in the manufacturing of sinks, refrigerators, tables used for steaming, milk dispensers, and stoves. The pots and pans used for cooking are also made from 304 due to their high ability to withstand heat.
- 304 is used in the manufacture of chemical containers for storage as well as the ones used to transport the chemicals.
- It is used in industries to make fasteners such as screws, bolts, nuts as well as handles.
- Automotive industries as well as aerospace industries use 304 in the manufacture of fuel tanks and other components of the machines. Such industries use stainless steel due to its high resistance to corrosion and they often use CNC machining.
- Hospitals also make use of it in the manufacture of various surgical tools.
- This type of stainless steel is also used when presenting various foods such as cake stands due to its resistance to chemical reactions.
- 304H is usually used in the architectural sector because of its durability, strength, and the fact it does not need a lot of maintenance. It is used in petroleum refineries to make heat exchangers.
- 304 stainless steel is also used in the manufacture of a variety of tubes that have the possibility of coming into contact with various chemicals.
304 stainless steel has properties that make it achieve the above applications. They include;
- It is not magnetic and also withstands corrosion and oxidation which are caused by chemicals due to the presence of chromium as one of its elements.
- It is suitable for welding due to weldability. The preferred filler for 304 stainless steel is 316 stainless steel.
- It is capable of remaining strong even at exceptionally low temperatures.
- Its surface is smooth which makes it easy to keep it clean.
- It is also cheaper and more readily available compared to 316 stainless steel.
Generally, 304 stainless steel is usually easy to machine due to its excellent machinability. This feature can be increased through the following rules;
-Ensure sharp cutting of edges since edges that are not sharp lead to excess hardening work.
-You should also ensure that the cuts are deep enough but light to ensure easier work.
-It is advisable to use cooling aids and lubricants to ensure no heat is compressed on the cutting edges.
B. Common uses for 316 stainless steel
316 stainless steel is, on the other hand, used in various sectors which include the following.
- 316 is mainly recognized because of its high resistance to corrosion and chloride because of its element, molybdenum, which is responsible for boosting its resistance. This feature makes it most suitable to be used in the marine industry due to the presence of water bodies that may contain chlorine and other chemicals. Refineries, boats, and buildings near the seas are all built using this type of stainless steel.
- 316L, which is an element of 316, is used in the production of equipment used in pharmacies and photography due to its ability to resist reactions that may be caused by corrosive chemicals.
- It is also used in the medical industry because of its ability to withstand chemicals in the manufacture of equipment to be used in the medical sector.
- It is used in the manufacture of tools used to extract oil and gas. This is because of its durability and ability to resist corrosion. They are in the making of apparatus that is used in the extraction process and the pipelines through which the oil is transported.
- It is used in the manufacture of parts for a jet engine.
- It is also used in the production of surgical tools too due to its unresponsive nature to chemicals.
- It is also used in the production and processing of food in environments that involve sodium chloride and water.
- It is used in the production of pressure vessels.
This type of stainless steel also has a number of advantages that make it suitable for the uses above. Some of these advantages include the following.
- It is very well resistant to corrosion which is generally considered a common occurrence. When iron comes into contact with oxygen present in water, rust is formed. However, stainless steel contains chromium which helps to create a layer that averts corrosion. In 316, there is also molybdenum which adds to the resistance.
- It does not weaken after exposure to high temperatures. It is more heat resistant than 304 stainless steel.
- It is easy to machine during the production process.
- It is suitable for the welding process since it is highly weldable.
- It also has excellent resistance to pitting and cracking.
A. Summary of key differences
The two types of stainless steel are very crucial in the manufacturing industry. The role each one plays is based on its properties. For example, in cases that need to be more prone to corrosion, 316 stainless steel is preferred due to its high corrosion resistance. The low cost of 304 stainless steel also makes it more common than 316.
In the article, we have seen the various differences between the two types of stainless less. Also, in order to choose the right type of stainless steel to use, one can result in use of rapid prototyping. Some of these prototyping methods include CNC machining and injection molding. These processes involve the formation of prototypes to assess the efficiency of the two materials before mass production. The first process involves mold manufacturing whereby molds are formed in reference to the required mold designs and the mold is used in the production process to shape the product into its desired shapes and features. After the whole product solidifies into the prototype of the end product, the manufacturer gets to test the various environments favorable and unfavorable to the product before producing more products for the public. The differences are not physical and therefore the two might seem to look the same making one think that they are all of one kind. That is why testing and determining their different non-physical differences is advisable.
B. Importance of selecting the right stainless steel for specific applications
It is very important to learn about their different features as each has areas they are best suited for. Knowing their differences also helps to know their difference in prices and availability. For efficiency in the production process and performance of various equipment, it is necessary to know which type of stainless steel to use and how to use it.