Round Bar S45c

Round bar s45c

45# is the grade of steel is a high-quality carbon structural steel, corresponding to Japanese standard S45C, American standard: 1045, German standard C45. It is characterized by higher strength and deformation resistance than ordinary A3 steel.

Chinese name 45 steel plate

foreign name carbon steel

δ5\%≥16

Common thickness 0.5-80 mm

Material density 7.85g/cm³

GB/T 699-1999

σb ≥600MPa

σs ≥355MPa

Chemical composition Element ratio (%) :

Carbon C:0.42 ~ 0.50;

Chromium Cr: ≤0.25;

Manganese Mn: 0.50 ~ 0.80;

Nickel Ni: ≤0.25;

P: ≤0.035;

Sulfur S: ≤0.035;

Silicon Si: 0.17 ~ 0.37

Mechanical property

Sigma b \ MPa: p. 600

Sigma s \ MPa: p. 355

The delta \ % 5:16 or higher

Bits of \ % : 40 or higher

Hardness \HB:≤197

The recommended heat treatment temperature of 45 steel stipulated in GB/T699-1999 standard is 850℃ normalizing, 840℃ quenching, 600℃ tempering, and the performance is ≥355MPa yield strength

The GB/T699-1999 standard stipulates that the tensile strength of 45 steel is 600MPa, the yield strength is 355MPa, the elongation is 16%, and the section shrinkage is 40%

45# (No.) steel and 40Cr steel tempering heat treatment process

Tempering is a double heat treatment of quenching and high temperature tempering, the purpose of which is to make the workpiece have good comprehensive mechanical properties.

Tempered steel has carbon tempered steel and alloy tempered steel two categories, whether carbon steel or alloy steel, its carbon content control is more strict. If the carbon content is too high, the strength of the tempered workpiece is high, but the toughness is not enough, such as the carbon content is too low, the toughness is improved and the strength is insufficient. In order to obtain good comprehensive performance of the tempering parts, the carbon content is generally controlled at 0.30~0.50%.

During quenching and tempering, the whole section of the workpiece is required to be quenched, so that the workpiece can obtain the micro-structure dominated by fine needle-quenched martensite. The microstructure of uniformly tempered sorbite was obtained by high temperature tempering. Small factories can not engage in metallographic analysis of each furnace, generally only hardness test, that is, the hardness after quenching must reach the hardness of the material, the hardness after tempering according to the requirements of the diagram to check.

The operation of the workpiece tempering treatment must be carried out strictly in accordance with the process document, and we just give some views on how to implement the process in the operation process.

1, the conditioning of 45 steel

45 steel is a medium carbon structural steel, hot and cold processing performance is good, good mechanical properties, and low price, wide source, so widely used. Its biggest weakness is low hardenability, large cross-section size and relatively high requirements of the workpiece should not be used.

The quenching temperature of No. 45 steel is A3+(30~50) ℃, and in actual operation, the upper limit is generally taken. High quenching temperature can accelerate the heating speed of the workpiece, reduce surface oxidation, and improve the work efficiency. In order to homogenize the austenite of the workpiece, sufficient holding time is required. If the actual amount of furnace loading is large, it is necessary to appropriately extend the holding time. Otherwise, there may be insufficient hardness due to uneven heating. However, if the holding time is too long, there will also be coarse grains, serious defects of oxidation and decarburization, which will affect the quality of quenching. We believe that if the furnace loading is greater than the requirements of the process document, the heating and holding time should be extended by 1/5.

Because of the low hardenability of No. 45 steel, a 10% brine solution with a large cooling rate should be used. After the workpiece enters the water, it should be quenched, but not cold, if the workpiece is cold in salt water, it is possible to crack the workpiece, because when the workpiece is cooled to about 180 ° C, the austenite is rapidly transformed into martensite, resulting in excessive organizational stress. Therefore, when the quenched workpiece is quickly cooled to the temperature area, the method of slow cooling should be taken. Because the temperature of the water is difficult to master, it must be operated by experience, when the workpiece in the water stops shaking, the water can be air-cooled (such as oil cooling is better). In addition, the workpiece should be moved into the water should not be static, should be in accordance with the geometric shape of the workpiece, make regular movement. The static cooling medium coupled with the static workpiece leads to uneven hardness, uneven stress and large deformation of the workpiece, and even cracking.

The hardness after quenching of 45 steel tempering parts should reach HRC56~59, and the cross-section may be lower, but not lower than HRC48, otherwise, it means that the workpiece has not been fully quenched, and there may be sostenite or even ferrite organization in the organization, which is still retained in the matrix through tempering, and can not achieve the purpose of tempering.

The high temperature tempering after quenching of No. 45 steel, the heating temperature is usually 560~600℃, and the hardness requirement is HRC22~34. Because the purpose of conditioning is to obtain comprehensive mechanical properties, the hardness range is relatively wide. However, if the drawings have hardness requirements, the tempering temperature should be adjusted according to the requirements of the drawings to ensure hardness. If some shaft parts require high strength, high hardness requirements; And some gear, with the keyway of the shaft parts, because of the quality after milling, insert processing, hardness requirements are lower. Regarding the tempering holding time, depending on the hardness requirements and the size of the workpiece, we believe that the hardness after tempering depends on the tempering temperature, which has little relationship with the tempering time, but must be back through, the general workpiece tempering holding time is always more than one hour.

Specific application

No. 45 steel is widely used in machinery, without heat treatment: HB≤229; Heat treatment: normalizing; Impact power: Aku≥39J; High strength, plasticity and toughness is still good, 45# steel quenched before no tempering, hardness greater than HRC55 (up to HRC62) is qualified, after heat treatment, and then tempering can reach HRC42-46, so that it can ensure its good mechanical properties, but also get the surface hardness requirements, It is used to make small section tempering parts with large load and large normalizing parts with small stress, as well as surface quenched parts with low core strength requirements, such as pins, guide posts, watch hands and other parts.

Identification type

1. Often by grinding with a grinding wheel, see the sparks, white is high carbon steel, such as 45 steel, red is A3 steel.

2. The material of 45 steel and Q235 is ground on the stone, and Q235 is easily ground off.

3. With a hammer, the mark of 45 steel is much shallower than the mark of Q235(A3), because Q235 is much softer than 45 steel.

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