JP2001087881A - Structure of welded part between vessel body and cover plate or bottom plate, and welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure vessel excellent in fatigure breakage resistance by executing corner-joint welding of a cover plate or a bottom plate to a vessel body under the condition that the pre-calculated welding depth W is obtained. SOLUTION: The cover plate 2 or the bottom plate is corner-joint welded to the cylindrical vessel body 1 and the thickness t(m) of the vessel body 1 decided from a required tensile strength is made to a value T2 higher than the lower limit value t0 of the thickness and the lower limit value of a welding depth is made to W0. On the other hand, a stress intensity factor K(N/m3/2) is calculated according to the equation (1) from a fatigue breaking load P1(N) obtained from the fatigue test of a vessel testing body having the suitable thickness t1 and the welding depth W1, and the welding depth W2 is obtained by substituting the breaking load P(N) and the thickness t2 needed according to the calculated value of the stress intensity factor K for the equation (2). Then the thickness t of the actually welded vessel body is made to >=t2 thickness and the cover plate or the bottom plate is welded to the vessel body with the welding depth W having the value not smaller than the larger value of either of the welding depth W2 or the welding depth lower limit value W0. K=(P1/2t1).(π/W1)1/2... (1), K=(P/2t2).(π/W2)1/2... (2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welded structure having a joint having sufficient strength and fatigue strength against loads such as internal pressure when welding a lid plate or a bottom plate to a container body, and a welding method therefor. .

[0002]

2. Description of the Related Art When a lid plate and a bottom plate are welded to a container body such as a pressure vessel, the lid plate and the bottom plate are fixed to a simple cylindrical container body by welding. As the cover plate or the bottom plate, a member formed into a shape with an edge having the same cross section as the circumferential cross section of the container body can be considered. In the lid plate and bottom plate with molded edges,
It is difficult to form an edge having a shape corresponding to the circumferential cross section of the container body, and it is not easy to align the edge with the peripheral wall of the container body. Further, in a container containing a moving body, smooth movement may be hindered by the generated back bead. Therefore, as shown in FIG. 1, a cover plate 2 or a bottom plate that fits into the container body 1 is prepared, and a square joint welding in which a welding bead 3 is provided between the container body 1 and the cover plate 2 is actually employed. I have. In a container to which internal pressure is repeatedly applied, such as a bottom plate of a strut damper, a lid of a viscous damper, or the like, if the joint strength is not sufficient, breakage or cracking of the welded portion occurs. In this case, the thick container body 1 is used in consideration of safety, since fatigue fracture caused by repeated overloading occurs in the container body, and the fatigue test requires a lot of time and cost.

[0003]

Since pressure vessels such as strut dampers and viscous dampers are used as parts for mounting on vehicles for which weight reduction is strict, they are made of extruded aluminum alloy which is lightweight and excellent in strength. The container body 1 is made, and the lid plate 2 or the bottom plate made of aluminum alloy is
Welding has come to be used. In this regard, the use of the thick container body 1 is a cause of reducing the advantage of weight reduction and increasing the material cost, but is forced to guarantee necessary strength. When a heat-treatable aluminum alloy is used for the container material, the thick container body 1 is used to compensate for a decrease in joint strength due to a heat-affected zone caused by heating during welding. Is not fully utilized. Furthermore, the shape of a welded joint that can withstand a static load can be determined by a conventional method, but the fatigue strength has to be relied on for feeling. This point was also one of the reasons why the unnecessarily thick container body 1 was used.

