JPS60116725A - Continuous local heat treatment of steel pipe - Google Patents

Abstract

PURPOSE:To carry out the satisfactory local annealing or normalization of an electric welded pipe without roughening the structure by arranging a high frequency heating coil, a medium frequency heating coil and a high frequency heating coil each having a prescribed width and length in series and by moving the seam part of the electric welded pipe under the coils so as to adjust the inside and outside of the heated part to a specified temp. range. CONSTITUTION:A high frequency heating coil 5, a medium frequency heating coil 4 and a high frequency heating coil 3 each having a prescribed width and length are arranged in series at uniform intervals, and the seam part of an electric welded pipe 1 is moved just under the coils at a constant speed in the axial direction. The outside of the pipe 1 is rapidly heated with the coil 3, the inside is also heated with the coil 4, and the outside is rapidly heated again with the coil 5. The outside is not heated to >=1,000 deg.C at which the structure is roughened, and the inside and outside of the seam part are adjusted to a narrow proper annealing or normalizing temp. range, so satisfactory heat treatment is carried out.

Description

[Detailed description of the invention] The present invention relates to a method for local continuous heat treatment of steel pipes.

It has already become common to sinter or standardize an ERW tube seam using an ERW tube welding line.

Assuming that the power of the welding equipment in the welding line is approximately 600 kW, it would take approximately 20 kW to give the welding equipment a sintering capacity that matches the welding capacity.
Approximately 0.00 M of power is required.

For this reason, there is a problem in that the sintering power of the welding device becomes extremely large. Furthermore, it is well known that if the seam portion is raised to a certain temperature or higher without increasing the temperature difference between the inner and outer surfaces of the electric resistance welded tube, the metal properties of the surface will deteriorate. That is, when the temperature of the seam portion is raised to 1050°C or higher, the metal crystal grains become coarse and the strength is reduced, and when the temperature is set to lower than 950°C, there is a problem that the toughness is not recovered.

The present invention has been made to solve the above problems.
'TiV sewn pipe bathing pipe bathing line is a steel pipe that maintains the temperature difference between the inner and outer surfaces of the seam part at a predetermined value to prevent deterioration of the gold IQ characteristics of the seam part and saves power. The purpose of the present invention is to provide a local continuous heat treatment method.

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention. In the figure, / is an electric resistance welded tube with a wall thickness of 12 g or more, which is being transported in the direction of the arrow λ shown in the figure. 3゜Hiro, J is a pure fired inductor, standard length 400iW to 1500mm, these inductors 3. The groups, j are arranged in series at predetermined intervals. The arrangement is set so that the time required for a predetermined portion of the electric resistance welded pipe to pass between the rust conductors (heat penetration time) is 5 seconds or more. ml ripening heat penetration time T) is determined by the following formula.

T) 9.5X 10=Xt' However, t is the wall thickness of the tube.

Inductors arranged as described above3. A current of a predetermined frequency is supplied to μ and S from a high frequency inverter t and a medium frequency inverter 7. That is, the average temperature of the seam of the tube at the inlet of the inductor 3 is 600°C to 700°C.
A high frequency current of 700 H2 to 8000 Hz is supplied to the inductor μ until the average temperature at the seam of the tube at its entrance reaches 700°C to 750°C. The inverter 6.7 is set so as to supply the inductor S with a high frequency current of 700H2 to 8000Hz.

Next, we were able to improve the accuracy of the simulation by comparing the needle simulation results for the ERW pipe seam with the actual re-simulation knots. Tables 1 and 2 show the results of simulations conducted with respect to the width of the conductor.

Table 1 Table 2 From the above results, it is possible to increase total efficiency and reduce costs by narrowing the conductor width of the inductor, increasing the frequency of the current applied to the inductor, and reducing the number of inductor stands. There are prospects for a decline. Based on the above evaluation, the results of experiments were conducted taking into account the arrangement of the inductor. Figures 2 to 4 show the experimental results. In addition, in FIGS. 2 to 4, experiments were conducted using examples using four and six inductors.

Figure 2 shows an electric resistance welded tube with an outer diameter of 406 mm and a wall thickness of 15.9 mm.
Length 900111B+7) 44 children J/ ~,? Hiromu is my husband
1800e, 1250Mm.

Arrange them in series with an interval of 1450M, and keep a gap between each inductor J/~3hiro and the electric resistance welded tube. When set to 6 words, heating power P supplied to inductors 37 to 3ψ
In addition to selecting G(1&), the frequency f (, Hi) of the heating current, and the conductor width W (m) of the inductor as shown in Table 8, when the heating time is 488 sec and the cooling time is 6 (6), The relationship between the arrangement position of the inductor in the axial direction of the ERW tube and the temperature between the outside l111 and the inner surface of the ERW tube seam portion is shown.

