They have certain differences in organization, heat treatment process, properties and uses. The following is a detailed comparison of these four stainless steels:
I. Chemical composition
12Cr13: The main components are carbon (C) 0.09-0.15%, chromium (Cr) 11.50-13.50%, and a small amount of silicon (Si), manganese (Mn), phosphorus (P) and sulfur (S).
20Cr13: The chromium (Cr) content is about 20%, the carbon (C) content is about 0.13%, and it also contains a small amount of other elements.
30Cr13: Contains a higher chromium (Cr) content, as well as appropriate amounts of carbon (C), nickel (Ni), manganese (Mn), silicon (Si), phosphorus (P) and sulfur (S).
40Cr13: The content of chromium (Cr) and carbon (C) is high, and it has the highest hardness among the four materials.
2. Organization and heat treatment
12Cr13: It is a semi-martensitic steel. After quenching and high-temperature tempering, it has high strength, toughness and good corrosion resistance.
20Cr13: It is also a martensitic stainless steel. Its heat treatment performance is similar to that of 12Cr13, but its strength and hardness are slightly higher, and its toughness and corrosion resistance are slightly lower.
30Cr13: It has higher strength, hardness and hardenability after quenching, and is suitable for occasions requiring high strength and high hardness.
40Cr13: Its hardness and wear resistance can be further improved by heat treatment. It has the highest hardness among the four materials.
3. Performance characteristics
Corrosion resistance: All four materials have good corrosion resistance, but the specific corrosion resistance varies depending on the chromium content and other alloying elements. Generally speaking, the higher the chromium content, the better the corrosion resistance.
Strength and hardness: From 12Cr13 to 40Cr13, the strength and hardness of the material gradually increase with the increase of chromium and carbon content. Among them, 40Cr13 has the highest strength and hardness, but relatively low toughness and corrosion resistance.
 Processing performance: All four materials have good processing performance, but the specific processing difficulty may vary due to the hardness and toughness of the materials.
IV. Uses
12Cr13: Mainly used to manufacture parts that require high toughness, certain stainlessness and withstand impact loads, such as turbine blades, fasteners, hydraulic press valves and thermal cracking anti-sulfur corrosion equipment.
20Cr13: Mainly used to make parts that withstand high stress loads, such as turbine blades, hot oil pump shafts and sleeves, impellers, etc. At the same time, it is also used in the papermaking industry, medical equipment and household appliances.
30Cr13: Due to its excellent corrosion resistance, strength and hardness, it is widely used in many fields such as kitchenware manufacturing, medical equipment, mechanical parts, architectural decoration and automotive accessories.
40Cr13: Mainly used to manufacture knives, mechanical accessories, bearing parts and other parts that require high hardness and wear resistance.
In summary, 12Cr13, 20Cr13, 30Cr13 and 40Cr13 have certain differences in chemical composition, organization and heat treatment, performance characteristics and uses. When choosing to use, the appropriate material should be selected according to the specific application scenario and needs.