[0004]

Means for Solving the Problems When the thickness of the container body is set to a normally conceivable value, fatigue failure occurs in the container body, but the cause of the fatigue failure of the joint where internal pressure is repeatedly applied is investigated in detail. As a result, it was found that formation of a deep weld bead is effective for fatigue fracture resistance. The present invention has been completed on the basis of the above findings, and secures the necessary fatigue strength by making the weld bead deep without unnecessarily increasing the thickness of the container body, thereby achieving tensile strength and fatigue strength. It is an object of the present invention to provide a container in which a lid plate or a bottom plate is welded to a container main body with a welded joint excellent in both. In the present specification, the load amplitude defined below is used as the fatigue load P. That is, the average value of the repeated loads applied during the fatigue test [(maximum load + minimum load) / 2] is set as the required specific value, and the load amplitude [(maximum load−minimum load) /
Let 2] be the fatigue load. The fatigue fracture load P refers to a fatigue load that does not break even at a predetermined number of repetitions (usually 10 ⁷ times or more). The welding structure of the present invention, in order to achieve the object, a lid plate or a bottom plate is square joint welded to a cylindrical container body,
Request tensile strength thickness of the container body which is determined from, t (m) is the thickness lower limit value t ₀ or more values t _2, the weld depth lower limit and W _0, whereas appropriate thickness t ₁ and the welding depth W ₁ container specimen fatigue fracture load P ₁ obtained in the fatigue test (N) from equation (1)
The stress intensity factor K (N / m ^3/2 ) is calculated according to the following formula, and the breaking load P required according to the calculated value of the stress intensity factor K
(N) and the thickness t ₂ are substituted into the equation (2) to determine the welding depth W ₂ , the thickness t of the container body to be actually welded is set to the thickness t ₂ or more, and the welding depth W ₂ or the cover plate or the bottom plate to the container body in a larger value than the welding depth W of the welding depth lower limit W ₀ is characterized in that it is welded. _{K = (P 1 / 2t 1} ) · (π / W 1) 1/2 ···· (1) K = (P / 2t 2) · (π / W 2) 1/2 ···· (2 )

A lid plate or a bottom plate is attached to a cylindrical container body by a square joint welding.
When contacting, the wall thickness t of the container body determined from the required tensile strength
(M) is the thickness lower limit value t₀Above value t_TwoAnd the welding depth lower limit
Value W ₀And the thickness t₁And welding depth W₁Container
Fatigue fracture load P obtained by fatigue test of test specimen₁(N)
According to the equation (1), the stress intensity factor K (N / m^3/2)
And fracture required according to the calculated value of stress intensity factor K
Load P (N) and wall thickness t_TwoInto the equation (2)
W_TwoAnd the thickness t of the container body to be actually welded is
t_TwoAnd the welding depth W_TwoOr welding depth lower limit W₀Horse
Under conditions where a welding depth W greater than the larger value is obtained,
By welding the lid plate or bottom plate to the container body, the container body
The lid plate or bottom plate is welded. Further, the lid plate or the bottom plate is
Wall thickness lower limit value t₀The lower limit of the wall thickness for a container body with a wall thickness t equal to
Value t₀Into the equation (2)_TwoOr welding
Depth lower limit value W₀Weld bead deeper than the larger value of
Is welded to the container body under the condition that
Is preferred.

The thickness lower limit value t ₀ for the required tensile strength is:
A container specimen having a weld bead formed at a welding depth deep enough to break the container body or the weld heat-affected zone of the container body than the weld bead portion is subjected to a tensile test, and the obtained breaking load P of the container body is obtained. (N) or the tensile strength σ (N / mm ² ). Lower limit of welding depth W ₀ for required tensile strength
Can be calculated from the known shear strength τ _W (N / mm ² ) of the weld bead determined from the material of the welding wire and the like. Further, the thickness t the thickness t ₂ or more, the weld depth W and the depth W ₂ or more, the container body of the corner portion of the burn-welding depth W to prevent
It is preferable to set the thickness t to be large in relation to the above. The type of the container body and the lid plate or the bottom plate is not limited as long as it is a weldable metal or alloy, but an aluminum alloy is preferable for weight reduction. Among them, an Al-Mg-Si-based aluminum alloy is a suitable material because it has good formability such as extrudability, and can easily produce the container body at low cost.

