JP2017104882A - Through diaphragm weld joint steel pipe column, and manufacturing method of through diaphragm weld joint steel pipe column - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a through diaphragm weld joint steel pipe column not generating breakage of a weld metal prior to a base metal, even when using partial penetration welding to a single bevel groove weld joint.SOLUTION: Assuming that a groove angle of a single bevel groove of a weld zone of partial penetration welding is α(°), a plate thickness of a steel pipe provided with a single bevel groove is t(mm), a distance from the surface to the deepest part of the steel pipe in a weld metal is t'(mm), a weld reinforcement height is e(mm), a tensile strength of the weld metal isσ(N/mm), and a tensile strength of the steel pipe isσ(N/mm), these items satisfy a prescribed relation.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a welded joint steel pipe column including a welded joint, and a manufacturing method thereof, and more particularly, to a through-diaphragm welded joint steel pipe column by partial penetration welding of a single bevel groove weld and a manufacturing method thereof.

  A steel pipe column with a diaphragm welded joint is formed by welding with a T-shaped joint over the entire circumference so that the small end (end face) of the steel pipe and the surface of the diaphragm are brought together. In such a steel pipe column, when a tensile stress is applied to the welded portion, it is necessary to configure the fracture to occur first from the side of the steel pipe, which is the base material, instead of the weld metal.

  In the case of through-diaphragm welded jointed steel pipe columns, a full groove welding is generally performed. However, the complete groove welding of the reshape groove requires the installation of the backing metal and the management of the root gap (the size of the gap between the end surface of the steel pipe and the diaphragm surface) in the assembly process. Make it complicated.

  On the other hand, if partial penetration welding can be used, attachment of a backing metal and management of a route gap are unnecessary, and convenience is high. However, when partial penetration welding is used, an unwelded portion is formed on at least a part of the root side. Therefore, according to the conventional joint strength evaluation, it could not be used as a full strength welded joint (that is, a welded joint for through-diaphragm welded steel pipe columns).

  Patent Document 1 discloses a technique characterized in that a lip is formed at the lower end of a base material in a groove welded joint. According to this, the route gap management by the backing metal can be omitted by providing the lip-shaped protrusion on the root portion of the groove. Moreover, the amount of welding can be reduced by narrowing a groove | channel compared with the conventional full penetration welding.

  Further, Patent Document 2 discloses that in complete penetration welding, even in the case of undermatching (the tensile strength of the weld metal material is lower than the tensile strength of the base material), the weld metal part is prevented from being broken. A technique for obtaining a tenacious welded joint by breaking it is disclosed.

JP-A-9-174238 Japanese Patent Laying-Open No. 2015-91599

However, the invention described in Patent Document 1 requires welding on the inner surface side, and the welding torch cannot access the inner surface side when the closed cross section is covered with a plate like a through-diaphragm welded joint of a steel pipe column. Not applicable.
Moreover, the invention described in Patent Document 2 is limited to complete penetration welding and cannot be applied to partial penetration welding joints.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a through-diaphragm welded joint steel pipe column that does not cause the weld metal to break before the base metal even when partial penetration welding is used for the labyrinth welded joint. Moreover, the manufacturing method of the said through-diaphragm welded joint steel pipe column is provided.

  The present invention will be described below.

The invention according to claim 1 is a through-diaphragm welded joint structure in which a steel pipe is welded to a through-diaphragm, wherein the groove angle of the reshape groove of the partially penetration welded portion is α (°), and the reshape opening is performed. The thickness of the steel pipe provided with the tip is t (mm), the distance from the surface of the steel pipe to the deepest part of the weld metal is t '(mm), the extra height is e (mm), and the tensile strength of the weld metal When the _thickness is _WM σ _u (N / mm ² ) and the tensile strength of the steel pipe is _BM σ _u (N / mm ² ),
And,
It is a through-diaphragm welded joint steel pipe column. However, β is 0 or more and β ′ satisfying the following formula or the smaller one of the α values.

