The Grade Guide: 17-4 (630) Grade Martensitic Stainless Steel
Stainless steel comes in a variety of grades and compositions. It is essential to consider your final application for the material in order to select the correct type and grade of stainless steel.
We have covered 300 series and 400 series stainless steels in prior blogs.
This blog is dedicated to 17-4 PH.
The Main Grades of Stainless Steel
Austenitic, ferritic, martensitic, duplex, and precipitation-hardening are the main types of stainless-steel alloys. Their differences are based on their distinct microscopic crystalline structures, each of which lends the steel a specific metallurgical profile.
The most widely used stainless steel is austenitic, with the 300 series being the most popular grade. At Certified Grinding & Machine, 303 Stainless Steel is our most popular grade; our second most popular grade is 416, martensitic stainless steel. 630 is also a popular grade of material.
Competition Series: 300 vs. 400
One of the key differences between 400 and 300 series stainless steels is the 400 series stainless steels can be hardened and tempered through heat treating. The 400 series has limited formability and weldability.
The benefits of 300 series stainless steels are its corrosion resistance and its high ductility. The benefits of 400 series are its increased hardness capability through heat treatment and its strength. In most situations 17-4 material is heat treated to a higher hardness prior to grinding and machining.
The Specifics of Type 17-4
Type 17-4 is the most common grade of martensitic precipitation hardenable (PH) alloys. 17-4 provides an outstanding combination of high strength, good mechanical properties at temperatures up to 600°F (316°C), and short-duration, low-temperature heat treatments that minimize warpage and scaling.
Its good corrosion resistance, formability and weldability make it ideal for a variety of applications in aerospace, petrochemical, and other structural applications. In the annealed condition 17-4 maintains high mechanical properties, making some forming operations difficult.
Preconceived Notions Regarding Pre-Hardening
17-4PH can be a complicated material to specify and purchase. Many people think that this material is a pre-hardened material with a high Rockwell C rating due to the PH in the material designation.
This is not true since it is annealed after being solution hardened. 17-4 can be purchased or heat treated to several different hardness levels depending on the customer’s requirements. Please refer to the table below for some actual data on the different 17-4 treatments and their effect on hardness, tensile strength and other physical characteristics:
We have the experience and knowledge to help you select the correct grade of stainless steel for your part. Our team will work with you to understand yourfinal application and troubleshoot any process issues you may encounter.
Have questions about which stainless steel grade is right for you? Contact us today.