JPS6024322A - Heat treatment of large-diameter steel bar over entire section thereof and heat treating device with continuous movement - Google Patents

Abstract

PURPOSE:To perform simultaneously heat treatment of a hot-rolled steel bar over the entire section thereof and formation of the effective layer in a thick surface layer part by subjecting the steel bar to an induction heating treatment then cooling the circumferential surface at both ends thereof, passing the steel bar through two stages of liquid cooling jackets and cooling the bar. CONSTITUTION:A large-diameter steel bar W is passed through an induction heating mechanism 1 where the bar is preheated with a coil C1 part and is normally heated with a coil C2 part. Air or mist is injected from a jacket MJ in a soaking zone 2 to decrease primarily the temp. on the surface layer in the prescribed range at both ends of the bar W. The steel bar is thereafter successively hardened to the prescribed depth and is quickly cooled in a jacket QJ1 under injection of a cooling liquid and is quickly cooled in the jacket QJ2 of a post stage in a cooling mechanism 3. The steel bar W is heat-treated by the above-mentioned method in such a way that a martensite structure is formed in the surface layer extending to the thickness corresponding to 10-25% of the diameter thereof and that a martensite or 50% martensite structure is formed to the remaining part reaching the central part.

Description

[Detailed description of the invention] and continuous movement heat treatment equipment.

For example, in rollers for roller conveyors, sliding shafts, tension rods for building rods for mills, etc., the surface should have as much wear resistance as possible, and the center should have the desired mechanical properties. There is a lot of demand for shafts like this. Except for cases in which special @ is used for such bars, conventionally, hot-rolled steel bars made of low-alloy steel are heated in an electric furnace or combustion furnace to a predetermined quenching temperature uniform throughout the entire cross section, and then heated with oil. The conventional method described above involves two heat treatment steps to obtain the desired quality by performing a heat treatment step consisting of a heat treatment step of hardening and tempering, and a surface hardening and tempering step of hardening to a predetermined depth. Of course, the furnace type requires a long time for heating during refining, and when the material to be treated has a large diameter, for example, 90 to 100 ranφ or more, cooling of the center part is extremely slow in oil quenching after heating. As a result, the tempered young fruit tends to become thinner, and the structure becomes coarser, which causes a decrease in toughness.

On the other hand, in the case of rapidly cooling and quenching a material by heating it with an induction heating means, for example, even if a power source with an output of 600 kW, which is one of the highest in the current induction heating power source, is used, it is difficult to heat the steel material. The thickness of the effective hardened layer from the surface is limited to about 15 bags even if a coolant with high cooling ability (water or Solipul) is used, and if deeply hardened as described above, the bar material will be hardened. It is believed that the occurrence of burnt ends later is unavoidable, so in anticipation of this, a bar material that is sufficiently long than the required length is hardened, and then the burnt ends are cut off. Ta.

As mentioned above, the purpose of the invention was to solve all the problems that conventionally existed when heat treating the entire cross section of a large diameter copper rod and forming an effective hardening layer as deep as possible on the surface layer. and at least 60°, for example 90° to
By applying a single heat treatment process to hot-rolled steel # made of low-alloy steel with a large diameter metal of over 100 mm, eliminating the conditioning process, it is possible to achieve a total heat treatment effect that exceeds that of conventional heat treatment. A new large-diameter steel that enables cross-sectional heat treatment and the formation of a thicker effective layer on the surface at the same time, without causing any burning at the edges, and with low distortion. The present invention provides a method for heat treatment of the entire cross section of a bar and a single continuous movement heat treatment.

The invention will be described in detail with reference to an embodiment of the apparatus shown in FIGS. 1 to 4(b).

FIG. 1 shows the whole view of a continuous movement heat treatment apparatus for a large diameter steel bar in its entire cross section according to the invention, and the steel bar W is fed in the axial direction along the entire feeding path shown by the arrow L. FIG. Follow the feeding path above in order of feeding direction! A heating mechanism 1, an air or mist jacket MJ (hereinafter referred to as jacket MJ), and a cooling mechanism 3 are provided. The above induction heating mechanism 1
For example, it is made up of induction heating coils C8 and C2 which are connected in parallel to an output power source E with a predetermined frequency and are spaced apart from each other by a predetermined interval S. The above-mentioned jacket MJ is provided between the above-mentioned induction heating mechanism 1 and cooling mechanism 3, and has a soaking zone 2 consisting of a predetermined interval S2 determined by the above-mentioned power source E, steel rod diameter, heating temperature, feeding speed, and other specifications. For example, the electromagnetic pulp B
Air or mist supplied by a hose h1 connected to an air or mist supply source P1 via a hose h1 can be injected from the inner ring wall in the axial direction. The cooling mechanism 3 consists of liquid cooling jackets (QJ) and QJ2 (hereinafter referred to as "jackets QJ" and "QJ2") each consisting of an annular tube whose axis is the feed passageway, and both of which are made of water or a water-soluble polymer. Bose h connected to a cooling liquid source P2, such as an additive solution, Solipul. It is possible to inject predetermined flow rates of cooling liquid supplied by and h2 from the inner ring wall,
Only the hose 1]2 connected to the jacket QJ2 is arranged so as to be connected to the cooling liquid supply source P2, for example, via a solenoid valve B2. 4 is a detection mechanism that detects the end of the steel rod placed at a predetermined position along the feed path.
For example, a beam sensor, an air sensor, a limit switch, etc. may be used as long as it can detect the arrival of the forward end or rear end in the feeding direction of the steel rod W being sent around the feeding path and output a detection signal sf. The detection signal S output by the mechanism I is set to be input to the first timer T1 and the second timer T2.

