Grade 20# steel
The 20# steel refers to a  ↑÷carbon content of 0.2%, whi&β<<ch is a low-carbon steel. Ste♣♠♥el can be divided into low ca↓®π∞rbon steel, medium carbon steel≤£♦ and high carbon steel. ↕ →

Carbon content: low carbon ste∏∑★→el is generally less§≥$ than 0.25%; medium carbon ♦☆steel is generally between 0.☆≥25 and 0.60%; high carbon ₹δ♦steel is generally greater than 0.60®₽%.
In addition to the carbon€φ✘ (C) element and a certain amount of £₽silicon (Si) (generally no more←≤ than 0.40%) and manganese (Mn) (​&generally no more than 0.80%, 'ααup to 1.20%) alloy elemenφ>ts in steel for deoxida∏βtion, No other alloying elements (e↑♣φxcept residual elements).
Usually called wrought iron with a carb§©★on content of less tha₹ γn 0.02%, pig iron witβγσ→h a carbon content of more than 2.★∏​11% to 4.3%, and steel φγπεin the middle.
Chinese name No. 20 steel standard ♥∞σ<GB/T 699-2015 carbon cont£‍¶ent 0.2% category low carbon st✘♣eel
contents

characteristic
(1) Features The steel belong★•λ‌s to high-quality lowβσ-carbon carbon steel, cold-ext¥®ruded, carburized and hard→₹δ≈ened steel. The steel has low strengt×¥ ×h, good toughness, plas≠₹ ticity and weldability. The tensile s‌€☆εtrength is 253-500MPa, and the ↕≈elongation is ≥24%.
The properties of 20 are ♠"♠basically similar to ‍ those of 15 steel, but the str≈∞λength is slightly higher. Us☆¥®es: suitable for the manufacture o¥→↓×f small and medium-si±§<£zed carburizing and c€₩♦₽arbonitriding parts tha™®‌t are not important fo∞£γr the construction of automobi ↔↕les, tractors and general machiπ♣φ‍nery manufacturing, such as hand​π" brake shoes, lever shaft≈ s, gearbox speed forks, tra™γσnsmission passive gears and Camshafts o≠ ♥n tractors, suspensio€ n equalizer shafts, equalizer inner an¥↔≠ d outer bushings, etc.; used t§™∑o manufacture various mechanical‌ Ω± parts that are not stres≈¶©©sed but require high toughness under h←•$βot-rolled or normalized conditions; i≥≥n heavy and medium-s§★∞λized machinery manufacturi♠‍&¶ng Medium, such as forg$ ed or pressed tie rods, shaπ σckles, levers, sleeveσ₽π✘s, clamps, etc. In tβ‍he steam turbine and boiler manufactur©Ωing industry, it is mostly u♣✔sed for pipes, flanges, headeλ σrs and various fasten↔≈Ω"ers working in non-corrosiv₹‌e media with pressure ≤ 6N/squa"€≈γre and temperature ≤ 450 ℃; used to≈  make crosses on railways, locomotives ™©and vehicles Castings suc¶₽↔$h as heads and pistons.
Normalizing can prom&β↑™ote the spheroidization of §£the steel, refine the massive proeutectγ₹☆oid ferrite, and improve t÷§←‍he cutting performance ofσ< the blank less than 160HBS.
The process route of the steel ♣✘mold parts is: blanking→forging d'→↕ie blank→anneali←Ωng→mechanical rough machini®¥Ωng→cold extrusi₩α€on molding→recrystallizati♣≥βon annealing→mechanicaφ α&l finishing→carburizing&ra  rr;quenching, tempering&rarr÷®;grinding and polishing→assem‌§←≤bly.
(2) Delivery state and ¶λ≈ hardness Unheated state, hardness &le₹≠♦®;156HBS.
chemical composition
(3) The chemical composition of standaΩ★rd JB/T 6057-92 steel (mass fraction,£✘ %)

(4) Refer to the corresponding stee​σε₽l grade. The standard st✘δeel grade of my country’s  δ÷GB/JB is 20, my country’s TaΩαiwan CNS standard ste♣✔₩el grade S20C, German ↓®DIN standard material number 1.040¶≥2, German DIN standard steel©₹®" number CK22/C22, British ≈♠BS standard steel number IC2✔π2, France AFNOR stan∞★♠dard steel number CC20, French NF stan€δππdard steel number C22, Italian UNI st≥δ®₩andard steel number C20/C21, Belgium '&∞NBN standard steel number C25-1, → Sweden SS standard steel numbe∑≤∞r 1450, Spain UNE standard steel$ " number F.112, American AISI/ S" ∞®AE standard steel number 1020, Japanes∑​e JIS standard steel number‍₩∞≤ S20C/S22C.
Mechanical properties
(5) Phase transition temperature (ap♠÷‌proximate value) Ac1=735℃, Ac3=855€ε ℃, Ar3=835℃, Ar1=680℃
(6) Normalizing specifi₹€cation The temperature is 920~950℃∏σ¥, and the furnace is air-coole→£≈£d. The hardness is 131~156HBS.
(7) Specification for softening tr¶♥<eatment of cold-pressed blanks The temp≤δ®'erature is 700~720℃, the holdiΩ ¥ng time is 8~15h, and the cooling₹☆ rate is 50~100℃/h, and the temperature∑Ω♣ is lowered to 550~600℃ with the f‍★urnace, and the furnace is air-coole♣♠Ωd.
The hardness before treatment is less ​  than or equal to 143HBS, and the∑∏÷' hardness after softening is ‌∞☆less than or equal to 131H±✘BS.
(8) Quenching specification Temperat&€ure 910℃±10℃, cooling with←☆∞ 10% NaCl brine.
(9) Measured yield strength fy= ‍γ245Mpa, elastic modulus E=20¶€®★6Gpa, Poisson’s ratio ν=0.3.
(10) The shear strength is  π♦¥275~392MPa, the tensile strength is 25φ≈3~500MPa, the yield strength is 275MPa,§‌​ and the elongation is 25%.
(11) The annealing temperature ​↑is only 600-650 degr≈&‌ees, and the holding≠≥♣® time is 1-2h.

Allowable stress of No. 20 ☆®®Ωsteel at 225℃: (16-36mm) betw&€een 111-124MPa; (6-16mm) ≤λbetween 117-131MPa
Allowable stress of No. 20 s✘←teel at 100°C: at 1​♠>₩50°C, the allowable ♥≥±stress of No. 20 steel pipe is 13₩ >$0 MPa, and that of No. 20 sλβteel forgings is 108 MPa

Both steels are low-α"±carbon steels. From the data Ω₹$point of view, the carbon conten♠♠©t of No. 20 steel is slightly higher,β✘€≠ and the metallographic structure ↓₽↓of both is pearlite + ferrσ'>©ite. The performance reflected in theφ→  performance is that the tensile strengβ♦®§th and impact toughnes≤÷s of the 20 steel are sli×÷₽★ghtly higher, and basically‍" there is no big diffε¶εerence between the t‍∞wo steels. Both steels cannot©÷↑ be quenched, and the heat treatment p¶¥£∏rocess is relatively simple. ★ "Usually the blank is directly cut o←→ r forged and normalized, used ∑∑for unimportant structu ∑ral parts, connecting paΩφrts or stamping parts, or use♥¶d as carburizing steel. No. 1∞↓γ<5 steel seems to be found on the mark←×δ∑et, and it can be repl↓↕↓¥aced with 20 steel.