Improving Steel Strength and Corrosion Resistance (laser cutter cnc Barton)
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Alloy Steels vs Stainless Steels
When it comes to high strength steels, alloy steels and stainless steels are common options. But which provides better strength and corrosion resistance?
Alloy steels are made by adding alloying elements like chromium, nickel, manganese, and vanadium to improve properties like hardness, tensile strength, and toughness. Higher carbon alloy steels offer strength but low corrosion resistance. Stainless steels contain at least 10.5% chromium which forms a protective oxide layer preventing corrosion. While stainless steels offer excellent corrosion resistance, high alloy steels generally provide greater strength.
For applications where both strength and corrosion resistance are needed, precipitation hardening stainless steels like 17-4 PH offer a good compromise. The 17-4 PH stainless steel combines high strength up to 190 ksi yield strength after precipitation hardening heat treatment along with good corrosion resistance from its stainless steel composition.
Removing Chrome from Steel
While chromium improves corrosion resistance, some applications require removing the chrome layer from stainless steel. How can chrome be removed?
Chrome Plating Removal
Chrome plating is commonly applied to steel parts for decoration, wear resistance, or corrosion protection. To remove chrome plating, a chemical bath using sulfuric acid and other chemicals dissolves the chrome layer which can then be rinsed off. This avoids damage to the base metal.
Removing Scale
At the high temperatures of welding and heat treating, chromium oxide forms on the steel's surface as scale. To remove this tough scale, abrasive blasting is an effective method. Sandblasting steel with aluminum oxide or silicon carbide abrasive can efficiently remove the chromium oxide scale.
Passivation
Passivation is the process of removing free iron from the surface of stainless steels. Nitric acid or citric acid baths are commonly used. Passivation enhances stainless steel's natural corrosion resistance.
Electropolishing
Electropolishing uses an electrolytic bath to remove surface metal and smooth stainless steel parts. It also makes the steel passive by enriching the chromium at the surface. Combining corrosion resistance with a smooth finish makes electropolishing ideal for stainless steel parts in hygienic environments.
Pickling
Pickling involves soaking steel in acids like hydrochloric acid or sulfuric acid to remove scale and surface defects. This cleaning process removes contamination but can also etch the surface.
Conclusion
Understanding the properties and best uses of different steels allows choosing the right steel composition for the application, whether for strength like alloy steels or corrosion resistance such as stainless steels. Processes like abrasive blasting, passivation, and electropolishing can then remove chrome if required to prepare the steel parts for service. With the right knowledge, today's high performance steels can be machined into durable components ready to meet the challenges demanded.
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Improving Steel Strength and Corrosion Resistance CNC Milling