The invention according to claim 2 is the through-diaphragm welded joint steel pipe column according to claim 1, wherein the tensile strength of the weld heat affected _zone is _HAZ σ _u (N / mm ² ).
Meet.

The invention according to claim 3 is the through-diaphragm welded joint structure according to claim 1 or 2, wherein the steel pipe is a cold-formed square steel pipe, and the tensile strength of the corner of the cold-formed square steel pipe is _expressed as _cBM. σ _u (N / mm ² ), when the tensile strength of the base material before cold forming is _fBM σ _u (N / mm ² ),
as well as,
Is established.

The invention according to claim 4 is a method of manufacturing a through-diaphragm welded joint structure in which a steel pipe is welded to a through-diaphragm by partial penetration welding, and the groove angle of the reshape groove of the partial penetration welded portion is set. α (°), t (mm) for the thickness of the steel pipe provided with the lathe groove, t ′ (mm) for the distance from the surface of the steel pipe to the deepest part of the weld metal, and e ( mm), when the tensile strength of the weld metal is _WM σ _u (N / mm ² ), and the tensile strength of the steel pipe is _BM σ _u (N / mm ² ),
And,
This is a method of manufacturing a through-diaphragm welded jointed steel pipe column in which welding is performed by determining a groove depth before welding so as to satisfy the above condition. However, β is 0 or more and β ′ that satisfies the following expression or the smaller one of the α values.

Invention of Claim 5 is the manufacturing method of the through-diaphragm welded joint steel pipe column of Claim 4, When the tensile strength of a welding heat affected _{zone is set} to _HAZ (sigma) _u (N / mm _< ² >),
Welding is performed to further satisfy

The invention according to claim 6 is the method of manufacturing a through-diaphragm welded joint structure according to claim 4 or 5, wherein the steel pipe is a cold-formed square steel pipe, and the tensile strength of the corner of the cold-formed square steel pipe is When the _thickness is _cBM σ _u (N / mm ² ) and the tensile strength of the base material before cold forming is _fBM σ _u (N / mm ² ),
as well as,
Welding is performed so that

  According to the present invention, it is possible to provide a through-diaphragm welded jointed steel pipe column that does not cause the weld metal to break before the base metal even when partial penetration welding is used for the reshape groove welded joint.

FIG. 1 is an external perspective view of a through-diaphragm welded joint structure 10. 1 is a view showing a cross section of a through-diaphragm welded joint structure 10. FIG. It is the figure which expanded a part of welding part 20. FIG. It is a figure explaining the welding part. It is a figure showing the ntw coordinate system. 6A shows an example in which the welded portion 20 is modeled and has no undissolved portion, and FIG. 6B shows an example in which the welded portion 20 is modeled and has an undissolved portion. FIG. 7A is a diagram for explaining a model used for the destruction of the base material. FIG. 7B is a two-dimensional coordinate system, and FIG. 7B is a display using the nt-w orthogonal coordinate system. It is a figure explaining the model used for the fracture | rupture along a groove | channel, and is a two-dimensional coordinate system. It is a figure explaining the model used for destruction of a weld metal, and is a two-dimensional coordinate system. It is a figure showing the relationship between a groove angle and a penetration depth ratio lower limit. It is a figure showing the relationship between a penetration depth and a matching lower limit. It is a figure explaining a steel pipe corner. It is a figure explaining the relationship between the tensile strength of the flat steel material before cold work, and the tensile strength of a steel pipe corner. It is a figure explaining an analysis model.

  The present invention will be described below based on embodiments shown in the drawings. However, the present invention is not limited to these forms.

  FIG. 1 is a view for explaining one example of the form, and is a perspective view schematically showing the appearance of a through-diaphragm welded jointed steel pipe column 10. FIG. 2 is a cross-sectional view taken along a line indicated by II-II in FIG. 1 (that is, one cut in a direction along the longitudinal direction of a through-diaphragm welded joint steel pipe column). FIG. 3 is an enlarged cross-sectional view paying attention to the portion indicated by III in FIG.