[0007]

In the corner joint welding, as schematically shown in FIG. 2, there is a butt surface 4 between the materials below a welding bead 3 for fixing the cover plate 2 to the container body 1. When repeated stress is applied, large stress concentration occurs at the lower end 6 of the welded portion, and the stress concentration point becomes a starting point of fatigue failure, and a crack 5 is formed toward the outside of the container body 1, leading to fatigue failure of the container body 1. On the other hand, the welding depth lower limit W ₀ of the wall thickness lower limit t ₀ and the weld bead 3 of the container body 1 from the tensile strength required for the pressure vessel, strength by heat influence upon the strength of the container body 1 (welded Decreasing part H
If there is AZ, the strength can be obtained by ordinary strength calculation from the shear strength of the weld bead 3 and the shear strength of the weld bead 3. It is merely determined for confirmation with W being set. From the results of the investigation by the present inventors, it was found that the form of the fatigue fracture caused by the repeated stress was almost the same as the fatigue fracture of the lap joint of the sheet material formed by laser welding. That is, FIGS. 3 (a) are shown as superimposed laser welded sheet A, the addition repeated tensile shear force F to B, the crack X occurs along the laser weld L _W to the bond. The mechanism of the fatigue fracture of the container in which the lid plate 2 is welded to the container body 1 is the same as that of the fracture caused by the propagation of the crack X into the plate materials A and B.

[0008] Regarding lap joints formed by laser welding, the concept and formula of the stress intensity factor are reported in the 34th Laser Thermal Processing Research Society Transactions (March 1995), pp. 93-100. Therefore, the present inventors have estimated that the concept and formula of the stress intensity factor can be applied to corner joint welding of a pressure vessel. As shown in FIG. 3 (b), the stress intensity factor is the result of deformation occurring in the plate materials A and B when a tensile shear force F is applied.
This is an index indicating the likelihood of crack generation at the stress concentration portion.
The stress intensity factor is determined by the material, the plate thickness T, the welding length w, and the like, and the smaller the value, the better the fatigue resistance. When the concept of the stress intensity factor is applied to the corner joint welding of the pressure vessel, the stress intensity factor K (N / m ^3/2 ) is calculated by the load applied to the thickness t (m) of the container body 1 and the cover plate 2 due to the internal pressure or the like. P
(N) and the depth W (m) of the weld bead 3 are expressed by the above formula (1) or (2) using the factors as factors.

Therefore, the container body 1 having an appropriate thickness t ₁ is provided.
And measuring the fatigue fracture load P ₁ of the corner joints welded preliminary test pressure vessel and a cover plate 2 by welding depth W _1. The measurement of fatigue fracture load P ₁ by substituting in the above-formula (1) determine the stress intensity factor K. Then, like the case of fixing other components to the wall thickness lower limit value t ₀ or container main body 1 described above, the thickness t ₂ by a large wall thickness and the like than a thickness lower limit t ₀ which is determined in consideration of other factors a target fatigue fracture load P into equation (2), given a calculated value mentioned above as the stress intensity factor K, which satisfy the requirements fatigue strength of the weld bead 3 in accordance with the thickness t ₂ of the container body 1 to be used welding depth W ₂ is determined. As a result, the minimum thickness t that satisfies the strength required for the pressure vessel is set to the minimum wall thickness t _0, and the welding depth lower limit W ₀ required for tensile strength or the required welding depth required for fatigue strength. determining the depth W or greater weld depth W deeper than the value of _2,. When the welding bead 3 having the welding depth W of the above depth is formed, a welding joint satisfying the required strength can be obtained. The welding conditions for forming the weld bead 3 deeper than the obtained welding depth W are determined, and the container main body 1 and the cover plate 2 are subjected to corner joint welding. For example, in arc welding such as MIG welding, the depth W of the weld bead 3 can be controlled by the groove depth, welding current, welding voltage, welding speed, and the like. Further, in electron beam welding, laser welding, and the like, the depth W of the weld bead degree 3 can be controlled by controlling the power density and the welding speed.

