JPH059662A - Steel material for crankshaft of press forging machine - Google Patents

Abstract

PURPOSE:To provide a crankshaft for a press forging machine having a long service life. CONSTITUTION:A steel material for the crankshaft of a press forging machine consisting of, by weight, 0.22-0.32% C, <=0.15% Si, <=0.60% Mn, <=0.020% P, <=0.020% S, 3.25-4.20% Ni, 1.25-2.00% Cr, 0.20-0.60% Mo, <=0.17% V and the balance essentially Fe is prepd. This steel material has remarkably improved shock resistance and improved other mechanical characteristics and the service life is made much longer than that of SNCM439 or SCM440 as a conventional crankshaft material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel material for a crankshaft of a press forging machine.

[0002]

2. Description of the Related Art Conventionally, a crankshaft, which is inserted into a hammer of a press forging machine to move the hammer up and down, has conventionally been a SCM440 (JIS symbol) or SNCM.
Steel types such as 439 (JIS symbol) are mainly used.

[0003]

When the press forging machine is operated, a large impact load is repeatedly applied to the crankshaft that supports the hammer and causes the hammer to move up and down. In the case of a large-sized press forging machine, the impact load applied to the crankshaft is further increased, and further, bending and twisting are added to the extent that cannot be ignored.

Therefore, when the press forging machine is operated for a long period of time, impact fatigue mainly accumulates on the crankshaft, and when the limit is reached, the crankshaft may break from the root of the pin shaft. There is. For example, it has been pointed out that if the above-mentioned steel types such as SCM440 and SNCM439 are used as the crankshaft of a 5000-ton press forging machine, it will break within one year of operation.

The present invention solves the above-mentioned problems and provides an SCM4
Crankshaft of a press forging machine, which has a shock resistance superior to that of 40 and SNCM439, and can significantly extend the service life of the crankshaft when used as a material for the crankshaft of a press forging machine. The purpose is to provide steel materials for use.

[0006]

To achieve the above object, in the present invention, C: 0.22 to 0.32% by weight, Si: 0.15% by weight or less, Mn: 0.60% by weight. % Or less, P: 0.020% by weight or less, S: 0.020% by weight or less, Ni: 3.25 to 4.20% by weight, Cr: 1.25 to 2.0
Provided is a steel material for a crankshaft of a press forging machine, which is characterized by 0% by weight, Mo: 0.20 to 0.60% by weight, V: 0.17% by weight or less, and the balance being substantially Fe. .

In the steel material of the present invention, C is a component necessary to secure the quenching hardness on the surface of the steel material at the time of quenching treatment and improve wear resistance and fatigue resistance, and therefore C is 0.22. It is contained by weight% or more. But,
If the content is too large, the toughness and machinability will be deteriorated, so the content is set to 0.32% by weight or less. Si is a component that acts as a deoxidizing agent during melting, and at the same time contributes to the improvement of toughness. However, if the content is too large, an abnormal layer will be formed on the surface during quenching. The amount is limited to 0.15% by weight or less.

[0008] Mn is a component that is effective as a deoxidizing agent during melting and at the same time contributes to the improvement of hardenability and strength, but if it is contained in too much, it causes a decrease in toughness, so its content is 0. Limit to less than .60% by weight. P, S
Is a component that is included as an impurity,
For example, when the content of P is large, the strength is remarkably reduced, and when the content of S is large, inclusions are generated in the steel material, which is a starting point and easily breaks. All the contents are limited to 0.020% by weight or less.

Ni is a component that contributes to the improvement of hardenability and toughness, and for that purpose, it is contained in an amount of 3.25% by weight or more.
However, if the content is too large, the above-mentioned effect only reaches saturation and not only the cost is increased, but also the machinability is deteriorated, so the content is 4.20% by weight.
Limited to: Cr is a component that improves corrosion resistance and enables deep quenching. For that purpose, 1.25 wt% or more is contained. However, if contained too much, the machinability will be deteriorated, so the content is
Limit to 2.00% by weight or less.

Mo improves not only hardenability but also
It is an effective component for increasing the tempering resistance by forming double carbide together with Cr, and for that purpose, 0.2
It is contained in an amount of 0% by weight or more. However, if the content is too large, the above-mentioned effects reach saturation and the machinability and toughness decrease, so the content is limited to not more than 0.60% by weight.

V is a component necessary for enhancing the toughness and especially for improving the impact resistance, but if it is contained in too much, it causes deterioration of the hardenability, so its content is 0.
It should be 17% by weight or less. The steel material of the present invention is obtained by forging and annealing a predetermined amount of each component described above, for example, by vacuum refining, forging and annealing, and then cutting into a predetermined shape as a crankshaft, normalizing, quenching, It can be manufactured by sequentially performing tempering.

[0012]

Examples of the invention

Examples 1 to 3 Steels having the compositions shown in Table 1 were melted and 1800 under the following conditions.
The crankshaft of a press forging machine for tons was manufactured.
That is, molten steel is ingoted, forged, furnace-cooled at 830 ° C, annealed, and then rough-worked at 850 ° C.
Oil cooling and air cooling at 580 ° C. were sequentially performed for quenching, tempering, and finally finishing processing into a predetermined shape.

The mechanical properties of each steel material were measured, and the values are shown in Table 1. In addition, the press forging machine is pressed with a pressure of 1800.
It was operated for 8 hours a day for 8 tons, and the life until the crankshaft was broken was measured. The results are also shown in Table 1.

[0014]

[Table 1]

[0015]

As is clear from the results shown in Table 1, the steel material of the present invention is superior in mechanical properties to the conventional SNCM439 material used as the crankshaft material of the press forging machine. There is. Above all, the shock resistance is remarkably excellent. As a result, the life of the crankshaft is extended to about four times or more, and its industrial value is extremely large.

Claims (1)

Claims: C: 0.22 to 0.32% by weight, Si: 0.1
5% by weight or less, Mn: 0.60% by weight or less, P: 0.020
% By weight, S: 0.020% by weight or less, Ni: 3.25 ~
4.20% by weight, Cr: 1.25 to 2.00% by weight, Mo: 0.0.
A steel material for a crankshaft of a press forging machine, characterized in that the content is 20 to 0.60% by weight, V: 0.17% by weight or less, and the balance is substantially Fe.