DE4333017A1 - Solid shaft for use as drive shaft - Google Patents

Abstract

There is described a compact and high-performance or high-strength, solid shaft for use as a drive shaft, which has a relatively high torsional strength and which can easily be machined and which is free of contaminant concentrations at the serrated parts. The solid shaft which has serrated parts is made from an alloy composition comprising the following: C: from 0.38 to 0.45 % by weight, Si: 0.35 % by weight or less, Mn: from 0.8 to 1.5 % by weight, B: from 0.0005 to 0.0035 % by weight, Ti: from 0.1 to 0.05 % by weight and Al: from 0.01 to 0.06 % by weight, where the content of N is not greater than 0.01 % by weight and the remainder is essentially Fe. The shaft has a surface hardened by means of induction hardening and a hardening parameter HRC of 55 or greater. The ratio of the hardened depth to the radius of the shaft is not less than 0.45.

Description

The invention is concerned with a massive shaft for ver application as a drive shaft in a vehicle, and esp especially with a massive shaft for use as an on drive shaft in connection with constant velocity joints.

In general, the torque generated in an internal combustion engine is transmitted to a solid shaft via a transmission, a differential and a homokinetic joint, and then to a hub and a wheel via another homokinetic joint. As shown in FIG. 1, such a massive shaft 1 in the drive system has serrated parts 3 at both ends for connection to the homokinetic joints 2 . The torque of the internal combustion engine is applied to the splined parts.

A massive shaft is for use as a drive shaft required to have sufficient torsional strength over the to have entire length. Furthermore, the splined Parts machined to high accuracy to provide a necessary distance, etc. and Bela to avoid concentration concentrations.

Common solid shafts of this type are made of one coal medium-grade steel, such as A ISI 1541 or S40C which is steel for rolling or rolled steel acts. The steel material is first heat treated to the improve machinability, then it becomes a required shape by means of rolling and machining awarded and finally there is an induction hardening to Hardening the surface to a required torsional strength to achieve.  

A massive shaft for use as a drive shaft, which by machining and induction hardening an ordinary medium grade carbon steel such as S40C is prone to chilling tears. It is also through hardening formed hardened layer so thin that the torsional strength expressed in the size of the maximum shear stress (τmax) at break was not greater than 1.27 GPa (130 kgf / mm²). Therefore, it was difficult to meet the requirements for smaller ones lighter drive systems in terms of weight.

In particular, the dimensions of the solid shaft are sufficient accordingly, it must have a torsional strength of at least 1.47 GPa (150 kgf / mm²) based on the maximum Have shear stress (τmax). Has none of the usual waves such a high torsional strength.

The invention aims to be compact and tall solid solid shaft for use as a drive shaft to sit, which has a higher torsional strength at a has the required maximum shear stress, which maschi nell can be edited with high accuracy and that freely of stress concentrations on the serrated parts.

According to the invention there is provided a solid shaft for use as a drive shaft, the solid shaft having serrated parts and made from an alloy composition which is 0.38 to 0.45 wt% carbon, 0.35 wt% % or less silicon, 0.8-1.5% by weight magnesium, 0.0005-0.0035% by weight boron, 0.01 to 0.05% by weight titanium and 0.01-0, 06 wt .-% aluminum, wherein the nitrogen content is not greater than 0.01 wt .-% and the rest essentially comprises iron and unavoidable impurities. The solid shaft has a surface which is hardened by induction hardening and has a hardness H _R C of 55 or greater, the ratio of the depth of hardening to the radius of the solid shaft being not less than 0.45.

Alloy components for the massive shaft after Invention, the carbon content (C) should be 0.38 to 0.45% by weight (hereinafter simply expressed as "%") fen. If this is less than 0.38%, the massive wave would have insufficient torsional strength and impact resistance. If it is greater than 0.45%, the machinability and the rollability extremely unfavorable. Then it can easily occur that the waves produced from this deterrent has cracks.

The silicon (Si) content should be 0.35% or less. Although it requires a small amount of silicon as one Add deoxidizers to increase processability and The productivity of the steel material would increase the cold rollability become very unfavorable if the content is greater than Is 0.35%.

The manganese (Mn) content should be 0.8 to 1.5%. Magne sium in such an area improves the hardenability by means of Induction. A magnesium sulfide compound is also formed and thereby the machining is cheaper. If we less than 0.8% are contained, can not be sufficient Achieve improvement in hardenability. If the salary is greater than 1.5%, the cold rollability is adversely affected.

