Who can tell me the difference between 450 steel and 45 steel in terms of structural composition and physical and chemical properties?

No.45 steel is the name in GB, called S45c in JIS,1045,080m46, called C45 in DIN ASTM. In China, it is often called No.45 steel, also known as "oil steel". In general, spot hot rolling is the majority in the market. The cold rolling specification is between1.0 ~ 4.0 mm.

Edit the chemical composition of this paragraph.

Carbon (C) content is 0.42-0.50%, silicon content is 0. 1.7-0.37%, manganese content is 0.50-0.80%, and chromium content is 0.

Edit this paragraph processing method

heat treatment

Recommended heat treatment temperature: normalizing 850, quenching 840 and tempering 600. 45 steel is a high-quality carbon structural steel, which is not hard and easy to cut, and is often used as 45 steel pipe in dies.

Template, pin, guide post, etc. But it needs heat treatment. 1.45 steel with hardness greater than HRC55 (reaching HRC62) before tempering after quenching is qualified. The highest hardness in practical application is HRC55 (high frequency quenching HRC58). 2.45 steel should be carburized and quenched. Quenched and tempered parts have good comprehensive mechanical properties and are widely used in various important structural parts, especially those connecting rods, bolts, gears and shafts that work under alternating loads. But the surface hardness is low and it is not wear-resistant. The surface hardness of parts can be improved by tempering and surface quenching.

carbonize

It is generally used for heavy-duty parts with wear-resistant surface and impact-resistant core, and its wear resistance is higher than tempering+surface quenching. Its surface carbon content is 0.8- 1.2%, and the core is generally 0. 1-0.25% (0.35% in special cases). After heat treatment, the surface can obtain high hardness (HRC 58-62), and the core has low hardness and impact resistance. If 45 # steel is carburized, hard and brittle martensite will appear in the center after quenching, and the advantages of carburizing treatment will be lost. At present, the carbon content of materials using carburizing process is not high, and the core strength can reach a high level when it reaches 0.30%, which is rare in application. 0.35% have never seen examples, only introduced them in textbooks. Tempering and high-frequency surface quenching can be used, and the wear resistance is slightly worse than carburizing. According to GB/T699- 1999 standard, the recommended heat treatment system of 45 steel is normalizing at 850℃, quenching at 840℃ and tempering at 600℃, and the achieved properties are yield strength ≥355MPa GB/T699- 1999 standard stipulates that the tensile strength of 45 steel is 600MPa and the yield strength is 600 MPa.

The purpose of editing this paragraph

Function, structural characteristics and technical requirements of shaft parts

Shaft parts are one of the typical parts often encountered in machines. It is mainly used to support the experiment of transmitting zero 45 steel.

Components that transmit torque and bear load. Shaft parts are rotating parts, the length of which is greater than the diameter, and generally consist of the outer cylindrical surface, conical surface, inner hole, thread and corresponding end surface of a concentric shaft. According to different structural shapes, shaft parts can be divided into optical axis, stepped shaft, hollow shaft and crankshaft. A shaft with an aspect ratio of less than 5 is called a short shaft, and a shaft with an aspect ratio of more than 20 is called a slender shaft, with most shafts in between. The shaft is supported by the bearing, and the shaft section matched with the bearing is called the journal. Journal is the assembly benchmark of shaft, and their accuracy and surface quality are generally required. Their technical requirements are generally formulated according to the main functions and working conditions of the shaft, and usually include the following items: (1) journal whose dimensional accuracy plays a supporting role. In order to determine the position of the shaft, higher dimensional accuracy (IT5~IT7) is usually required. Generally, the journal dimension accuracy of assembly transmission parts is low (IT6~IT9). (II) Geometric shape accuracy The geometric shape accuracy of shaft parts mainly refers to the roundness and cylindricity of journal, outer conical surface and Morse taper hole. , its tolerance should generally be limited to the dimensional tolerance. For the inner and outer circular surfaces with high precision requirements, the allowable deviation should be marked on the drawings. (III) Mutual position accuracy The position accuracy requirements of shaft parts are mainly determined by the position and function of the shaft in the machinery. Usually, it is necessary to ensure the coaxiality between the journal of the assembly transmission parts and the supporting journal, otherwise the transmission accuracy of the transmission parts (gears, etc.) will be affected. ) and produce noise. For ordinary precision shafts, the radial runout of the matching shaft section to the supporting journal is generally 0.0 1 ~ 0.03mm, and for high-precision shafts (such as spindles), it is generally 0.001~ 0.005 mm. (4) The surface roughness of the shaft diameter matched with the transmission part is generally Ra 2.5 ~ 0.63 microns, and that matched with the bearing. ..