The difference between FIG. 8 and FIG. 2 is that the fiI conductor I
In addition, the distance between the inductors 3 and 35 is set to 1.
500111, the frequency of the power supplied to the II conductors 31 to 35, and the conductor width of the inductor are selected as shown in Table 4, the arrangement position of the inductor in the axial direction of the ERW tube and the ERW Shows the temperature relationship between the outer and inner surfaces of the weld.

Table 4 Also, the difference between Figure 4 and s jlIW is that when the number of waves per station of power supplied to inductors 37 to 3 and the conductor width of the inductor are determined as shown in Table 5, ≧ There,
The relationship between the position of the inductor in the axial direction of the electric resistance welded tube and the temperature between the outer surface and the inner surface of the electric resistance welded part is shown.

As described above, the following has become clear from the first to third experimental examples.

(11 The heat treatment temperature for the outside and inside of the ERW pipe is i, ooo
C) and 900 degrees Celsius, the power applied to the inductor can be reduced from about 2,200 degrees to about 1620 degrees by making the inductor conductor width 85 words or C) 24s+s.

(2) In order to suppress the temperature difference between the inner and outer surfaces at the seam portion of the final heating inductor to 100°C immediately after heating, the frequency of the current applied to each inductor should be %l, 000&, 1.00.
The order is preferably 0Hz, 500Hz, and LOOOOHz. .

(3) Using the heating pattern wire of each inductor 5, the temperature of the inner surface of the five seams is raised until it becomes non-magnetic, with a penetration time of about 6 seconds after power is turned on, and after applying the appropriate pressure, the heating of the inductor at the final position is 1 Preferably, it is carried out at m 000 Hz. , (4) When an electric resistance welded tube with a wall thickness of 15.9 ms and an outer diameter of 406 mm is heat treated at a speed of I J3 m1 m, s, ooom
Four inductors are installed in a space of
It can be reduced to 20KW.

In summary, the present invention provides an electrical resistance welding line for thick-walled pipes, in which a plurality of inductors are formed to have a predetermined conductor width and are arranged in series at intervals, and a current that exerts a force of 11 on the inductor is provided. The frequency is set to 700-B,00 until the average temperature of the seam at the inlet of the next stage inductor reaches 600-700℃.
01Jz, then the temperature of the seam part is 700-7
The temperature was set to 800 to 700 H2 until the temperature reached 50°C, and thereafter it was set to 700 to 8,000 Hz again, so the present invention maintains the temperature difference between the inner and outer surfaces of the ERW tube seam at a large value. Burnt pure.

