20Cr thick-walled seamless steel tube is a grade of steel, which is a low hardenability carbon steel. It is mostly used for manufacturing carbonized parts with high core strength requirements, surface wear resistance, a cross-sectional area below 30mm, or complex shapes with light loads.

20Cr Thick-Walled Seamless Steel Pipe Basic Information

AISI 5120, JIS SCr420, GB 20Cr, DIN 20Cr4 Availability and Hardness: Annealed, Hardness ≤ 179HBS

20Cr Heavy-Wall Seamless Steel Pipe Chemical Composition

Quality Percentage (%)

Carbon C: 0.18～0.24

Silicon (Si): 0.17～0.37

Manganese (Mn): 0.50～0.80

Chrome (Cr): 0.70～1.00

Sulfur (S): Allowable residual content ≤ 0.035

Phosphorus (P): Allowable residual content ≤ 0.035

Nickel (Ni): Allowable residual content ≤ 0.30

Copper (Cu): Allowable residual content ≤ 0.30

Molybdenum (Mo): Allowable residual content ≤ 0.15

20Cr thick-walled seamless steel tube mechanical properties

Trial blank size (mm): 15

Heat Treatment:

One, Quenching Heating Temperature (℃): 880; Coolant: Water, Oil

Second, quenching heating temperature (°C): 780-820; coolant: water, oil

Hardening Heat Treatment Temperature (°C): 200; Cooling Agent: Water, Air

Tensile Strength (σb/MPa): ≥835

Yielding Point (σs/MPa): ≥540

Tensile elongation at break (δ5/%)：≥10

Section reduction rate (ψ/%): ≥40

Impact Absorption Work (Aku2/J): ≥47

Bainite hardness (HBS 100/3000) (in annealed or high-temperature tempered condition): ≤179

Shipment Condition: Goods to be delivered in either heat treated (normalizing, annealing, or high-temperature tempering) or non-heat treated condition. The shipment condition should be specified in the contract.

Key Characteristics of 20Cr Thick-Walled Seamless Steel Pipe

Compared to 15Cr steel, it has higher strength and hardenability, with critical hardenability diameter in oil reaching 4-22mm and in water reaching 11-40mm. However, it has lower toughness, and still tends to grain growth during carburization. Quenching directly after cooling significantly affects impact toughness, thus secondary quenching is required after carburization to enhance the toughness of the core part without brittleness. The steel has high cold deformation plasticity, allowing wire drawing in the cold state. Machinability is good in the state of normalizing or tempering at high temperatures, but is poor after annealing. 20Cr is pearlitic, with good weldability, usually not requiring heat treatment after welding. However, parts thicker than 15mm need to be preheated to 100-150℃ before welding, and can also skip the post-welding tempering treatment.

20Cr Thick-walled Seamless Steel Pipe Process Specification

Standard Temperature: 920-950°C, Hardness: 156-179 HBS

Cold-pressed blank softening processing specifications: Temperature 700~720°C, holding time 8~15h, cooled at a rate of 50~100°C/h, and then air-cooled after furnace cooling. Hardness ≤179HBS before treatment, and ≤140HBS after softening.