  As can be seen from FIGS. 1 to 3, in this embodiment, the through-diaphragm welded joint steel pipe column 10 includes a square steel pipe 11, a dice (sometimes referred to as a Tyco) 12, a beam 13, and a diaphragm 14. Yes. As can be seen from this, in this embodiment, the through-diaphragm welded joint steel pipe column 10 is a square steel pipe column using a through-diaphragm weld joint.

  In the through-diaphragm welded jointed steel pipe column 10, a dice 12 is arranged between two opposing end surfaces (small openings) of two rectangular steel pipes 11 arranged coaxially. The dice 12 is also a square steel pipe as a shape. As a result, two portions where the end surface of the dice 12 and the end surface of the square steel pipe column 11 are opposed to each other are formed, and a diaphragm 14 is provided here. The diaphragm 14 is a plate-like steel material having an outer shape larger than that of the square steel pipe 11 and the dice 12, one plate surface is welded to the end surface of the square steel tube column 11, and the other plate surface is welded to the end surface of the dice 12. ing. Accordingly, as can be seen from FIGS. 1 to 3, the outer periphery of the diaphragm 14 protrudes from the outer periphery of the square steel pipe 11 and the dice 12.

  As can be seen from FIGS. 1 to 3, in the welded joint of the through-diaphragm welded joint steel pipe column 10 of the present embodiment, the square steel pipe 11 and the end face of the dice 12 are attached to the front and back surfaces of the diaphragm 14. The welded portion 20 is formed by welding with the weld metal 21 at the part. The welded portion 20 is provided over the entire line (the entire circumference) of the abutted portion. In the present invention, the welded portion 20 is formed by partial penetration welding, and no backing metal is disposed on the side opposite to the welded portion 20. Hereinafter, the welded portion 20 will be described in more detail.

  As can be seen from this figure, a part of the end surface of the base material that is the square steel pipe 11 is inclined with respect to one surface of the diaphragm 14, and a partial re-shaped groove is formed. The other part is formed so as to overlap with one surface of the diaphragm 14. The weld metal 21 is joined to the partial groove of the diaphragm 14 and the square steel pipe 11 with the weld metal 21 interposed therebetween. At this time, the following shapes and values are defined. A schematic diagram is shown in FIG.

Steel pipe thickness: t (mm)
Extra height: e (mm)
Thickness from steel pipe surface to unwelded part (welded part thickness): t ′ (mm)
Groove angle: α (°) (0 ° ≦ α <90 °)
Tensile strength of steel pipe: _BM σ _u (N / mm ² )
Tensile strength of weld metal: _WM σ _u (N / mm ² )

  And in this invention, Formula (1) and Formula (2) are materialized.

  Here, β (°) in the formula (2) represents an angle at which fracture occurs in the weld metal, and 0 ≦ β ≦ α. Therefore, β is the smaller of β ′ and α satisfying the following formula (3) Take the value of.

  Equations (1) to (3) will be described later, but the need for a weld metal to break with the base metal (steel pipe) without breaking with the weld metal in the weld portion of the partial penetration welding of the steel pipe Represents strong strength. According to this, in the through-diaphragm welded jointed steel pipe column 10, even when partial penetration welding is used in the welded portion, the base metal (steel pipe) is broken prior to being broken by the weld metal. be able to. Therefore, as long as this is satisfied, it is possible to apply partial penetration welding in a through-diaphragm welded joint steel pipe column by applying known materials and known welding conditions, and using a backing metal and adjusting the root gap Is no longer necessary. In addition, satisfying this condition also means improving the reliability of performing more appropriate welding. In this case, special measures such as improving the fracture toughness of the weld metal are not required. For example, it is not necessary to apply a weld metal that is stronger and more expensive than necessary.

Here, as a means for more easily obtaining the tensile strength _BM σ _u (N / mm ² ) of the steel pipe 11 and the tensile strength _WM σ _u (N / mm ² ) of the weld metal, calculation from the respective Vickers hardness is performed. Can be mentioned. Specifically, equations (4) and (5) may be calculated. Equations (4) and (5) represent Hv and tensile strength as a relational expression based on a conversion table of Vickers hardness Hv and tensile strength in the literature (SAE International, SAE J 417, 1983). Is.

