JP3218209B2 - High strength bolt friction welding steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary steel material used for a high-strength bolt friction joint.

[0002]

2. Description of the Related Art In many conventional frictional joints using high-strength bolts, it is standard to use an attachment plate having a red rust surface or a shot blast surface, but the slip coefficient obtained by this is at most 0. It is about 45. FIG. 1 is a schematic view of an attachment plate used for a steel bolt joint shown in FIG. 15 of JP-A-8-209809. In addition,
1A is a side view, and FIG. 1B is a plan view.

[0003] Here, several techniques aimed at increasing the slip coefficient have been disclosed.
In JP-A-09809, when a triangular corrugated or pyramid-shaped projection is provided on the friction surface of the contact plate and the ratio of the hardness of the contact plate to the hardness of the other steel material is 2.5 or more, the slip coefficient is 0.9.
It was clarified that the above-mentioned high friction joining surface could be obtained. Japanese Patent Application Laid-Open No. 8-81736 discloses that a high hardness steel material in which the addition amounts of Ti and B are limited has a height difference of 0.2 to 1.0 mm.
A high friction steel material with irregularities is presented. These steel materials basically have irregularities on the surface of the steel material, and these projections bite into the aggregate to obtain friction. Therefore, it can be said that this is an excellent technique for obtaining high friction.

However, the above-mentioned steel materials do not take into account any technical considerations in the recesses, that is, the notch effect when the tensile stress applied during use of the attachment plate is concentrated at the tip of the valley bottom of the recesses. During use, a crack may be generated from the tip, and the attachment plate may be broken by low stress.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been successful in reducing the concentration of stress at the bottom of a concave valley and providing a high frictional joint surface. The present invention relates to a steel material for contacting a force bolt friction joint structure.

[0006]

The main feature of the steel material for joining a high-strength bolted friction joint structure according to the present invention is that a steel material basically having excellent hardenability and toughness is used and its surface, that is, at least an aggregate (coated) is used. The protrusion height is 0.25 on the friction surface with the
In addition to obtaining a high friction surface with extremely strong bite into the aggregate by having triangular protrusions of up to 2 mm, an interval between adjacent protrusions of 0.5 to 4 mm, and a protrusion tip radius of 0.1 mm or less, The important point is that, as shown in FIG. 2, the bottom of the concave portion between the adjacent protrusions is rounded, and the stress concentration there has been significantly reduced. As the roundness at this time, an arc, an ellipse, or the like is appropriate.
An arc of 05 mm or more is easy to machine and suitable for reducing stress concentration.

The gist of the present invention is as follows.

(1) The chemical composition is, by weight, C: 0.1-1%, Si: 0.05-1%, Mn: 0.3-1.5%, and the balance is Fe and inevitable. Steel having at least one surface with a height of 0.25
２2 mm, the interval between adjacent protrusions is in the range of 0.5 突起 4 mm, and the valley bottom radius of curvature is 0.05〜8.
A high-strength bolt friction joining steel material having a stress concentration-relieving shape of 125 mm and a Vickers hardness of 400 to 700 at a protrusion.

[0009]

( 2 ) The steel composition described in (1) further contains one or two of P: 0.015 to 0.05%, and S: 0.015 to 0.05%. Characterized by
(1) The high-strength bolt friction joining steel material according to (1) .

( 3 ) In addition to the steel composition described in (1) or (2) , Ni: 0.1-1%, Cr: 0.1-2%, Mo: 0.1-1%, V: Characterized in that 0.01 to 0.1% of one or more kinds are contained.
The high-strength bolt friction joining steel material according to (1) or (2) .

( 4 ) (1) or (2), or
( 1) or (2), wherein the steel composition according to (3) further contains Nb: 0.01 to 0.5% .
Or the high-strength bolt friction joining steel material according to (3) .

( 5 ) (1) or (2) or
The steel composition according to (3) or (4) , further comprising one or two of Al: 0.01 to 0.1% and Ti: 0.005 to 0.1%. To be
(1) or (2) or (3) or (4)
High-strength bolt friction welding steel. (6) (1) or (2) or (3) or
(4) or (5), wherein B: 0.0003-0.005% is further contained in the steel composition described in (1) or (2).
Or (3) or (4) or (5).
Steel for friction welding.

(7) (1) or (2) or (3)
Or (4) or (5) or (6), further containing one or two of Ca: 0.001 to 0.01% and REM: 0.01 to 0.05% (1) or (2) or (3) or (4) or (5), or (6), wherein the high-strength bolt friction-joining steel material is used.

[0015]

Next, the reasons for limiting each component of the present invention will be described. In addition, all% are weight%.