It can be simplified and has the effect of reducing power consumption.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention, and FIGS. 2, 3, and 4 are ERW tube axes of inductors in the first, second, and third experimental examples, respectively. FIG. 3 is a diagram showing the relationship between the arrangement position in the direction and the temperature between the outer surface and the inner surface of the welded portion of the electric resistance welded pipe. /...wall thickness, -2...movement direction of the ERW tube, 3. ≠,
S...Inductor, 2...High frequency inverter, 7...
Medium frequency inverter. Procedural amendment (n1 1. Indication of the case Patent Application No. 176785 of 1988 2, Name of the invention Localized continuous heat treatment method for steel pipes 3, Person making the amendment Relationship to the case Applicant (610) Meidensha Co., Ltd. 4, Agent Address: 1-29 Akashi-cho, Chuo-ku, Tokyo, 104 Full text of the specification a Contents of amendment Amend the full text of the specification as shown in the attached sheet. 6; Heat Treatment Method 2, Claims (1) A continuous local heat treatment method for a steel pipe, characterized in that the seam portion is locally sintered and subjected to standard electric resistance welded pipe heat treatment. Treatment method: 600°C to 700°C, medium frequency. is 700°C
Continuous heat treatment method. a Detailed Description of the Invention The present invention relates to a method for local continuous heat treatment of steel pipes. It has already become common to burn, clean, or standardize the ERW tube seam in the ERW tube heat treatment line. In such the above-mentioned line, it is assumed that the electric power of the welding device (not shown) is
Assuming that the welding capacity is approximately 2,000 kW, approximately 2000 kW of power is required to make the sintering or normalizing device have a sintering or normalizing capacity that matches this welding capacity. The problem with this is that the electric power required for the sintering or normalizing device in the line becomes very large. It is particularly important to ensure that the temperature difference between the inner and outer surfaces of the ERW pipe does not become large. For example, it is well known that when a seam portion is heated above a certain temperature, the metallic properties of the surface deteriorate. That is, the 4th part of the sea is 106σC
If the temperature exceeds the limit, the crystal grains of the metal become coarse and the strength decreases. There was also a problem that if the temperature was lower than 950°C, the toughness would not recover. The present invention has been made to solve the above-mentioned problems, and is used in a sintering or normalizing device in an ERW pipe heat treatment line to maintain the temperature difference between the inner and outer surfaces of the seam within a predetermined value. The purpose of the present invention is to provide a method for localized continuous heat treatment of steel pipes that does not cause deterioration of the metal properties of steel pipes and enables power saving. Embodiments of the present invention will be described below with reference to the drawings. 1st
The figure is a curvature view showing the configuration of an embodiment of the present invention. In the figure, an electric resistance welded pipe with a wall thickness of 12 or more is being transported in one direction indicated by the arrow. 31 Hiroshi, 3 is a pure inductor with a length of 400 m to 1500 m for simple use, and these inductors J
, Q, j are arranged in series at predetermined intervals. The arrangement is set so that the time required for a predetermined portion of the electric resistance welded pipe to pass through the inductor barrier (heat penetration time) is 6 seconds or more. The heat penetration time (T) is determined by the following equation. `` > a5 x 10-' x 1; 4, where t is the wall thickness of the tube. In other words, a high frequency current of 700HM to 800011ts is supplied to the inductor 3, and the average temperature of the seam part of the tube l at the entrance of the next stage inductor is 600HM.
Heating is performed from ℃ to 700℃. Next, a medium frequency current of 800 Hz to 700 Hffi is supplied to the inductor DA, and heating is performed until the average temperature of the seam portion of the tube 1 at the entrance of the next stage inductor S becomes 700° C. to 750° C. Next, the inductor S has a frequency of 700H2 to 8000Hz.
The inverters 4 and 7 are set to supply a high frequency current of . Next, by comparing the calculation simulation results and the actual measurement simulation results for the ERW tube seam, we were able to improve the accuracy of the simulation. The results of various calculation simulations are shown in Tables 1 and 2. Table 1 Table 2゜From the above results, it can be seen that inductor conductor 1 [by increasing the frequency of the current applied to 1 inductor per inductor and reducing the number of inductor stands], the total efficiency can be increased and the cost can be increased. There are prospects for a decline in the Based on the above evaluation, the results of experiments were conducted taking into account the arrangement of the inductor. Figures 2 to 4
The figure shows the experimental results. In addition, in FIGS. 2 to 4, experiments were conducted using examples using four and five inductors. Figure 2 shows an outer diameter of 406ss and a wall thickness of 15.911B (7
) In the ERW tube, length 9oomo inductor 3/-3G
13QQl11, arranged in series with an interval of 1250se+1450wk, and each inductor 31 to 341
When the gap between the
@)? Heating current frequency f (H2), inductor conductor width w
(soi) as shown in Table 3, heating time 48
In the case of 8 sec + cooling time 6 sec,
The relationship between the position of the inductor in the axial direction of the ERW tube and the temperature between the outer surface and the inner surface of the ERW tube seam portion is shown. [Margin below y Table 8 Figure 8 is different from Figure 2 in that an additional inductor 3S is provided and the distance between the inductors JIA and 35 is set to L.
Power 1 maintained at 500 m and supplied to inductors 31 to 35
When the frequency and the conductor width of the inductor are selected as shown in Table 4, the relationship between the position of the inductor in the axial direction of the electric resistance welded tube and the temperature between the outer surface and the inner surface of the electric resistance welded part is shown. [Margins below] Table 4 Also, Fig. 4 differs from Fig. 2 in the inductors 31 to 3.