In this way, by measuring only one joint shape using the preliminary test container, the thickness t of the container body 1 and the weld bead 3 satisfying the required fatigue strength are determined from the shape of the welded portion. Since the depth W is required, the fatigue test that requires a long time can be greatly shortened, and design and design change can be performed at low cost. Further, since it is not necessary to use the thick container body 1 unnecessarily, the pressure vessel can be reduced in weight and the increase in material cost can be suppressed. Above all, the container body 1 is longer than the outer diameter, the weight of the container body 1 increases, and the shape of a pressure vessel such as a strut damper or a viscous damper to which repeated stress is applied can be easily determined, and no back bead occurs. The lid plate 2 and the bottom plate can be welded to the container body 1 by square joint, and the weight thereof can be reduced.

The lower limit value t ₀ of the wall thickness of the container body 1 and the lower limit value W ₀ of the welding depth of the weld bead 3 according to the required tensile strength can be used if they have known values. You can also decide. First, a specimen having a welding depth so deep that the container body 1 or the HAZ (heat affected zone) is broken first is prepared. In the following description, when HAZ destruction occurs, this portion is simply referred to as a container body 1. The container body 1 is subjected to a tensile test, and the strength of the container body 1 is measured. The breaking load P of the container body 1 is related to the outer diameter R ₁ (mm) and the inner diameter R ₂ (mm) of the container body 1 by the formula (3). The outer diameter R ₁ or the inner diameter R ₂ is a value determined from the required shape of the container body 1. Therefore, from the breaking load P (N) and the tensile strength σ (N / mm ² ) of the container body 1 obtained in the tensile test,
Thickness lower limit value t ₀ [t = (R ₁ −R ₂ ) satisfying required characteristics]
/ 2] is calculated. On the other hand, the depth W of the weld bead 3 is determined by the bead breaking load P _W (N) and the bead shear strength τ _W (N / mm
²⁾ and therefore the relationship of the vessel outer diameter R ₁ of formula (4 of the body 1), the welding depth is weld bead 3 is shear failure earlier than the known value or the container body 1 which is determined from the material of the welding wire welding depth lower limit W ₀ determined from of or measurements of the tensile test using a container wall thickness. ^{_{P = σ × (πR 1 2}} -πR 2 2) ···· (3) P W = W × τ W × 2πR 1 ···· (4)

When the welding depth W is increased in accordance with the present invention, a large amount of heat is applied to the material of the joint, and there is a possibility that thermal deformation, burnout, etc. may occur. Defects such as thermal deformation and burnout can be prevented by setting the thickness t of the container body 1 large according to the welding depth W. For example, weld bead 3
The thickness t and the welding depth of the container body 1 are set so that the angle θ between the straight line connecting the deepest portion 6 of the container body 1 and the corner portion 7 of the container body 1 and the inner peripheral surface of the container body 1 is 15 degrees or more. Set W.
When the angle θ is less than 15 degrees, the arc does not sufficiently enter the inside of the material to be welded, and a strong welded joint cannot be obtained. Furthermore,
The heat at the time of welding is transmitted to the entire area of the container body 1 in the thickness direction, and burn-through easily occurs in the corner portions 7 and the like.

[0013]

Embodiment 1 An outer diameter of 60 mm and an inner diameter of 50 were used as the container body 1.
A JIS A6061-T6 aluminum alloy extruded material (thickness t = 5 mm) having a length of 300 mm and a length of 300 mm was used as the cover plate 2 in a JIS A6061 having an outer diameter of 50 mm and a plate thickness of 14.5 mm.
An aluminum alloy disk was used. A V-shaped joint having a groove angle of 50 to 60 degrees was formed between the inner peripheral surface of the container main body 1 and the edge of the lid plate 2, and the lid plate 2 was fitted into the container main body 1 and subjected to corner joint welding. JIS A6061 aluminum alloy is a heat treatment type aluminum alloy in which HAZ is generated near a welded portion. MIG welding was performed using a JIS A5356 welding wire as a filler material, and the welding depth W was controlled by the groove depth, welding speed, and number of passes. When the welded portion was cut in the thickness direction of the lid plate 2 and the welded portion was observed, the groove depth was 4 m.
m, welding current 230A, welding voltage 27V, welding speed 1m
/ Min condition, welding depth W is 4mm, groove depth 6m
m, welding current 230A, welding voltage 27V, welding speed 0.
The welding depth W was 6 mm under the condition of 6 m / min, and the welding depth W was 10 mm under the conditions of a groove depth of 10 mm, a welding current of 230 A, a welding voltage of 27 V, and a welding speed of 0.6 m / min.