The steel composition is basically rich in hardenability, so that the hardness of the tip of a projection (for example, a triangular or triangular pyramid) can be easily secured, and the growth of a crack caused by stress concentration at the bottom of the projection valley is easily prevented. The steel toughness must also be excellent to control.

Control of C is extremely important for the present invention. In order to obtain hardness at the tip of the projection, at least 0.1% or more is necessary. If it exceeds 1%, cracks may easily occur from the bottom of the valley even if the projection has a stress concentration relief shape at the bottom of the valley. is there. Thus the addition range of C is 0.1 to 1%.

Si needs to be at least 0.05% from the viewpoint of deoxidation and securing the hardness, but if it exceeds 1%, cracks are liable to be generated from the valley bottom even if the projection has a valley bottom stress concentration relieving shape. May be. Therefore, the addition range of Si is 0.05
To 1%.

Mn fixes S and prevents grain boundary cracking during hot working, and at least 0.3% from the viewpoint of securing hardness.
However, if it exceeds 1.5%, cracks may be easily generated from the bottom of the valley even if it has a shape for relieving stress concentration at the bottom of the projection valley. Therefore, the addition range of Mn is 0.3 to
1.5%.

P and S are grain boundary embrittlement elements and must be restricted in toughness, but have the effect of improving the free-cutting properties of steel materials. 0.015 for both P and S from the viewpoint of improving the free-cutting property
% Or more is desirable, but if it exceeds 0.05%, the basic toughness of the steel material is reduced. Therefore, when adding P and S, the range is made 0.015 to 0.05%.

Ni, Cr, Mo, and V can all be added from the viewpoint of improving the hardness of the projections.

Ni is added in an amount of at least 0.1% when added because of its effect of securing desired hardness and improving basic toughness of steel.
However, the addition of more than 1% is not preferable because the quenching property is excessive, and even if the stress relaxation shape of the present invention is provided, cracks are easily generated in the projection valley stress concentration portion. Therefore, the range of addition of Ni is 0.1 to 1%.

From the viewpoint of securing a desired hardness, Cr needs to be added in an amount of at least 0.1% when added. However, when added over 2%, it has an excessive hardenability, and therefore has the stress relaxation shape of the present invention. However, cracks are likely to occur in the projection valley stress concentration portion. Therefore, the range of addition of Ni is 0.1 to 2
%.

Mo and V are also desirable elements for securing a desired hardness like Cr, and when they are added, they need at least 0.1% and 0.01%, respectively, but 1% each.
If the addition exceeds 0.1%, the quenching property is excessive, so that even in the case of having the stress relaxation shape of the present invention, cracks are likely to occur in the stress concentration portions of the projection valleys. Therefore, when Mo and V are added, the range of addition of Mo is 0.1 to 1% and V is 0.01%.
To 0.1%.

Nb has an effect of improving the base material toughness of the steel material through the effect of grain refinement.
Although 1% is required, addition of more than 0.5% results in the formation of coarse precipitates such as NbC, which in turn causes a decrease in toughness.
Therefore, the addition range of Nb is set to 0.01 to 0.5%.

Al and Ti are preferably added as deoxidizers, and Al and Ti also have a function of suppressing the formation of BN by forming a compound with N. As a result, the concentration of solid solution B increases, which segregates at austenite grain boundaries, thereby improving the hardenability, and as a result, the hardness increases. To achieve this effect, the content of Al is set to 0.1.
Addition of not less than 01% and not less than 0.005% of Ti is required. However, addition of more than 0.1% both forms a coarse nitride and lowers the base metal toughness of the steel material. Therefore, the addition range of Al is 0.01 to 0.1%, and the addition range of Ti is 0.005%.
~ 0.1% is preferred. In addition, Al may be mixed as an impurity from alloys or refractories at the time of smelting steel.
% Can be regarded as inevitable impurities.

B causes an increase in hardness through hardenability as described above. For this purpose Al and / or T
Addition of i and further addition of at least 0.0003% is required. However, addition of more than 0.005% leads to formation of coarse precipitates of BN and lowers toughness. Therefore, the addition range of B is 0.0003 to 0.005%.

Ca and REM have the function of improving the anisotropy of the steel material by controlling the refinement of inclusions and improving the toughness of the base material. However, excessive addition of Ca and REM causes the inclusions to become coarser and lowers the toughness. The range of addition is as follows.
001-0.01%, REM is 0.01-0.05%.