_WM Hv in the equation is the Vickers hardness (Hv) of the weld metal 21, and _BM Hv is the Vickers hardness (Hv) of the steel pipe. Further, the measurement of the Vickers hardness uses a value obtained based on JIS Z2244: 2009 at a position 2 mm deep from the outer surface of the weld metal 21 of the steel pipe 11a and the welded portion 20.

  Next, the grounds of Expression (1) to Expression (3) will be described. That is, in a through-diaphragm welded jointed steel pipe column using partial penetration welding, the strength to be provided for each part to be broken by the steel pipe as a base material was obtained by ultimate analysis without being broken by the weld metal of partial penetration welding.

Here, the following (i) to (v) are assumed.
(I) The fracture condition of Expression (10) is established, in which the yield stress σ _y in the Von Mises yield condition is replaced with the tensile strength σ _u obtained from the uniaxial tensile test.

Here, σ ₁ , σ ₂ , and σ ₃ are main stresses in a three-dimensional stress state. Furthermore, in order to describe the fracture condition of the equation (10) by stress with respect to an arbitrary coordinate system, when the nt-w orthogonal coordinate system shown in FIG. 5 is set, six stress components (σ _n , σ of each coordinate are set. _{(t 1} , σ _w , τ _nt , τ _tw , τ _wn )).

(Ii) The weld length is sufficiently larger than the bead width, and the weld line does not expand or contract at the fracture surface. That is, the vertical strain in the weld line direction is zero.
(Iii) It is assumed that only the tensile force in the axial direction is acting on the joint.
(Iv) Like the welds shown in FIGS. 6 (a) and 6 (b), the welded portion has a re-shaped groove, the base metal plate thickness on the side where the groove is provided is t (mm), and the weld metal Among them, the distance from the surface of the base material to the deepest part (penetration depth) t ′ (mm), the groove angle α (°), and the surplus height are e (mm). 6 (a) shows an example in which the unwelded portion is composed only of the root face (surface on which the base material is attached to the other material), and FIG. 6 (b) shows the unwelded portion in the unwelded portion (open). This is an example consisting of a portion where the weld metal has not melted (usually a gap) and a root face. In any case, the unwelded portion can be calculated by tt ′.
(V) Both the weld metal and the base metal are assumed to have uniform strength within each region.

  Next, calculate the maximum proof stress after modeling the fracture mechanism for each of the three fractures: fracture of the base metal, fracture of the base metal along the groove, and fracture of the weld metal. And derive the relational expression. Each will be described below.

<Fracture strength of the entire thickness of the base material>
FIG. 7 shows a model used for breaking the entire thickness of the base material. The original shape is shown in FIG. However, the example of FIG. 6B is the same. FIG. 7A shows a display using a two-dimensional coordinate system, and FIG. 7B shows a display using an nt-w orthogonal coordinate system.
As shown in FIG. 7 (a), the displacement speed of the load acting direction and u ₁ in motor acceptability condition breaking locations, and θ the angle of fracture mechanism occurs with respect to the thickness direction. Further, as shown in FIG. 7B, the n-axis is orthogonal to the fracture mechanism, the t-axis is perpendicular to the fracture mechanism, and the w-axis is perpendicular to the weld line. Take the coordinate system ntw. Then, the velocity components in the direction along the fracture mechanism (t direction) and the direction orthogonal to the direction (n direction) are u ₁ · sin θ and u ₁ · cos θ, respectively. Since the normal stress σ _{t in the} t-axis direction is regarded as 0, if σ _t = 0 is substituted into the above equation (11) and the tensile strength of the base material is _BM σ _u , the fracture condition is the equation (12 ).