Table 5 shows the two frequencies of power supplied to Hiro and the conductor width of the inductor.
The relationship between the position of the inductor in the axial direction of the electric resistance welded tube and the temperature of the outer and inner surfaces of the electric resistance welded part is shown in the following figure. [Margins below] Table 6 The following has become clear from the first to eighth experimental examples. (1) The heat treatment temperature for the outside and inside of the ERW pipe is 1.00σC.
and 900° C., the power applied to the inductor can be reduced from about 2200 N to about 1620 ff K by changing the width of the conductor of the inductor from 85 mm to 24111 mm. (2) In order to suppress the temperature difference between the inner and outer surfaces of the final heating inductor at the seam immediately after heating to 100°C, the frequency of the current applied to each inductor must be 1,000°C. 1.000 Hz, 500 H1l! , 1,00
The order is preferably 0 HI3. (3) Heating pattern for each inductor After power is turned on, the heat penetration time (passage time through the inductor barrier) is set to about 5 seconds to lower the temperature of the inner surface of the seam until it becomes non-magnetic.
Preferably, heating of the inductor in the final position is performed at LOOOOHz. (4) When an electric resistance welded tube with a wall thickness of 15.9 mm and an outer diameter of 406 mm is heat treated at a speed of 13 m/m, four inductors are installed in a space of 8 ρ00 mB, and the power supplied to these inductors is The power consumption can be reduced from the conventional approximately 2000KW to 162KW. Note that the number of inductors arranged in the seam portion is not limited to three. In summary, in the axial direction line of the electric resistance welded pipe of the present invention, a plurality of inductors are formed in a predetermined conductor width and are arranged in series at intervals, and the frequency of the current applied to the inductors is TOO~8000℃ until the average temperature of the seam at the inlet of the next stage inductor reaches 600~700℃.
Hz, then i of the seam at the inlet of the next stage inductor at i! 800 until llt reaches 700-750°C
~700Hg, then again 700~8000
Hz, so the temperature difference between the inner and outer surfaces of the ERW tube seam section was kept at a small value and the sintering was carried out.
It is possible to standardize and also has the effect of reducing power consumption. Brief explanation of the raw drawings Figure 1 is a perspective view showing the actual production, and Figure IK2, Figure 8, and Figure #I4 are the first experimental example, the second experimental example, and the eighth experimental example.
FIG. 7 is a diagram showing the relationship between the arrangement position of the inductor in the axial direction of the electric resistance welded tube and the temperature between the outer surface and the inner surface of the welded portion of the electric resistance welded tube in an experimental example. /... ERW pipe, 2... Movement direction of the ERW pipe, 3. Da. S...Inductor, 6...High frequency inverter, 7...
Medium frequency inverter. Corrected as "annealing". (7) "600°C to 700°C" stated in the 4th line of page 5 of the same Ministry is corrected to "600°C to 700°C." (8) [700″C to 7 stated in the 7th line of the same page of the same book]
50 J is corrected to "700°C to 760". (9) “(Company) 2200” listed in Table 4 on page 9 of the circular
Correct J to 2,200-J (total). αQ 2,000-J
J is corrected to 2,000 J (total). (2) "Where" written on the 14th line of the same page of the same book is amended to read "or in four places." (To) "Hardened pure" described on page 12 of the same book is corrected to "annealed". [Attachment] (1) In an electric resistance welded tube heat treatment line where the seam is locally annealed and simplified, a plurality of inductors are placed at the seam, the seam is heated to a predetermined temperature, and the seam is supplied to the inductors. 1. A method for localized continuous heat treatment of steel pipes, characterized in that the frequencies for heating are set in the order of high frequency, medium frequency and high frequency along the transport direction of the ERW pipe. (2) The method for local continuous heat treatment of steel pipes according to claim 1, characterized in that the high frequency is set from 700 Hg to 8000 Hz, and the medium frequency is set from 800 Hz to 700 Hz. 2. The method for localized continuous heat treatment of a steel pipe according to item 1, wherein the average temperature of the seam portion at the mouth is in the range of 700'0 to 700'0. (4) The conductor width of the inductor is from 24116 to 85111
A method for localized continuous heat treatment of a steel pipe according to claim 1 set forth in claim 1. Procedural amendment form (method) % formula % 2. Name of the invention Steel pipe local continuous heat treatment method 3. Person making the amendment Relationship to the case Applicant (610) Meidensha Co., Ltd. 4, Agent address: 104 Akira, Chuo-ku, Tokyo Ikocho 1-29-J Jusaikai Building Telephone 0
3 (545) 2251 (Representative) Subject of January-February 18, 1980 amendments Column for the content of amendments to the procedural amendment submitted on November 8, 1980. 7. Contents of the amendment (1) r stated in page 8, lines 14 to 15 of the procedural amendment submitted on November 8, 1980 (/3) As stated in page 12 of the same document... to correct. "tr(/J)
"Annealed pure Jt-r" described in page 12, line 10 of the same book
and correct it. ” and calmly corrected 0 or more

Claims (1)

[Claims] In an electric resistance welding pipe welding line for locally sintering and standardizing a seam part, a plurality of inductors are arranged in series at a predetermined interval at the seam part, and each of these inductors is The conductor width of is formed to a predetermined value, and the frequency supplied to these inductors is set from 700 IIL5 to 8000 *w until the average temperature of the seam part in the first stage induction population reaches from 600°C to 700°C, Next. The average temperature of the seam part in the 2nd stage induction 1,000 population is 70
From 800 Hz to 700 from 0℃ to 750℃
Hz, and then set the inductor frequency to 700-8000 again.
1. A method for localized continuous heat treatment of steel pipes, characterized by setting the temperature so that Hm.