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Carbon Steel

Carbon steel refers to steel whose strength and other mechanical properties depend on the amount of carbon in it. It usually has little alloy added. It is also called plain carbon steel or carbon structural steel. It is an iron-carbon alloy with less than 2% carbon. Besides carbon, it also has small amounts of silicon, manganese, sulfur, and phosphorus.

By how it is used, carbon steel divides into three types: carbon structural steel, carbon tool steel, and easy-cut structural steel. The carbon structural steel divides into construction steel and machinery manufacturing steel. Based on how it was made, it can be open-hearth steel, converter steel, or electric-furnace steel. By how it was de-oxidised, it includes rimmed steel (F), killed steel (Z), semi-killed steel (b), and special killed steel (TZ).

By how much carbon it has, carbon steels are low-carbon steel (≤ 0.25%), medium-carbon steel (0.25–0.6%), and high-carbon steel (> 0.6%). By how much phosphorus and sulfur it has, carbon steels are ordinary carbon steel (higher P, S), high-quality carbon steel (lower P, S), superior carbon steel (still lower P, S), and extra-superior carbon steel (very low P, S). Generally, more carbon means higher hardness and strength but lower ductility and toughness.

Stainless Steel

Stainless steel means steel that resists rust and corrosion. It refers to steel that resists air corrosion and acid corrosion. It is a high-alloy steel with over 60% iron plus elements like chromium, nickel, and molybdenum. When chromium is more than 12%, the steel resists air and weak nitric acid corrosion because the chromium forms a dense film of chromium oxide on the surface.

Even though stainless steel usually has over 14% chromium, it still may rust. In coastal or very polluted areas where there are many chloride ions in the air, the surface may get rust spots. These spots stay on the surface and do not harm the inside of the steel body.

In steel with over 12% chromium you get stainless properties. By microstructure after heat treatment, stainless steels split into five types: ferritic, martensitic, austenitic, duplex (austenitic–ferritic), and precipitation-hardening stainless steels.

1. Ferritic Stainless Steel – It has 12–30% chromium. It gives good corrosion resistance, toughness, and weldability. It also resists chloride stress corrosion better than other types.

2. Austenitic Stainless Steel – It has over 18% chromium, about 8% nickel, and small amounts of molybdenum, titanium, and nitrogen. It gives good overall performance and resists many corrosive environments.

3. Duplex Stainless Steel – It has both austenitic and ferritic structures. It has higher strength and corrosion resistance.

4. Martensitic Stainless Steel – It has high strength but lower ductility and worse weldability.

Application in Stainless Steel Wire Ropes

Stainless steel—especially grades like AISI 304 and 316—is often used to make wire ropes for marine, building, and industrial uses. These wire ropes have strength and resist corrosion at the same time. They last a long time in tough environments like offshore or humid places. The film of chromium oxide on the surface helps protect the rope from rust. The nickel and molybdenum help resist acids and chlorides.

Tianli Metal offers high-quality stainless steel wire ropes that show the best features of these alloys—strength, flexibility, long life in hard conditions.

The corrosion resistance of stainless steel generally improves as the chromium content increases. The underlying mechanism is that when steel contains sufficient chromium, a very thin and dense oxide film forms on its surface, which effectively prevents further oxidation. In oxidizing conditions this protective film is reinforced, while in reducing environments it can be disrupted—leading to corrosion.

Which kinds of stainless steel are less likely to rust?
There are three main factors that influence the corrosion resistance of stainless steel:

1. Alloying element content
In general, when the chromium content of steel reaches about 10.5 %, it begins to exhibit stainless behaviour.  In alloys with higher chromium and nickel content, the corrosion resistance becomes even better. For example, in grade 304 stainless steel the nickel content is about 8-10 % and chromium is about 18-20 %, which under ordinary conditions means such steel will not easily rust. 

Stainless steel refers to steel that is resistant to corrosion by air, steam, water and other weak corrosive media, as well as chemical immersions such as acids, alkalis and salts. It is also called corrosion-resistant acid steel. In actual use, steel that resists weak corrosive media is commonly called stainless steel, whereas steel that resists chemical medium corrosion is called acid-resistant steel. Because the two differ in chemical composition, the former does not necessarily resist chemical medium corrosion, while the latter generally has stainless behaviour.