Here, factors governing the friction surface characteristics of the steel sheet will be described. Triangular projections as shown in FIG. 2 are most preferable as shapes that cut into building aggregates and bring about friction,
It is desirable that the tip 1 of the projection be sharp with an angle of 90 °. The projections may be other than triangular, triangular pyramid or quadrangular pyramid. If the protrusion height t is less than 0.25 mm, sufficient bite cannot be obtained, and if it exceeds 2 mm, the total w And the slip coefficient cannot be obtained. Therefore, the range of the height t of the projection is 0.25 to 2 mm. Furthermore, it is better that the interval between adjacent protrusions is small, and this value should not exceed 4 mm.
On the other hand, if it is less than 0.5 mm, the height of the projections becomes small, so that bite cannot be obtained. Therefore, the range of the adjacent projection distance w is 0.5 to 4 mm. As for the hardness of the projection, the shaded portion shown in FIG. 3 (preferably, but not limited to 0.4 × t or less) is the most important for biting, and the Vickers hardness of this portion is important. 400 or more is necessary, but if it exceeds 700, cracks tend to occur in the protruding valley bottom 2. Therefore, the range of the protrusion hardness is 400 to 700.
It is.

Further, if the shape of the protrusion valley bottom 2 which is important in the present invention is sharp (for example, notch-like), stress concentration is generated due to tensile stress during the use of the joining steel material, and as a result, There is a possibility that the joint steel material may be broken. Therefore, the bottom of the valley needs to have a rounded cross-sectional shape (ellipse, circle, etc.). Particularly, as described below, the effect is exhibited when the radius of curvature is 0.05 mm or more. FIG.
(A) shows the relationship between the radius of curvature of the bottom of the projection valley and the maximum tensile stress σmax in the steel composition of the sixth invention of the present invention. FIG.
A stress σ when a tensile load P is applied to an attaching steel material having a shape having a width W and a height A from a valley bottom to a back surface shown in FIG.
Is defined as σ = P / (A × W). The maximum stress .sigma.max in this tension was compared with the tensile strength .sigma.B when a flat plate having a plate width W and a plate thickness A shown in FIG. 4 (c) was pulled. If these were almost equal, it was determined that there was no notch effect at the valley bottom. On the other hand, if σmax <σB, it is considered that the strength decreases due to the concentration of stress in the notch. If the shape of the valley is not sharp and dislocation multiplication occurs at a slight density, the strength increases rather due to work hardening, and although slightly, σmax> σB
A favorable result can be expected. Therefore, FIG.
Then, a tensile test was performed using steel plates having various A and W shapes, and the vertical axis was σmax with respect to the radius of curvature of the horizontal axis.
/ ΣB. If this falls below 1, it can be considered that stress concentration has acted. In particular, the result was much smaller than 1 when the radius of curvature was less than 0.05 mm. On the other hand, the projection height is smaller than the minimum value and larger than the maximum value of the projection interval, and it is difficult to obtain the biting effect. Therefore, the upper limit is particularly 8.125 mm. Therefore, the range of the radius of curvature at the bottom of the projection valley is 0.05 to 8.125 mm.

The high-strength bolt friction joining steel material of the present invention includes a thick plate (for example, a plate thickness of 6 to 25 mm) and a thin plate (for example, a plate thickness of less than 3 to 6 mm) aggregate (substrate to be attached). Any of those obtained by shaping a plate according to the requirements may be used. For example, it may have a substantially U-shaped cross section.

[0032]

EXAMPLE A steel having a composition range shown in Tables 1 and 2 was prepared to a thickness of 9 m.
m of the test steel sheet. No. 1 to 20 are steels of the present invention, N
o. 21 to 47 are comparative steels. Tables 3 and 4 show the protrusion shapes (projection height, adjacent protrusion shape, protrusion valley bottom shape, protrusion valley bottom curvature radius) and protrusion hardness of each test steel sheet. Furthermore, various surface treatments were performed on the surface of each of the manufactured steel sheets, and the slip coefficient μ was measured. For the measurement of the slip coefficient μ, a test sample shown in FIG. 5 is manufactured, and both ends of the test sample are pulled, and the slip is obtained from the relationship between the displacement d and the load P. Especially d = 0.2mm
When the load P _0.2 at the time of is used, it is expressed by μ = P _0.2 / N. Here, N is the introduced axial force of the used bolt, which is nominally 10 T (10 tonf / cm ² ). In the test, a strain gauge was attached to the head of the bolt, and the effective axial force was measured. Further, Tables 3 and 4 show that the strength ratio σmax / σB of the steel plate for attachment and the flat plate measured in the tensile test in order to determine the state of stress relaxation at the bottom of the protrusion, which is the most important point in the present invention.
Is shown.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4] Comparative steel No. Nos. 21 to 29 have the component systems within the scope of the present invention. 21 to 23 and No. 2; 26 has a low slip coefficient because the projection height and the interval between adjacent projections are inappropriate,
No. 24 to 25 are σm since the bottom of the projection valley is notched.
ax / σB is much lower than 1. In addition, No. 2
No. 7 has a low slip coefficient because the radius of curvature of the projection valley bottom exceeds that of the present invention. No. 28 has a low slip coefficient because the protrusion hardness is lower than that of the present invention. In No. 29, the σmax / σB is much lower than 1 because the protrusion hardness is higher than the present invention.

