17-4 Stainless Steel vs 304: Which is Better

Stainless steel is one of the supreme materials known for its impactful properties in high demanding applications. It has a number of grades which are categorized based on composition and properties. In this article, our focus is on the comparative analysis between 17-4 and 304 stainless steels. Each grade has its own importance in terms of high strength, corrosion resistance, affordability, and longevity, yet to tackle any specified application, precise analysis is preferred. So, despite your profession, this article will provide you with a good understanding as well as a precise comparative analysis for both grades.

17-4 stainless Steel

A grade of stainless steel with a blend of properties such as corrosion resistance, high strength along with exceptional mechanical properties at elevated temperatures. Its other name is SAE type 630 with precipitation-hardening martensitic nature. Furthermore, 17-4 in its name refers to the percentage of chromium, nickel which is 17 and 4 respectively. In addition to this, copper presents in its composition make this material undergo precipitation-hardening that leads to the formation of copper precipitates making it a suitable choice for high strength applications.  Major application for this material includes aerospace components, medical implants, marine equipment along with firearms and weapon components.

Figure 1, 17-4 grade stainless steel.

YouTube link:

https://www.youtube.com/watch?v=Z8l_57vK0nY&pp=ygUNMTctNCBnYXJkZSBzcw%3D%3D

304 Stainless Steel

An austenitic stainless steel that constitutes of chromium, nickel, and iron along with other alloying elements. This specific grade is usually non-magnetic in nature as well as high corrosion resistance. Furthermore, this material can withstand elevated temperatures without altering its properties. Apart from that, it offers ease of fabrication and hygienic properties which allows it to be utilized in a variety of applications including commercial as well as industrial. Major applications for this material include kitchen appliances, food processing equipment, architectural, automotive, and other industrial components [5] [6].

Figure 2, 304 grade stainless steel.

YouTube link:

https://www.youtube.com/watch?v=7T4GvUNUWxQ&pp=ygUMMzA0IGdhcmRlIHNz

What is the Difference Between 17-4 Stainless Steel and 304?

Both grades can be distinguished among each other based on several factors that are mentioned below one by one:

Chemical Composition

Table 1, Chemical composition 

Mechanical Properties

Table 2, Mechanical properties

Machinability

17-4 grade stainless steel:

The mechanical properties of this material, especially high strength along with good hardness does not allow it to be machined easily rather it requires special technique and tools for avoiding excessive wear problems. Furthermore, the surface finishing for this material depends on the application requirements in term of corrosion resistance and aesthetic look.

304 grade stainless steel:

This specific grade of stainless steel has exceptional machinability particularly in annealed conditions. Apart from that, this grade steel also contains good surface but eventually the quality depends on the need for specific application.

Weldability

17-4 grade of SS due to its precipitation-hardening nature is poor for welding purposes and may require treatment before and after welding to avoid the risk of cracking. In contrast, 304 grade SS has exceptional weldability and has the ability to weld via several techniques.

Flatness and Stability

The flatness and stability of stainless steel depends on the process used for manufacturing as well as the heat treatment processes it undergoes but since we are concerned about 17-4 and 304 grades of stainless steel, both are favorable for applications demanding stability and precision but 17-4 has more stability than 304 due to the properties including high strength and good hardness.

Corrosion Resistance

Both grades of stainless-steel offer adequate amount of resistance against corrosion due to the presence of chromium in their compositions. On precise comparative analysis, it is observed that 17-4 grade offer better resistance to corrosion in case of chloride-induced stress corrosion cracking while 304 grade shows resistance against pitting, oxidation as well as crevice corrosion which are the general forms of corrosion.

Summary Chart of Aluminum 6061 t6 and t651 Properties

Table 3, Properties of Al 6061-T6 and 6061-T651

Advantages and disadvantages 17-4 Stainless Steel and 304

17-4 Stainless Steel:

Figure 3, Pros and cons of 17-4 grade SS

304 Stainless Steel:

Figure 4, Pros and cons of 304 grade SS

Which Alloy is Better for Your Precision Machining Needs?

In order to make an effective decision for alloy that is better in precise machining needs, you need to figure out the certain application that demands such precision. However, there are several factors based on which it can be decided. These factors are listed below:

• Machinability
• Material properties
• Corrosion resistance
• Cost
• Surface finish

Based on the above-mentioned factors along with the application chosen, it will be easy to select which alloys is better, yet you can’t decide directly based on assumptions.

Examples of Precision Machining Applications

17-4 Stainless Steel:

• Aerospace Industry
• Chemical Processing Industry
• Oil and Gas Industry

Figure 5, Application of 17-4 stainless steel

304 Stainless Steel:

• Automotive Industry
• Construction Industry
• Food Processing Industry

Figure 6, Application of 304 stainless steel