JPH05125483A - Steel for machine structural use having good chip disposability and cutting tool life and lower anisotropy of mechanical properties - Google Patents

Abstract

PURPOSE:To improve chip disposability and cutting tool life and to lower the anisotropy of mechanical properties by specifying C, Si, Mn, P, S, and Al, simultaneously adding In and Te to the steel and adjusting the ratios thereof. CONSTITUTION:This steel for machine structural use is constituted by incorporating 0.001 to 0.05% In and 0.004 to 0.2% Te into a steel for structural purposes and satisfying the conditions of [Te]/[In]; <4 and ([Te]-0.9[In])/[S];>=0.14 (where []denote weight % of the respective elements). The In in the steel is made to exist in the form of the metal phase of the In alone and the intermetallic compd. of the In and Te. The above-mentioned steel for structural purposes contains 0.03 to 0.6% C, <=0.5% Si, 0.3 to 2% Mn, <=0.12%P,<0.2% Si, and 0.01 to 0.1% Al. The above-mentioned steel has the good chip disposability and cutting tool life, the improved ductility and toughness in a transverse direction and the smaller anisotropy of the mechanical properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel for machine structural use, which has good chip disposability and cutting tool life, and has little anisotropy in mechanical properties.

[0002]

BACKGROUND OF THE INVENTION Anisotropy of mechanical properties in mechanical structural steel, that is, anisotropy when measured in a rolling direction and a transverse direction at right angles to the rolling direction can be reduced by decreasing the S content. There is a problem that the machinability represented by tool life and chip disposability is greatly reduced. Some S
The addition of Te to the steel containing not only improves the cutting tool life, but also makes the MnS inclusions spherical, thereby improving the ductility and toughness in the transverse direction and increasing the anisotropic mechanical properties. It is known that there is an advantage of reducing the sex. However, there is a drawback that the addition of Te does not improve the chip disposability. The chips need to be removed because they may interfere with the cutting process or damage the work material or the tool, and the productivity of the cutting process is affected by the ease of removing the chips. In particular, in advancing unmanned cutting, the difficulty of removing chips is likely to become a bottleneck, and there is a growing demand for improvement in chip disposability. On the other hand, addition of Pb and Bi is known to improve chip disposability, but both have poor yields during melting, making it difficult to control the components.
Has the problem of being toxic. Therefore, it is required to develop a steel for machine structural use which can improve both chip disposability and tool life without causing problems such as Pb and Bi addition, and has little anisotropy in mechanical properties. ..

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and provides a steel for machine structural use, which has both good chip disposability and tool life, and a small anisotropy of mechanical properties. It is intended.

[0004]

According to the present invention which has achieved the above object, C: 0.03 to 0.6%, Si: 0.5% or less, Mn: 0.3 to 2%, P: 0.12% or less, S: 0.2 % Or less, Al: 0.01 to 0.1% in machine structural steel,
In: 0.001 to 0.05%, Te: 0.004 to 0.2%,
And both conditions of [Te] / [In] <4 and ([Te] -0.9 [In]) / [S]> 0.14 (where [] indicates the weight% of each element present in the steel) In the steel, In is present as both a metallic phase of In alone and an intermetallic compound of In and Te, and the balance is Fe and inevitable impurities.

[0005]

In order to improve the chip disposability, it is effective to reduce the breaking strain of the chips. On the other hand, since the temperature of chips increases due to high-speed plastic deformation during cutting, molten metal embrittlement (embrittlement due to partial melting of metal) does not deteriorate the mechanical properties at room temperature and allows chip disposability. Can improve. The addition of Pb and Bi described in the section of the prior art utilizes the fact that they cause brittle metal embrittlement and improve the chip disposability, but there are many problems as described above.
On the other hand, In has the advantages that a small amount of In improves the chip disposability, has a good yield, facilitates component control, and has no toxicity. However, In alone does not improve the tool life, and does not have the function of making the MnS inclusions spherical and reducing the anisotropy of mechanical properties.

However, according to various studies conducted by the present inventors, it has been found that the tool life can be improved by forming an intermetallic compound of In and Te such as InTe and In ₂ Te _3. Was given. That is, the present invention
By making the composite addition of Te and Te and adjusting their components, both the intermetallic compound of In and Te and the In independent phase are present, thereby satisfying both chip disposability and tool life. Is a successful one. Further, not only the combined addition of In and Te, but also the further adjustment of the components, succeeded in reducing the anisotropy of mechanical properties while further improving the chip disposability and tool life. Came to. Next, the reasons for limiting each element will be described.

C: 0.03 to 0.6% C is an essential element for ensuring the necessary strength, and if it is insufficient, machinability deteriorates, so the lower limit was made 0.03%. However, if C is contained in an unnecessarily large amount, the machinability and toughness decrease, so the upper limit was made 0.6%. Si: 0.5% or less Si may be used as a deoxidizing aid, but if it is contained in excess, machinability and toughness decrease, so the upper limit is set to 0.
It was set to 5%. Mn: 0.03 to 2% Mn is required to be at least 0.03% in order to form MnS that is effective in improving machinability and hot workability, but if added in excess, machinability is reduced, so the upper limit is made 2%. did.