In the fracture mechanism shown in FIG. 7A, the strain ε _{w in} the w-axis direction is 0, the shear strain γ _{tw in the tw} plane is 0, and the shear strain γ _{wn in the wn} plane is 0. 12) and the normal flow law of plastic flow, the relationship shown in equation (13) holds.

  By substituting equation (13) into equation (12), the destructive conditional equation becomes equation (14).

Here, the stress work increment W _i1 in FIG. 7A per unit length (= 1) shown in FIG. 7B is expressed by Expression (15).

Here, the stresses σ _n and τ _nt satisfy Expression (14) which is a fracture condition. From the normal law of plastic flow, u ₁ · cos θ and u ₁ · sin θ are as shown in Equation (16).

From Expression (16), τ _nt is expressed as Expression (17) using σ _n .

By _calculating σ _n and τ _nt as in Expression (18) from Expression (14) and Expression (17) and substituting them into Expression (15), the stress work increment becomes as in Expression (19).

On the other hand, the work increment W _ex1 due to the external force is expressed by Expression (20), where _PBM1 is the fracture resistance of the entire thickness of the base material when the weld line direction (w direction) is the unit length.

Since the equation (19) is equal to the equation (20) based on the principle of virtual work, the equation (21) is obtained by solving for _PBM1 .

Since θ which minimizes the equation (21) is 0, the fracture proof strength relating to the fracture mechanism FIGS. 7A and 7B is expressed by the equation (22) using t and _BM σ _u .

<Fracture strength along the groove of the base material>
FIG. 8 shows a model used for fracture along the groove in the base material. This is a diagram corresponding to FIG. Thereby, the fracture strength is calculated. Since the displacement speed in the load acting direction is u ₂ and the angle at which the fracture mechanism is generated coincides with the groove angle α, the stress components in the direction along the fracture mechanism and in the orthogonal direction are u ₂ · sin α and u ₂ · cos α, respectively. Become. Following the above example, the orthogonal coordinate system nt-w is used for the fracture mechanism, where n is the orthogonal direction of the fracture mechanism, t is the direction along the fracture mechanism, and w is the direction parallel to the weld line. . As in the case of the fracture of the total thickness of the base material, the normal stress σ _{t in the} t-axis direction is 0, the strain ε _{w in the} w direction is 0, the shear strain γ _{tw in the tw} plane is 0, and the shear in the wn plane is Assuming that the strain γ _wn is 0, the fracture condition equation is expressed by equation (14), where _BM σ _u is the tensile strength of the base material. The stress work increment W _i2 in FIG. 8 per unit length in the weld line direction is expressed by the following equation (23).

Here, the stresses σ _n and τ _nt satisfy Expression (14) which is a fracture condition. From the normal law of plastic flow, σ _n and τ _nt can be considered in the same manner as in the case of the destruction of the full thickness of the base material, and can be expressed by an expression in which θ in Expression (18) is replaced with α. Substituting into, the stress work increment is given by the following equation (24).

Here, l _cr2 is represented by the following formula (25).

On the other hand, work increment W _ex2 by external force, the fracture strength along the open destination base material per weld line direction unit length of the weld joint and P _BM2, the following equation (26).

Based on the principle of virtual work, assuming that equation (24) and equation (26) are equal, and substituting equation (25), P _BM2 is expressed by the following equation (27) using t ′, α, and _BM σ _u. .

<Fracture strength of weld metal>
A model used for fracture of the weld metal is shown in FIG. FIG. 9 is a diagram corresponding to FIG.
The plastic deformation increment in the load acting direction is u ₃ and the angle at which the fracture mechanism occurs is β (0 ≦ β ≦ α). Following the example of FIG. 7B, with respect to the fracture mechanism, n is the orthogonal direction of the fracture mechanism, t is the direction along the fracture mechanism, and w is the direction parallel to the weld line. Take w. Then, as in the case of the base material the total thickness of the fracture above, the t-axis direction of the normal stress sigma _t 0, the w direction strain epsilon _w is 0, t-w shear strain [gamma] t _w in the plane 0, w Assuming that the shear strain γ _wn in the −n plane is 0, the fracture condition equation is obtained by replacing the base material tensile strength of Equation (14) with the tensile strength _WM σ _u of the welded portion, and Equation (28).