An opening for tool insertion is opened at the center of the lid plate 2 welded to the container body 1, the other end of the container body 1 is fixed, and the tool inserted into the opening is connected to an electro-hydraulic servo pulser. A fatigue test was conducted in which the load amplitude was changed at an average load of 17.4 kN and the load was repeatedly applied. As seen in Table 1 of test results, the container having a welded portion of the welded depth W = 4 mm, the fatigue breaking load of 10 ⁷ times was about 3 kN. Formula (1) when the welding depth W is 6 mm and 10 mm
When the fatigue fracture load P is calculated from Equation (2), the values are about 1.22 times and 1.58 times higher than the fatigue fracture load P at a welding depth W of 4 mm. On the other hand, the actual values measured by the fatigue test indicate that the fatigue fracture load P is 3.5 kN (1.2 times) at the welding depth W = 6 mm and the welding depth W = 10 mm.
, The fatigue fracture load P was 5.0 kN (1.7 times), showing high consistency with the calculation results.

[0015]

[0016]

[Embodiment 2] The lid plate 2 is attached to the container body 1 in the same manner as in Embodiment 1.
Was subjected to a tensile test in which a load in the axial direction was applied to the container. As can be seen from the test results in Table 2, the breaking load increased as the welding depth W increased. Further, in the above-mentioned material of the welding wire, the shear strength τ of the welding bead 3 is determined.
Table 2 also shows the results of calculating the breaking load P and the bead breaking load _PW of the container body 1 according to the equation (4) using _W = 145 kN / mm ² . The material used in the embodiment has a HAZ portion. When the welding depth is increased, the HAZ portion on the container body 1 side is broken from the bead portion. However, when the welding depth W is 9.1 mm, the HAZ portion is broken. Destroyed in part. From the breaking load, the strength of the HAZ part is obtained,
Table 2 shows the calculated values of the HAZ breaking load. P <P
_{When W,} the fracture position was in the HAZ, and when P> _PW , the fracture position was in the weld bead 3. Also, the welding depth W
When the relationship between the welding depth W and the fracture load P was arranged, it was found that as shown in FIG. The boundary where the bead fracture changes to the HAZ fracture has a linear relationship with the welding depth W. Even if the welding depth W is increased beyond this boundary, the fracture load P is considered not to increase because the HAZ fracture occurs. . Therefore, in order to obtain the maximum breaking load, it is estimated that a welding depth W of 6.8 mm is necessary.

[0017]

[0018]

As described above, according to the present invention, the cover plate or the bottom plate is attached to the container body under the condition that the welding depth calculated in advance according to the thickness of the container body can be obtained. Since welding is performed, a weld having high fatigue fracture strength is formed. Therefore, the fatigue test, which conventionally took a long time, is greatly reduced, and a container having a highly reliable welded portion can be obtained. The obtained container has excellent fatigue fracture resistance without the need for an unnecessarily thick container body, and is therefore used as a pressure container such as a strut damper or a viscous damper that requires light weight.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a container in which a lid plate is welded to a container body by a square joint.

FIG. 2 is a sectional view of a welded portion.

FIG. 3 is a lap joint of a plate material formed by laser welding (a).
For explaining the deformation (b) of the plate material generated when a tensile shear force is applied to the plate material

FIG. 4 is a graph showing that the boundary from bead fracture to HAZ fracture changes in proportion to welding depth.