First timer T1Vi e.g. T1-a and T, l)
There are two timers, the former being the above-mentioned detection 1t.
1 at a predetermined elapsed time from the input of the detection signal S, and the latter at a predetermined time elapsed from 11 o'clock mentioned above, which is determined by the interval from Wi4 to Jakela) MJ and the feed rate of the steel rod W.
The electromagnetic pulp B+ k
The outputs OI and C5 to be opened are sent to the electromagnetic pulp B1, and the second timer T2 is also set to T2C and T2.
, d, the former is also determined by the distance from the detection mechanism 4 to the jacket QJ2 and the feeding speed of the copper rod W, and the timer is set from the time of input of the detection signal 5 to the top i.
, it 12 at a predetermined elapsed time when the elapsed time is longer than at tl+α
At t2+β when the electromagnetic pulp B2 is turned on from 12 o'clock to the predetermined time t2+β, the output c2> and the output 0.0. ea The electromagnetic pulp B
Therefore, if all the specifications in the above configuration are set as specified, the local area near the end face from each peripheral end face toward the center of the steel frame W as shown in FIG. In the case where the predetermined range A is, for example, single unit feeding in the feeding process, the tip end area (Jakera started by the output signal S) is from time t1+7α to t in the air or mist injection continuation time period from MJ.
The fluorescent end side receives the injection from the time t at the air or mist injection duration g from the jacket MJ, which is started by the rear end face detection signal S, from the time t to the time 117α. For example, in the case of continuous feeding, the jacket l-MJ is started only by the tip end face detection signal S.

During the air or mist injection duration period, the predetermined range A on the rear end side of the leading copper rod W and the predetermined range A on the tip side of the trailing copper rod W are continuously injected with air or mist. It can be set as you want. In addition, by the same principle as above, as shown in FIG. 2, a local predetermined range B near the end face from each circumferential end face toward the center of the steel rod W is a predetermined range from the time when the end face detection signal S is input during the feeding process. Time has passed 12
The values of the predetermined ranges A and B near the end face of the jacket QJ2 can be set so that the cooling liquid passes through the jacket QJ2 during the cooling/injection stop duration period of the jacket QJ2 that stops the cooling liquid injection from time to time t2+β. This will be explained later. Reference numerals 51 and 51' denote steel rod restraining roller groups formed in multiple pairs in the left and right and up and down directions, which are provided along the feeding path of the steel rod W in front of the induction heating mechanism 1 and behind the cooling mechanism 3, respectively. The rollers of one of the two rollers are driven by a drive source (not shown) to move the rollers in the direction of the arrow on the feed path, and the other rollers are driven by a free-form roller. . Also, 'JJ44' J restraining roller groups 52 are provided along the feeding path of the soaking zone 2 and are paired in the vertical and horizontal directions.
The rollers 51, 51'2 and 52 each have a rotationally freely rotating structure, and each of the steel rod restraining roller groups 51, 51'2 and 52 are used to feed the steel rod in accordance with the predetermined outer diameter of the steel frame W. It contacts the outer periphery of W and can regulate the copper rod from the top and bottom and left and right directions. 53.5
3 is a drive roller for carrying in steel rods, and 54 is a roller for carrying out steel rods.

One large-diameter tray frame W carried into the continuous moving heat treatment apparatus having the above configuration and fed along the feed path has at least 6() diameter diameter.
The above is made of low-alloy steel that has not yet been formed by hot rolling. As shown in part (b), the end face is chamfered or rounded to a degree of 10C or IOR or more prior to delivery.

1 and 4 (70-chard shown as al and Wj4 ft. )) The horizontal axis represents the elapsed time t (min), and the vertical axis represents the temperature °C. zonn
The description will be made according to a temperature characteristic curve diagram represented by a solid line curve X, a dashed line curve Y, and a broken line curve 2.

First, turn on the Nf5 conductive thermoelectric E, and then turn on the induction heating coil C.
Start energizing 8 and C2, and connect to the air or mist supply port 1], which is connected to the air or mist supply valve Pl. The solenoid valve B inserted into the hose connected to the coolant supply source P2 remains closed.
, are maintained in the open state, and each supply source P
1 ・P2 is driven. In this state, the steel rod is transported to the W purple equipment. , Sake@bar W is the drive roller 5 for carrying in the steel bar.
According to 3.53, the feed is carried out in the axial direction according to the upward arrow on the feed path while maintaining a predetermined speed, until the tip of the feed slows down to the detection mechanism 4. The detection mechanism 4 detects the tip of the arriving steel rod W and outputs a detection signal si to the first timer T and the second timer T2.