Comparative steel No. 30, 32, and 34 have low slip coefficients, respectively, because C, Si, and Mn are lower than those of the present invention.

Comparative steel No. 31, 33, 35, 36-4
7 are C, Si, Mn, P, S, Ni, and C, respectively.
Since r, Mo, V, Nb, Ti, Al, B, Ca, and REM are higher than those of the present invention, the slip coefficient is sufficient but σmax / σB is much lower than 1.

On the other hand, the steel No. 1 to 20,
The slip coefficient is sufficiently high, and the anti-protrusion valley bottom stress concentration index σmax / σB, which is important in the present invention, is a satisfactory level.

[0040]

According to the present invention, a high-strength bolt friction joining steel material having a high slip coefficient can be obtained. This allows
It is possible to significantly reduce the number of bolts and to apply safe low-strength bolts, and it can be said that the role played by the industry is extremely large from the viewpoint of cost reduction and safety.

[Brief description of the drawings]

FIG. 1 is a view for explaining a conventional attachment plate, in which (a) is a side view and (b) is a plan view.

FIG. 2 is a diagram showing the shape of a steel material projection for attachment.

FIG. 3 is a diagram showing a required range of a protrusion hardness.

FIG. 4A is a diagram showing a radius of curvature of a projection valley bottom and σmax / σB.
FIG. 4B is a diagram showing an example of the relationship of (a), (b) is a diagram showing the appearance of an attached steel tensile test piece, and (c) is a diagram showing the appearance of a comparative flat plate tensile test piece.

FIG. 5 is a view showing a test piece for measuring a slip coefficient.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Protrusion tip part 2 Protrusion valley bottom part 3 Bolt hole 4 Steel material 5 Attached plate (steel material for attachment) t Projection height w Projection interval A Plate thickness W Plate width

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-8-41591 (JP, A) JP-A-6-25803 (JP, A) JP-A-4-73422 (JP, A) JP-A-9-99 4451 (JP, A) JP-A-3-94015 (JP, A) JP-A-4-202629 (JP, A) JP-A-6-128689 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) C22C 38/00-38/60

Claims (7)

(57) [Claims] 1. The chemical composition is, by weight, C: 0.1-1%, Si: 0.05-1%, Mn: 0.3-1.5%, and the balance is Fe and inevitable. At least one surface of a steel material as an impurity has a protrusion, and the protrusion height is 0.25
２2 mm, the interval between adjacent protrusions is in the range of 0.5 突起 4 mm, and the valley bottom radius of curvature is 0.05〜8.
A high-strength bolt friction joining steel material having a stress concentration-relieving shape of 125 mm and a Vickers hardness of 400 to 700 at a protrusion. 2. The steel composition according to claim 1, further comprising one or two of P: 0.015 to 0.05 % and S: 0.015 to 0.05 %. Claim characterized by
Item 4. The steel material for friction joining of high strength bolts according to Item 1. 3. The steel composition according to claim 1 or claim 2.
And further contains one or more of Ni: 0.1 to 1%, Cr : 0.1 to 2%, Mo: 0.1 to 1%, and V: 0.01 to 0.1%. Characterized by
3. A high-strength bolt friction joining attachment according to claim 1 or 2.
For steel. 4. The method according to claim 1, 2 or 3,
The steel composition of the third aspect, further, Nb: claim 1 or claim, characterized in that 0.01-0.5%, and for the additional inclusion of
The high-strength bolt friction joining steel according to claim 2 or claim 3.
Wood. (5) Claim 1 or Claim 2 or Claim
3. The steel composition according to claim 3, further comprising one or two of Al: 0.01 to 0.1% and Ti: 0.005 to 0.1%. Request
Claim 1 or claim 2 or claim 3 or claim 4
High-strength bolts used for friction welding. 6. The method according to claim 1, 2 or 3.
Or the steel composition according to claim 4 or claim 5
And B: 0.0003 to 0.005%.
Claim 2, claim 3, claim 4, or claim 5.
Steel for high-strength bolt friction joining. 7. The method according to claim 1, 2 or 3.
Alternatively, the steel composition according to claim 4, 5, or 6 further contains one or two of Ca: 0.001 to 0.01% and REM: 0.01 to 0.05%. 7. The high-strength bolt friction joining steel material according to claim 1, wherein the steel material is provided with a high-strength bolt.