[Explanation of symbols]

1: container body 2: lid plate 3: weld bead 4:
Butt surface 5: Crack 6: Deepest part of weld bead 7: Corner part of container body t: Wall thickness of container body W: Weld depth of weld bead
P: Load

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B23K 103: 10 B23K 103: 10 (72) Inventor Motoshi Hotta 1-34-1 Kambara, Kambara-cho, Abara-gun, Shizuoka Prefecture No. Nippon Light Metal Co., Ltd. Group Technology Center F term (reference) 3E072 AA01 CA06 3J046 AA01 BC13 CA01 DA10 EA03 4E068 BA03 DA06 DB04

Claims (8)

[Claims] A cover plate or a bottom plate is welded to a cylindrical container body by a square joint, and the thickness t of the container body determined from a required tensile strength.
(M) is the thickness lower limit value t ₀ or more values t _2, the weld depth lower limit and W _0, whereas obtained in the fatigue tests of appropriate thickness t ₁ and the welding depth W ₁ of the vessel specimens The stress intensity factor K (N / m ^3/2 ) is calculated from the fatigue fracture load P ₁ (N) according to the equation (1), and the required fatigue intensity P (N ) And the wall thickness t ₂ into equation (2) to obtain the welding depth W
₂ calculated, container actually the thickness t of the container body to be welded to the wall thickness t ₂ or more, the weld depth W ₂ or welding depth limit value W larger value than the welding depth W of the ₀ A welded structure between a container body and a lid plate or a bottom plate, wherein a lid plate or a bottom plate is welded to the main body. _{K = (P 1 / 2t 1} ) · (π / W 1) 1/2 ···· (1) K = (P / 2t 2) · (π / W 2) 1/2 ···· (2 ) 2. The thickness t of the container body determined from the required tensile strength when the lid plate or the bottom plate is welded to the cylindrical container body by corner joint welding.
(M) is the thickness lower limit value t ₀ or more values t _2, the weld depth lower limit and W _0, whereas obtained in the fatigue tests of appropriate thickness t ₁ and the welding depth W ₁ of the vessel specimens Calculate the stress intensity factor K (N / m ^3/2 ) from the fatigue fracture load P ₁ (N) according to equation (1), and calculate the required fatigue fracture load P (N) according to the calculated value of the stress intensity factor K. And the thickness t ₂ into equation (2) to obtain the welding depth W
₂ calculated, actually the thickness t of the welded to the container body and the wall thickness t ₂ or more,
Container body and a lid, characterized in that welding the cover plate or the bottom plate to the container body under conditions in which the value or more weld depth W of the larger of the welding depth W ₂ or welding depth lower limit W ₀ is obtained Welding method with plate or bottom plate. _{K = (P 1 / 2t 1} ) · (π / W 1) 1/2 ···· (1) K = (P / 2t 2) · (π / W 2) 1/2 ···· (2 ) Wherein the container body of the same thickness t thicker lower limit t _0, the thickness lower limit t ₀ = by substituting the depth obtained equation (2) as t ₂ W ₂ or welding depth limit welding method of claim 2 container body and the cover plate according or bottom plate for angular joint welding the cover plate or the bottom plate under the conditions deep weld bead from the larger value is formed of the values W _0. 4. A container specimen having a weld bead formed at a deeper welding depth at which the container body or the weld heat affected zone of the container body is destroyed than the weld bead portion is subjected to a tensile test. Breaking load P (N) or tensile strength σ (N / mm
² ) Calculate the lower wall thickness t ₀ for the required tensile strength, and calculate the lower limit W ₀ of the welding depth for the required tensile strength from the known shear strength τ _W (N / mm ² ) of the weld bead. The container body and the lid plate according to claim 2, wherein the lower thickness limit value t ₀ and the lower weld depth value W ₀ of the calculation result are used as the lower thickness limit value and the lower weld depth value determined from the required tensile strength. Welding method with bottom plate. 5. The thickness t is not less than the thickness t ₂ and the welding depth W is not less than the depth W _2, and the thickness is determined in relation to the welding depth W so as to prevent burn-through of the corner portion of the container body. 3. The method for welding a container body and a lid plate or a bottom plate according to claim 2, wherein t is set to be large. 6. The method according to claim 1, wherein a heat-treatable aluminum alloy is used for the container body and the lid plate or the bottom plate. 7. A strut damper obtained by welding a bottom plate to a container body by a square joint using the welding method according to claim 1. 8. A viscous damper in which a lid plate is corner-joint-welded to a container body by the welding method according to claim 1.