The boron (B) content should be 0.0005-0.0035%. A such amount of boron is used to improve hardenability Strengthening the grain boundaries and increasing the impact strength. If it is less than 0.0005%, you get this preferred property is not sufficient. If he is greater than 0.0035%, not only will not hardenability in sufficiently improved, but the excretion of Fe₂B during the rolling leads to cold cracks.

The levels of titanium (Ti) and aluminum (Al) should each Make up 0.01-0.05% and 0.01-0.06%. They both serve to Fix nitrogen and oxygen in the material. If at  for example, the material dissolved in a solid state Containing nitrogen, nitrogen tends to pick up boron take and form a boron nitride compound, which prevents It is changed that boron can improve the hardenability. If the Alloy contains Ti and Al, but are preferably TiN and AlN formed. This enables boron to have its effect can develop to improve hardenability. To this end the content of each element should be 0.01% or more do. On the other hand, an excessive addition of Ti and Al does not is only inappropriate, but also the purity of the alloy composition should affect the upper limit values for Ti and Al are 0.05% and 0.06% respectively.

The nitrogen (N) content should be 0.01% or less. If it is larger than 0.01%, boron nitride is formed, whereby the amount of free boron atoms decreases, which the to improve hardenability.

To further enhance the machinability of the alloy To improve composition according to the invention, elements such as S, Pb, Te or Ca, can be added to the composition. Around Cr and / or Mo can also improve the hardenability are given. In this case, the Cr and / or Mo Content does not exceed 0.05% and 0.2%, respectively, so that machine machinability is not degraded. By the addition of 0.1% or less of Nb can also be made Impact resistance and sensitivity to quenching make cracks cheaper.

The solid shaft made of the alloy composition described above should be subjected to induction hardening to form a hardened layer having an H _R C (Rockwell C hardness) of 55 or more so that the ratio of Depth to shaft radius becomes 0.45 or greater. If the ratio is less than 0.45, the torsional strength of the solid shaft is insufficient and the maximum shear stress (τmax) becomes less than 1.47 GPa (150 kgf / mm²). The hardened depth is the distance from the surface at which the Vickers hardness HV is measured according to the method according to JIS G0559, which is higher than 392 (equal to H _R C 4).

The massive shaft for use as a drive shaft after the Invention is made from an alloy composition which has a higher martensite transformation temperature than usual Has materials, and contains a predetermined amount of boron (B). Because such a composition has a fine grain structure (Ferrite grain size number is 6 or larger) is the Low sensitivity to bevel cracks. The hardened Layer formed by induction hardening in such a way that they have a predetermined surface hardness and a predetermined one Depth has the torsional strength of the massive shaft increase so that the maximum shear stress on little at least 1.47 GPa (150 gkf / mm²) increases.

Furthermore, since the splined parts are formed at a precise distance load concentrations can be detected avoid. The dimensions of the shaft can also be as small as possible make small and you still get the high-strength load properties.

Further details, features and advantages of the invention are shown ben from the following description of preferred Aus management forms with reference to the accompanying drawing. It shows:

Fig. 1 is a front view of a preferred embodiment;

Fig. 2 is a diagram showing the relation between the maximum shear stress and the ratio of the hardened depth to the shaft radius and surface hardness; and

Fig. 3 is a diagram to illustrate the fatigue strength of the massive waves with completely reverse torsion.

(EXAMPLES 1-21)

As material for the massive shafts 1 , which are shown in FIG. 1 and which are designated there with 87AC and 109AC (which are the dimensions of the homokinetic joints used), an alloy composition was prepared, which C with 0, 38-0.45% by weight, Si with 0.35% by weight or less, Mn with 0.8-1.5% by weight, B with 0.0005 to 0.0035% by weight, Ti with 0.01 to 0.05 wt .-% and Al with 0.01 to 0.06 wt .-%, wherein the content of N is not greater than 0.01 wt .-% and the rest is essentially Fe . This alloy composition is formed into the material for the shafts 1 by rolling at a lower temperature with a heating temperature of 1100 ° C or less and a finishing temperature of 950 ° C or less so that the cross-sectional reduction is 70% or more . The dimension data of the shafts are shown in Table 1.

As shown in Fig. 1, the solid shaft 1 has serrated parts 3 , circumferential recesses 5 , which are provided at both ends for receiving snap rings 4 , and circumferential measures 7 , the central parts of which are designed to accommodate sleeves 6 .

The solid shafts 1 thus formed are processed by induction hardening under the following conditions, so that the ratio (γ) of the hardened depth to the shaft radius and the surface hardness (H _R C) have values which are shown in Table 2.