Blanks and materials of shaft parts

(1) Rough shaft parts Shaft parts can be in the form of bars, forgings, etc. according to the use requirements, production types, equipment conditions and structure. For shafts with similar cylindrical diameters, bars are generally the main ones; Forgings are often used for stepped shafts or important shafts with large cylinder diameters, which not only saves materials, reduces processing workload, but also improves mechanical properties. According to the different production scale, there are two forging methods for blanks: free forging and die forging. Free forging is mostly used in small and medium batch production, while die forging is used in large batch production. (II) Materials of shaft parts: Different materials and different heat treatment specifications (such as quenching and tempering, normalizing and quenching) should be adopted for shaft parts according to different working conditions and use requirements, so as to obtain certain strength, toughness and wear resistance. 45 steel is a common material for shaft parts. The price is low. After quenching and tempering (or normalizing), better cutting performance, higher strength and toughness and other comprehensive mechanical properties can be obtained, and the surface hardness after quenching can reach 45 ~ 52 HRC. Alloy structural steels such as 40Cr are suitable for shaft parts with medium precision and high speed. After quenching and tempering, these steels have good comprehensive mechanical properties. Bearing steel GCr 15 and spring steel 65Mn, after quenching and tempering and surface high-frequency quenching, the surface hardness can reach 50 ~ 58 HRC, which has high fatigue resistance and good wear resistance, so high-precision shafts can be manufactured. The spindle of precision machine tools (such as grinding wheel spindle of grinder and spindle of coordinate boring machine) can be made of 38CrMoAIA nitride steel. After quenching and tempering and surface nitriding, this steel can not only obtain higher surface hardness, but also maintain a soft core, so it has good impact toughness. Compared with carburized and quenched steel, it has the characteristics of small heat treatment deformation and high hardness. 45 # steel is widely used in machinery manufacturing, and its mechanical properties are very good. But this is medium carbon steel, and its quenching performance is not good. 45 steel can be hardened to HRC42~46. Therefore, if the surface hardness is needed and the superior mechanical properties of 45 # steel are expected to be exerted, the surface of 45 # steel is often carburized and quenched, so that the required surface hardness can be obtained. Guojia China Brand No.45. UNS standard number GB 699-88 chemical composition (%) 0.42-0.50c, 0. 17-0.37si, 0.50-0.80mn, 0.035p, 0.035s, 0.25ni, 0.25cr, 0.25cu ingot.

In the field of mold repair

The model of mould welding material for No.45 steel is CMC-E45 No.45 steel welding material.

It is the only medium hardness steel covered electrode with good bonding performance, which is suitable for air-cooled steel and cast steel, such as ICD5, 7CrSiMnMoV…, etc. The repair of stretching parts of automotive sheet metal panel dies and large sheet metal stamping dies can also be used for hard surface production. In addition, there are some points to pay attention to when using: 1. Before construction in wet site, covered electrode should be dried at 150-200℃ for 30-50 minutes. 2. Generally, it should be preheated above 200℃ and air-cooled after welding, and stress relief is best if possible. 3. Where multi-layer surfacing is needed, CMC-E30N can be used as backing, which can get better welding effect. The main component of hardness HRC 48-52 Cr Si Mn C is suitable for current range: diameter and length m/m 3.2*350mm 4.0*350mm Current range (AMP) 70-100130-150.

