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introduction of AISI4140 steel plate
AISI4140 steel belongs to ultra high strength steel, with high strength and toughness, small deformation during quenching, good hardenability, no obvious temper brittleness, high fatigue limit and multiple impact resistance after quenching and tempering treatment, good low temperature impact toughness.The steel is suitable for manufacturing requires a certain strength and toughness of large and medium-sized plastic mold, such as locomotive traction with the big gear, the supercharger drive gear, pressure vessel, rear axle, gear load connecting rod and a spring clip, can also be used to under 2000 m deep well of oil drill pipe joint and the fishing tool, and can be used for bending machine mould, etc.
AISI4140 is also alloy structural steel, also known as alloy steel, is to add alloy elements on the basis of carbon structure, the first is to improve the hardenability of steel, ensure steel after heat treatment to obtain good comprehensive mechanical properties, with high strength and enough toughness.With suitable hardenability, after appropriate metal heat treatment, the microstructure is homogeneous sorbite, bainite or very fine pearlite, thus has higher tensile strength and showed (around 0.85), high toughness and fatigue strength, and low ductile to brittle transition temperature, can be used in the manufacture of section size larger machine parts.
Ii. AISI4140 implementation standards and technical requirements
AISI4140 standard: wjx039-2005.
AISI4140 technical requirements: flaw detection, z15-z35 thickness direction performance requirements, high strength and high toughness requirements.
Iii. Delivery time of AISI4140
Delivery status: hot rolling, controlled rolling, normalizing, annealing, high temperature tempering, etc.
Delivery time: normalizing (50 days), high-temperature tempering (50 days), unnormalizing (25 days), and annealing (50 days).
4. Chemical composition of AISI4140
Carbon (C) manganese (Mn) phosphorus (P) sulfur (S) nickel (Ni) chromium (Cr)
0.38 ~ 0.43 0.75 1.00 0.030 0.040 0.030 or less or less or less 0.80 ~ 1.10
5. Mechanical properties of AISI4140
Tensile strength b (MPa) yield strength s (MPa) elongation 5 (%) section shrinkage (%) impact energy Akv (J) impact toughness value kv (J/cm2) hardness
1080(110) 930(95) 12 45 63 78(8) 217HB
Vi. Role of alloying elements in AISI4140
Increase the hardenability of steel.Hardenability refers to the depth at which the martensite layer is quenched from the surface during the quenching of steel, and is the main parameter for obtaining good comprehensive properties.In addition to Co, almost all alloying elements such as Mn, Mo, Cr, Ni, Si, C, N, B, etc. can improve the hardenability of steel, among which Mn, Mo, Cr, B have the strongest effect, followed by Ni, Si, Cu.However, strong carbide forming elements such as V, Ti, Nb, etc. can only increase the hardenability of steel when dissolved in austenite.
Influence the tempering process of steel.Due to the alloy elements on tempering can hinder the diffusion of atoms in steel, and compared under the same temperature and carbon steel, general rise to delay the decomposition of martensite and carbide gathered grew up effect, so as to improve the tempering stability of steel, namely improve steel tempering softening resistance, V, W, Ti, Cr, Mo, Si effect is more significant, the effect of Al, Mn, Ni is not obvious.Contain higher content of carbide forming elements such as V, W, Mo, such as steel, during 500 ~ 600 ℃ tempering, precipitate fine dispersion of special carbide particles such as V4C3, Mo2C and W2C, replace part of the relatively bulky alloying cementite, decrease the strength of the steel is no longer increase, namely a double-dip sclerosis (see drawing).Mo can prevent or weaken the temper brittleness of steel.
(3) the impact of steel strengthening and toughening.Ni strengthened ferrite by solid solution strengthening;Mo, V, Nb and other carbide forming elements improve the yield strength of steel by means of both dispersion hardening and solid solution strengthening.The strengthening effect of carbon is the most significant.In addition, the addition of these alloying elements generally refines the austenite grains and enhances the grain boundary.The factors affecting the toughness of steel are complex, and Ni can improve the toughness of steel.Mn tends to coarsen austenite grains and is sensitive to temper brittleness.Reducing P and S content and improving the purity of steel play an important role in improving the toughness of steel (see strengthening of metal).