The stress work increment W _i3 in the fracture mechanism FIG. 9 per unit length in the weld line direction can be expressed by the following equation (29).

Here, the stresses σ _n and τ _nt satisfy Expression (28) which is a fracture condition. From the normal law of plastic flow, σ _n and τ _nt can be expressed by an expression in which θ in Expression 18 is replaced with β. Therefore, when substituting into Expression (29), the stress work increment becomes the following Expression (30).

Here, l _cr3 is represented by the following formula (31).

On the other hand, the work increment W _ex3 due to the external force is expressed by the following equation (32), where _PWM is the proof stress of the weld metal per unit length in the weld line direction of the weld joint.

Based on the principle of virtual work, assuming that equation (30) and equation (32) are equal and substituting equation (31), P _WM uses t ′, α, e, β, _WM σ _u and the following equation (33 ).

When the expression (33) is the minimum, the fracture mechanism is the fracture strength of the weld metal corresponding to FIG. 9. The expression (33) is partially differentiated by β to obtain ∂P _WM / ∂β = 0 and solved for β. And the following equation (34). When β satisfying the following expression (34) is obtained, the true value of _PWM is obtained.

<Conditions not to break along the base metal groove and weld metal part>
Depth t ′ (necessary penetration depth) from the groove side surface of the base metal to the weld metal root part for the destruction of the full thickness part of the base material before the fracture along the base material groove is expressed by the equation (22). When the equation (27) is solved as P _BM1 <P _BM2 , the above equation (1) is obtained.
On the other hand, when the condition of the weld metal for the base metal to break prior to the welded part is solved as P _BM1 <P _WM from the formulas (22) and (33), the above formula (3) is obtained.

  FIG. 10 shows the ratio of the required penetration depth with respect to the groove angle α (t ′ / t when the left side of the equation (1) is equal to the right side) in order to cause the full thickness portion of the base material to break. The solid line indicates the boundary of the fracture mechanism shown in FIGS. 7 and 8. If the penetration depth is in the region above this line (open section), the full thickness of the base material is destroyed, and if the region is below this line This indicates that the fracture occurs along the groove of the base material. From FIG. 10, when the groove angle α is 35 degrees, if the penetration depth is about 94% or more with respect to the base material plate thickness, the entire thickness of the base material is broken, that is, the fracture along the base material groove. Does not happen. It can also be seen that the narrower the groove, the greater the penetration depth is required to achieve the destruction of the entire thickness of the base material.

FIG. 11 shows the lower limit of the weld metal strength to base metal strength ratio ( _WM σ _u / _BM σ _u ) with respect to the penetration depth ratio t ′ / t in order to cause the full thickness of the base metal to break. (When the left side of (2) is the right side). The solid line is an example in which the base material plate thickness t is 32 mm and the groove angle α is 35 °. From FIG. 11, it can be seen that the greater the groove angle, the smaller the penetration depth, and the greater the penetration depth, the more relaxed the matching lower limit of weld metal strength.

In addition to the above, destruction along HAZ (heat affected zone) may be assumed. In this case, the HAZ tensile strength _HAZ σ _u is used instead of the weld metal tensile strength _WM σ _{u in} the equation (2). In this case, since the fracture angle β coincides with the groove angle α, the following formula (35) is established as the required strength of the HAZ for breaking with the base material without breaking with the HAZ.

  By satisfying this equation (35), even if the HAZ is softened, the base material can be destroyed as long as this relationship is satisfied.

Here, calculation from Vickers hardness can be mentioned as a means for obtaining the tensile strength _HAZ σ _u (N / mm ² ) of _HAZ more simply. Specifically, a Vickers hardness test is performed based on JIS Z2244: 2009 at a position on the inner surface side of 2 mm from the outer surface, and Equation (36) may be calculated from the minimum value of the measured values.