(Conditions of induction hardening)

Frequency: 8 kHz
Power: 250 KW
Transport speed: 5.7-9.3 mm / sec

The massive waves obtained were subjected to a torsion test in order to measure the maximum shear stress τmax). The results are shown in Table 2. The relationships between the maximum values shown in Table 2 and the ratios of hardened depth to shaft radius are plotted in Fig. 2 using the symbols shown in Table 2 (different symbols were used for different surface hardnesses).

(Comparative Example 7)

Solid shafts were made in exactly the same way as the EXAMPLES, except that they were made from a common S40C material (C: 0.37-0.43 wt%, Si: 0.15-0.35 wt. %, Mn: 0.60-0.90% by weight, P: 0.30% by weight or less, and S: 0.035% by weight or less). The waves obtained were measured with regard to the ratio γ of the hardened depth to the radius of the wave and the maximum shear stress. The results are entered in FIG. 1 using the symbol X.

As can be seen from the results according to Table 2 and Fig. 2 compared to Comparative Examples 1 to 7, the ratios are less than 0.45 and the maximum shear stress (torsional strength) was less than 1.47 GPa. In contrast, in EXAMPLES 1 to 21 (with H _R C of 55 or greater), the ratios were γ 0.45 or greater, which means that the cured depths were sufficiently large. Furthermore, the maximum shear stress was greater than 1.47 GPa in each EXAMPLE. These shafts had a high torsional strength, so that their dimensions could be reduced to a sufficient extent.

(EXAMPLES 22-24)

A total of 12 solid shafts were produced as in EXAMPLE 22 with ⬩ (shaft diameter D = 28.1 mm, surface hardness H _R C ≧ 55, γ = 0.55); EXAMPLE 23 marked with Δ (shaft diameter D = 22.2 mm, surface hardness H _R C 55, γ = 0.64) and EXAMPLE 24 marked with ⚫ (shaft diameter D = 28.1 mm, surface hardness H _R C ≧ 55, γ = 0.75): The massive shafts of the respective EXAMPLES were subjected to a fatigue test with completely reverse torsion. The test results are shown in FIG. 3. The shafts marked according to Comparative Example 6 mi X (shaft diameter D = 28.1 mm, γ = 0.33) were subjected to the same fatigue test. The results are also shown in Fig. 3.

In particular, the Y-axis represents the maximum shear stresses τmax a mean of the acting torque and the shaft diameter with broken parts, while the X-axis represents the number of cycles N (generally given in logarithmic sizes) for the torsional stress until the shafts break. The ratio of hardened depth to shaft radius at the broken part is shown as a parameter γ. The straight lines shown in Fig. 3 are derived lines obtained from test results.

As can be seen from the results according to FIG. 3, the fatigue strength is greater in proportion to the ratio γ when the torsion stress is completely reversed. The fatigue strengths of the shafts in EXAMPLE 23 (Δ, γ = 0.64) and EXAMPLE 24 (⚫, γ = 0.75) have essentially the same values. It can be seen that saturation occurs at about γ = 0.65 with regard to the torsion test. When comparing with Comparative Example 6 (X, γ = 0.33), which has a torsional strength of 1.27 GPa (130 kgf / mm²), EXAMPLES 22 through 24 have significantly improved torsional strength values.

None of the EXAMPLES given above occurred Quench cracks on the serrated parts. With regard the machinability considering the work The cutting performance was the test machine for mass production as big as the comparative examples while the others  machinable properties including the Centering, machining the outer diameter, of rolling, serration and to form the recess Measures for the snap ring cheaper than the comparison are examples. In EXAMPLES 1-24, the Distance deviations x to 0.03 on average, which is half as large or less than half of the distance deviations x of 0.06 at Comparative Examples 1 to 7. This means that the on the teeth of the serrated parts act equally are moderate.  

table

Table 2

Claims (1)

Solid shaft for use as a drive shaft, the solid shaft having serrated parts and made of an alloy which is characterized in that it contains 0.38 to 0.45% by weight of carbon, 0.35% by weight or less silicon, 0.8 to 1.5 wt% manganese, 0.0005 to 0.0035 wt% boron, 0.01 to 0.05 wt% titanium and 0.01 to 0.06 Has wt .-% aluminum, the nitrogen content is not greater than 0.01 wt .-% and the rest is essentially iron and unavoidable impurities, that the solid shaft has a surface hardened by means of induction hardening, and a hardness H _R C is 55 or greater, and the ratio of the hardened depth to the radius of the solid shaft is not less than 0.45.