Classification of alloy steel plates
1. According to the different heat treatment processes, it can be divided into:
Tempered structural steel: many important parts such as shafts, connecting rods, important bolts, etc., are under a lot of alternating stress and impact load and other complex stress work, so the requirement of high strength and toughness of the comprehensive mechanical properties.In order to meet the above requirements, the steel must undergo quenching and high-temperature tempering treatment (that is, quenching and tempering treatment), quenching and treatment to martensite structure, and then high-temperature tempering to get the sorbite structure.The carbon content of quenched and tempered steel is between 0.3 and 0.5, low carbon content is not easy to harden, and the strength required after tempering is not obtained.High carbon content leads to low toughness and brittle fracture in use.
Surface hardened steel: parts made of a certain hot sheet treatment can be hard wear resistant surface layer and a suitable flexible heart.For example, in order to transfer torque, gear must have enough strength, in the shift process and bear the impact load, but also requires toughness, in the meshing process, gear and bear strong wear and wear resistance, therefore, gear should have high overall strength and "table hard inside tough" performance.
2. According to the heat treatment process, there are:
Carburizing and quenching of low carbon steel: the carbon content is generally between 0.10 and 0.25, so as to ensure the parts of the heart has good toughness.The addition of < 2 chromium, < 4.5 nickel, 2 manganese and 0.001-0.004 boron to the cementitious composite steel for carburizing can improve the hardenability of the steel, the core structure and properties of the parts, as well as the strength and plasticity of the carburized layer.Sometimes also add trace titanium, vanadium and other elements, from refining grain, prevent carburizing when the impact of overheating.
Nitriding treatment: combined steel containing aluminum steel such as 38CrMoAL nitriding steel.Aluminum can be combined with nitrogen to form aluminum nitride, increasing surface hardness and wear resistance.
Surface quenching with high frequency induction heating of carbon steel: alloy structural steel is divided into high quality steel and high quality steel according to the quality of the alloy (add "A" after the steel number);USES are divided into pressure machining (hot pressure machining or cold pressure machining) and cutting steel;According to the state of supply, non - heat treatment, normalizing, annealing or high temperature tempering.
Method for designation of Chinese alloy structural steel
The two Numbers at the beginning of the steel number represents the carbon content of steel, with the average carbon content of several parts per million, the average content of its alloy elements is less than 1.When 50%, only elements are marked in the steel, generally no content is marked, such as 40Cr.The average content is 1.50% ~ 2.49%, 2.50% ~ 3.49%, write 2, 3, etc.If the carbon content is 0.10% ~ 0.17%, chromium content is 0.60% ~ 0.90%, nickel 2.75% to 3.25% steel, 12CrNi3.
Steel vanadium V, titanium Ti, aluminum AL, boron B, RE and other alloy elements, are microalloy elements, although the content is very low, should still be marked in the steel.For example, in 20MnVB steel.Vanadium is 0.07-0.12% and boron is 0.001-0.005%.
High quality steel should be in the steel number at the end of "A", such as 12CrNi3A, super quality steel with suffix "E", such as 12CrNi3E, to distinguish from the general high quality steel.
(4) special purpose alloy structural steel, steel number with (or suffix) represents the use of the symbol.For example, cold heading and cold top forging steel (commonly known as "riveting steel") is prefixed with "ML" (the first letter combination of Chinese pinyin letters of "riveting" and "snail") on the head of the brand.To ensure the Hardenability, the suffix "H" (the first letter of the English word "Hardenability" of "Hardenability" is the same as the symbol commonly used in the world) is added to the end of the brand with steel.The head of the plate shall be prefixed with steel H,, (the first letter of the Chinese phonetic alphabet of "welding").Non-quenched and tempered steel and free-cutting non-quenched and tempered steel shall be prefixed with "F" or "YF" (the first letter or combination of the Chinese phonetic alphabet of "fei" or "yifei") at the head of