Classification of steel

Classification by quality

(1) ordinary steel (P≤0.045%, S≤0.050%) stainless steel products.

(2) high-quality steel (both P and S are ≤ 0.035%); (3) advanced high-quality steel (P≤0.035%, S≤0.030%).

Classification by chemical composition

(1) carbon steel: a. low carbon steel (c ≤ 0.25%); B. Medium carbon steel (0.25 ≤ C ≤ 0.60%); C. high carbon steel (C≥0.60%). (2) Alloy steel: A. Low alloy steel (total content of alloying elements ≤ 5%) B. Medium alloy steel (total content of alloying elements > 5 ~ 10%) C. High alloy steel (total content of alloying elements >10%). (3) Combustion can volatilize carbon in steel into carbon dioxide, and the quality of steel samples will be reduced after combustion. However, the mass will increase after combustion. The reason is that iron in steel combines with oxygen to produce ferroferric oxide, and the carbon content is less than that of iron.

Classification by molding method:

(1) forged steel; (2) cast steel; (3) hot rolled steel; (4) cold-drawn steel bars.

Classification by metallographic organization

(1) A. Sub-* * steel (ferrite+pearlite) b.*** steel (pearlite) C. Over-* * steel (pearlite+cementite) D. ledeburite steel (pearlite+cementite). (2) normalizing: a. pearlite steel; B. bainite steel; C. martensitic steel; Austenite steel. (3) No phase change or partial phase change.

Classification by purpose

(1) steel for building and engineering: a. ordinary carbon structural steel; B. low alloy structural steel; C. steel bars. (2) Structural steel A. Steel for machinery manufacturing: (a) quenched and tempered structural steel; (b) Case-hardened structural steel: including carburized steel, ammonia steel and case-hardened steel; (c) free-cutting structural steel; (d) Steel for cold plastic forming: including steel for cold stamping and steel for cold heading. B. Spring steel C. Bearing steel (3) Tool steel: A. Carbon tool steel; B. alloy tool steel; C. high-speed tool steel. (4) Special performance steel: A. Stainless and acid-resistant steel B. Heat-resistant steel includes oxidation-resistant steel, heat-resistant steel and valve steel C. Electrothermal alloy steel; D. wear-resistant steel; E. low temperature steel; F electrical steel (5) professional steel-such as steel for bridges, ships, boilers, pressure vessels, agricultural machinery, etc.

Comprehensive classification

(1) Ordinary steel A. Carbon structural steel: (a) Q195; (b) Q2 15(A、B)； (c) Q235(A、B、C)； Q255(A、B)； Question 275.b. Low-alloy structural steel C. General structural steel for specific purposes (2) High-quality steel (including high-quality steel) A. Structural steel: (a) High-quality carbon structural steel; (b) alloy structural steel; Spring steel; Free cutting steel; Bearing steel; (f) Special-purpose high-quality structural steel. B. Tool steel: (a) carbon tool steel; (b) alloy tool steel; (c) high-speed tool steel. C. Special performance steel: (a) stainless steel and acid-resistant steel; Heat-resistant steel; Electrothermal alloy steel; (d) electrical steel; (e) High manganese wear-resistant steel.

Classification of smelting method

(1) A. Open hearth steel: (a) acidic open hearth steel; Alkaline open hearth steel. B converter steel: (a) acidic converter steel; Alkaline converter steel. Or (a) bottom-blown converter steel; (b) Side-blown converter steel; (c) Top blown converter steel. C. electric furnace steel: (a) electric furnace steel; Electroslag furnace steel; Induction furnace steel; (d) Vacuum consumable furnace steel; (e) electron beam furnace steel. (2) according to the deoxidation degree and pouring system, a. boiling steel; B. semi-killed steel; Killed steel; Special killed steel.