P: 0.12% or less P may be added to improve the machinability, but if it is contained excessively, the toughness deteriorates, so the upper limit is 0.12%.
And S: 0.2% or less S may be added to form MnS to improve machinability, but if added in excess, it deteriorates hot workability and reduces ductility and toughness in the width direction. Since this increases the anisotropy, the upper limit was made 0.2%. Al: 0.01 to 0.1% Al is added as a deoxidizing agent for steel materials, and 0.01% or more is required. If the deoxidation is insufficient, a large amount of oxide-based inclusions are present in the steel, which reduces both fatigue strength and toughness. However, if added too much, the machinability will decrease.
It was set to 0.1%.

In: 0.001 to 0.05% As described above, In is contained for the purpose of improving chip disposability and tool life. However, if it is less than 0.001%, its effect is poor, and even if it is contained in an appropriate amount or more, no noticeable increase in effect is observed and the cost is rather increased. Therefore, the upper limit was made 0.05%. Te: 0.004 to 0.2% Te forms intermetallic compounds with In, improves the tool life by its lubricating action, and forms a solid solution in MnS inclusions to form MnS inclusions into spheroids, resulting in ductility and toughness. It is contained for the purpose of reducing the anisotropy of mechanical properties such as. However, if it is less than 0.004%, its effect is poor, and even if it is contained in an appropriate amount or more, no noticeable increase in effect is observed, and the upper limit is 0.2 because the cost is rather high.
%.

In order to improve chip disposability, In
Must be contained in a sufficient amount. But T
If the ratio of e / In is too large, most of In is fixed as an intermetallic compound with Te, and the chip disposability is not improved. Therefore, [Te] / [In] <4 (where [] indicates the weight% of each element present in the steel)
It is necessary to satisfy the conditions of. On the contrary, if the amount of Te is too small, the amount required to make MnS spheroidize cannot be dissolved in MnS inclusions. In order to form a solid solution of Te in the MnS inclusions, a sufficient amount of Te for spheroidizing MnS must satisfy the condition of ([Te] −0.90 [In]) / [S]> 0.14. (However, [] indicates the weight% of each element present in the steel)

In addition to the above-mentioned elements, the steel of the present invention contains Ni, which improves the hardenability of the steel and the strength and toughness after tempering.
At least one element selected from the group consisting of Cr and Mo may be contained. However, even if these elements are added excessively, no remarkable increase in the effect is recognized, which further increases the manufacturing cost, and the upper limit of the addition amount is Ni: 5
%, Cr: 2% and Mo: 1.5%.

In order to further improve machinability, Pb,
At least one element selected from the group consisting of Bi and Ca may be contained. The minimum amount required to improve machinability is 0.01% for Pb and Bi and 0.0005% for Ca. However, even if these elements are added excessively, no remarkable increase in the effect is observed, which further increases the manufacturing cost. The upper limit of the addition amount is 0.4% of Pb and Bi and 0.4% of Ca.
0.01%.

[0013]

EXAMPLES The effects of the method of the present invention will be described based on examples. Table 1 shows the chemical composition of the test material. For the machinability test, after normalizing, using a cemented carbide tool P20 on a CNC lathe, speed 300 / min, feed 0.25 mm / re
v, turning was performed in the longitudinal direction with a notch of 0.5 mm, and the flank wear amount and chip disposability were observed. Tool life was compared by cutting time until a predetermined wear amount was reached. The chip disposability was indexed and compared so that the shorter the chips, the higher. Table 2 shows the results of the machinability test and the ratios of the ductility and Charpy impact values measured after tempering between the transverse direction and the rolling direction.

[0014]

[Table 1]

[0015]

[Table 2]

It was observed that the steel of the present invention has good chip disposability and tool life, has improved toughness in the transverse direction, and has reduced anisotropy of mechanical properties. On the contrary, steels that deviate from the conditions of the present invention are observed to be inferior in some properties. For example, sample No.13, and
No.15 has poor chip control, and sample No.14 has a short tool life. In addition, samples No.14 and No.16 to No.18
In comparison with the steel of the present invention containing the same amount of S, it is observed that the anisotropy of mechanical properties is large.

[0017]

As described above, according to the present invention, by simultaneously adding In and Te and adjusting the amounts thereof, the chip disposability and the cutting tool life are improved, and the ductility in the lateral direction is improved. It has become possible to improve the toughness and to reduce the anisotropy of mechanical properties.

Claims (3)

[Claims] 1. C: 0.03 to 0.6% (meaning weight%; the same applies hereinafter), Si: 0.5% or less, Mn: 0.3 to 2%, P: 0.1
In mechanical structural steel containing 2% or less, S: 0.2% or less, and Al: 0.01 to 0.1%, In: 0.001 to 0.05%, Te:
0.004 to 0.2%, and [Te] / [In] <4 and ([Te] -0.9 [In]) / [S]> 0.14 (where [] is the weight% of each element present in the steel. And In exists in the steel as both a metallic phase of In alone and an intermetallic compound of In and Te, the balance being Fe and unavoidable impurities. Mechanical structural steel with good scrap handling and cutting tool life, and little anisotropy in mechanical properties. 2. Further, it contains one or more of Ni: 5% or less, Cr: 2% or less, Mo: 1.5% or less, good chip disposability and cutting tool life, and good mechanical properties. The steel for machine structural use according to claim 1, which has little anisotropy. 3. Bi: 0.01-0.4%, Pb: 0.01
~ 0.4%, Ca: 0.0005 ~ 0.01%, 1 or 2
The steel for machine structural use according to claim 1 or 2, which contains at least one kind and has good chip disposability and cutting tool life, and little anisotropy in mechanical properties.