In addition, when the steel pipe and dice are square steel pipes, the strength is higher at the corners compared to other parts, and fractures often occur from one of the corners. Good. However, the idea is the same as above, and the formula (3) may be replaced with the following formula (37) with the tensile strength of the steel pipe corner being _cBM σ _u .

  Here, the “corner” of the steel pipe is considered as follows. FIG. 12 shows a diagram for explanation. FIG. 12 is a view in which a through-diaphragm welded joint steel pipe column 10 is viewed from the direction indicated by the arrow XII in FIG.

As can be seen from FIG. 12, the square steel pipe 11 has a square cross-sectional shape, but actually, so-called fillets (also referred to as R (R)) are formed at the four corners of the square, and has an arc shape. .
Here, in the center line C of the plate thickness of the square steel pipe 11 as shown in FIG. 12, the center of the formed arc is represented by O, and when the apex of the square when the arc is not formed is A, The part of the range (total 65 degrees) which becomes 32.5 degrees on one side and the other side across the line OA is defined as a corner (steel pipe corner) of the square steel pipe 11. The radius of curvature of the steel pipe corner is not particularly limited, but when the radius of curvature on the outside of the steel pipe corner is r and the plate thickness of the steel pipe is t ₁ (mm), in 6 ≦ _{t 1} ≦ 9 in _{3.0t 1 ≦ r ≦ 4.0t 1,} 19 <t 1 is managed by 3.1t ₁ ≦ r ≦ 3.9t _1. On the other hand, in the square steel pipe formed with a cold roll, 2.0t ₁ ≦ r ≦ 3.0t ₁ is managed.

Furthermore, as another means for obtaining the tensile strength _cBM σ _u (N / mm ² ) of the steel pipe corner 11, the tensile strength at the steel pipe corner can be actually obtained in accordance with JIS Z2241: 2011. It can also be obtained from the cold working before the flat steel tensile strength ^{_{f BM σu (N / mm 2}} ) using the following equation (38). That is, the tensile strength of the steel pipe corner is obtained from the tensile strength of the material forming the square steel pipe.

This equation (38) was obtained as follows. That is, in accordance with JIS Z2241: 2011, the tensile strength _fBM σ _u (N / mm ² ) of a flat steel material before cold working is measured, and a square steel pipe is manufactured using this steel material. The tensile strength _c BMσ _u (N / mm ² ) of the corner of the steel pipe is measured in accordance with JIS Z2241: 2011 for this manufactured square steel pipe, and compared with _fBM σ _u (N / mm ² ). Table 1 shows the conditions and results, and FIG. 13 shows a graph of the results.

In Table 1, the material, plate thickness, and mechanical quality of each specimen were shown.
The graph of FIG. 13 is a tensile strength of flat steel before cold working horizontal axis ^{_{fBM σ u (N / mm 2}} ), tensile strength of the steel pipe corners on the vertical axis ^{_{cBM σ u (N / mm 2}} ) I took it.

  As shown in FIG. 13, the formula (39) indicated by the broken line is obtained by the method of least squares based on the result of Table 1. On the other hand, in consideration of the safety side as a structure, 2σ is added to the equation (39) in consideration of the standard deviation σ of the error between the equation (39) and each measured value, and this is expressed by the equation (38). ).

Further, when the through-diaphragm welded joint steel pipe column is manufactured, the through-diaphragm welded joint steel pipe column may be manufactured so as to satisfy the above relationship. However, in this case, the thickness t ′ (mm), which is the thickness from the surface of the square steel pipe to the unwelded part (welded part thickness) in formulas (1) and (2), is obtained so that it is obtained after welding. The tip depth t ′ ₀ is set in advance.

In the above example, a square steel pipe is applied as the steel pipe, but the steel pipe may be a round steel pipe. Even a round steel pipe can be considered similarly. The above-mentioned matters can be considered in the same way regardless of the material (strength level) of the steel material. That is, normally used as a material for the steel pipe columns may be considered in the same manner for any steel 490 N / mm ² class steels ~590N / mm ² grade steel.

