What Is Q235NH Weathering Steel
Q235NH is a weather-resistant structural steel per GB/T 4171, commonly known as corten steel. It is made from ordinary carbon steel with small amounts of copper, nickel, and other corrosion-resistant elements added, giving it the characteristics of high-quality steel in strength, plastic extension, shaping, welding, cutting, abrasion, high temperature, and fatigue performance. The weather resistance is 2 to 8 times that of ordinary carbon steel.
How the Protective Patina Works
In atmospheres containing moisture and pollutants, the alloying elements promote the formation of a dense, adherent rust layer on the surface. This patina blocks oxygen and moisture from reaching the base metal, so the corrosion rate drops dramatically after the initial exposure period. The self-limiting oxide layer regenerates after surface damage, giving long service life without painting.
Chemical Composition
Per GB/T 4171, Q235NH limits carbon to 0.13 percent, silicon to 0.10 to 0.40 percent, manganese to 0.20 to 0.60 percent, phosphorus to 0.030 percent, and sulfur to 0.030 percent, with copper 0.25 to 0.55 percent and chromium and nickel additions for the corrosion resistance mechanism.
Mechanical Properties
The yield strength is 215 to 235 MPa, the tensile strength 360 to 510 MPa, and the minimum elongation 23 percent for thicknesses up to 16 mm, with the values defined by the thickness range in GB/T 4171.
Applications
Q235NH is widely used in containers, power plant chimneys, railway engineering, and other outdoor steel structures, where the rust-resistance, anti-corrosion, and life extension of components, plus thinning, consumption reduction, and labor and energy savings, deliver economic benefits. For load-bearing structures requiring higher strength, the Q355NH and Q460NH grades are used.
Frequently Asked Questions
Q: What does Q235NH stand for?
A: Yield strength of 235 MPa, N for weathering, H for high atmospheric corrosion resistance per GB/T 4171.
Q: How much better is the corrosion resistance?
A: 2 to 8 times that of ordinary carbon steel.
Q: Does it need painting?
A: No, the patina protects the base metal.
Q: What is the yield strength?
A: 215 to 235 MPa depending on thickness.
Q: What are the main uses?
A: Containers, chimneys, railway engineering, and outdoor structures.
Q: What higher-strength grades exist?
A: Q355NH and Q460NH.
For Q235NH weathering steel quotations, contact our sales team.