In the examples, analysis was performed by numerical analysis assuming a three-point bending test. FIG. 14 shows the analysis model. Taking account of geometric symmetry, a quarter of the entire specimen was modeled. Table 2 shows the forms of steel pipes and welds. In this analysis, 490 N / mm grade ² TMCP (Thermo-Mechanical Control Process) steel is used as a material property. And the full thickness tensile test of a corner | angular part and the round bar tensile test result of the weld metal were used. The form of the through-diaphragm welded part is No. No. 1 was complete penetration welding, the groove angle α was 35 °, the root gap g was 7 mm, and the surplus height e was 8 mm (1/4 t). No. 2-No. 5 is partial penetration welding, and therefore the root gap g is 0 mm. Four types of penetration depth t ′ were prepared. 2 is 32 mm. 3 is 31 mm. 4 is 28 mm. 5 is 25 mm. From formula (1) and formula (2), the minimum penetration depth required to satisfy these conditions is 30.2 mm. 2 and no. 3 satisfies the formulas (1) and (2). 4 and no. 5 does not satisfy this.

  As a result of the above analysis, No. 1 which does not satisfy Expression (1) and Expression (2). 4 and no. In FIG. 5, the equivalent stress and the equivalent strain might concentrate on the weld metal, and this did not occur under other conditions.

DESCRIPTION OF SYMBOLS 10 Through-diaphragm welded joint structure 11 Steel pipe 12 Dice 13 Beam 14 Diaphragm 20 Welding part 21 Weld metal

Claims (6)

A through-diaphragm welded joint structure formed by welding a steel pipe to a through-diaphragm,
The groove angle of the reshape groove of the partial penetration weld is α (°), the plate thickness of the steel pipe provided with the reshape groove is t (mm), and the deepest part of the weld metal from the surface of the steel pipe To t ′ (mm), extra height e (mm), weld metal tensile strength _WM σ _u (N / mm ² ), and steel pipe tensile strength _BM σ _u (N / Mm ² )
And,
A through-diaphragm welded steel pipe column.
However, β is 0 or more and β ′ that satisfies the following expression or the smaller one of the α values.
When the tensile strength of the weld heat affected _zone is _HAZ σ _u (N / mm ² ),
The through-diaphragm welded jointed steel pipe column according to claim 1, wherein: The steel pipe is a cold-formed square steel pipe, the tensile strength of the corner of the cold-formed square steel pipe is _cBM σ _u (N / mm ² ), and the tensile strength of the base material before cold forming is _fBM σ _{When u} (N / mm ² ),
as well as,
The through-diaphragm welded joint structure according to claim 1 or 2, wherein: A method of manufacturing a through-diaphragm welded joint structure in which a steel pipe is partially melt welded to a through-diaphragm and welded,
The groove angle of the reshape groove of the partial penetration weld is α (°), the plate thickness of the steel pipe provided with the reshape groove is t (mm), and the deepest part of the weld metal from the surface of the steel pipe To t ′ (mm), extra height e (mm), weld metal tensile strength _WM σ _u (N / mm ² ), and steel pipe tensile strength _BM σ _u (N / Mm ² )
And,
A method for manufacturing a through-diaphragm welded steel pipe column, in which the groove depth before welding is determined so as to satisfy the requirements.
However, β is 0 or more and β ′ that satisfies the following expression or the smaller one of the α values.
When the tensile strength of the weld heat affected _zone is _HAZ σ _u (N / mm ² ),
The manufacturing method of the through-diaphragm welded joint steel pipe column of Claim 4 which welds so that it may satisfy | fill further. The steel pipe is a cold-formed square steel pipe, the tensile strength of the corner of the cold-formed square steel pipe is _cBM σ _u (N / mm ² ), and the tensile strength of the base material before cold forming is _fBM σ _{When u} (N / mm ² ),
as well as,
The manufacturing method of the through-diaphragm welded joint structure according to claim 4 or 5, wherein welding is performed so that