Steel #W, which continues to move forward, passes between @pay restraint rollers #51 and enters into the induction heating mechanism 1 sequentially from the tip. The induction heating (structure 1 consists of induction heating coils C8 and C2 connected to a predetermined frequency/output power source E as described above, and both are arranged apart from each other at a predetermined interval S+', so that the steel rod wt- While sequentially passing from the inlet side to the outlet side of the induction heating mechanism 1, the surface temperature at the outlet side of the induction heating coil C1 is approximately 870°C, and the center temperature is approximately 100°C to 100°C.
While the surface temperature of the steel rod W decreases due to heat conduction toward the center while it is preheated to about 56° C. and then reaches the induction heating coil C2 which is passed through a predetermined interval S, the temperature at the center decreases. further rises, and the subsequent induction heating coils C, VC cause main heating? When it reaches the outlet side of the induction heating coil C2, the surface temperature is approximately 920°C and the center temperature is 6.
The temperature is raised to about 00 to 650°C. However, only the periphery of the end face of the steel rod W is determined by the power supply frequency used or the induction heating coil C, -
Although there are some differences Fi depending on the gap between C2 and the circumference of the steel rod and other factors, the temperature is slightly higher than that on the surface due to the gill effect, which is a characteristic of induction heating.

The steel rod W that has passed through the induction heating mechanism 1 advances through the soaking zone 2 in the direction of the cooling @ structure 3. In the soaking zone 2, there is a jacket near the outlet side of the induction heating PAJ and 1).
MJ is placed and the corresponding jacket) MJ is placed as described above.
Since the design is such that air or mist is injected from time tt to +9 o'clock t, the tip of the steel rod W exiting the induction heating mechanism 1 is immediately injected with air or mist starting at 18 o'clock at MJ. Entering the jet stream of the hamster and receiving air or mist jet while moving from the tip surface to a predetermined range A,
The temperature of the surface layer, which is hotter than the center portion, can be temporarily lowered rapidly. However, the predetermined range A(i
-The central portion υ except for this moves through the jacket MJ in which the injection of air or mist is stopped at time t1+α. Since the heat equalization zone 2 is set at a predetermined interval S2, the surface temperature of the steel rod W decreases to about 760°C by the time it reaches the cooling mechanism 3, and the center temperature rises to about 730 to 750°C. A predetermined area A that is heated and is sprayed with the air or mist.
The temperature has also risen to around 760 degrees Celsius.

The steel rod W passing through the cooling mechanism 3 is rapidly cooled by the JAKERA (QJI) which is injecting a predetermined flow rate of cooling liquid, and the steel rod W passes through the cooling mechanism 3.
The surface layer with a thickness corresponding to 10 to 25% of the diameter of the 10-25% of the surface becomes hardened by the rapid cooling, and then reaches the quenching temperature of Jacquera) QJ2 [-, and is further quenched by a predetermined flow rate of the cooling liquid, for example, the above-mentioned Jacquera) QJ+. 50
The surface, which has fallen to around 650°C, is further rapidly cooled, and this rapid cooling removes the return heat from the center, which moves toward the surface by heat conduction due to the temperature gradient with the center, which is still at a temperature of around 650°C. Facilitate. However, the above jacket QJ
As mentioned above, the rapid cooling at t is not applied to the steel rod part 1' since the injection of the cooling liquid from the JA2 is stopped until t2 + β as described above. Therefore, the heat at the center of the predetermined range B is conducted in the axial direction and the circumferential direction, and the circumferential UMI of the end surface is ~150°C.
The temperature rises to a certain extent, and the residual heat is dissipated to the target. In this way, the temperature of the surface layer part other than the surface layer in the predetermined range B is reduced to at least 7 ( ) to 80
While maintaining the temperature at 150°C, the temperature at the center is rapidly lowered to about 150°C. After undergoing the above thermal process, the total length of the steel bar W is sequentially divided into the induction heating mechanism 1, the soaking zone 2, and the cooling mechanism 3.
10 of the diameter of the steel rod W while passing through the heat treatment equipment consisting of
The surface layer having a thickness corresponding to ~25% is heat-treated to form a martenzite structure, and the remaining portion down to the center is heat-treated to form a martenzite or VC structure of approximately 50% Fi martensite.

During the process of passing the steel 41W through the heat treatment chamber, the steel rods W in the heating zone and the cooling zone are connected to steel rod restraining loans #51 and 52, which are arranged in pairs in the vertical and horizontal directions outside the respective zones. And, thermal strain and cooling strain due to restraint are regulated by 52 and 51'.

The steel frame W may be carried individually into the heat treatment equipment,
Also, continuous VC4%> may be entered.

In the case of the above-mentioned continuous carrying-in, the rear end surface of the preceding steel rod W and the distal end surface of the following steel rod W may collide with each other as shown in FIG. 1'. The following interval feed p is used.

That is, as shown in Fig. 4 (C1), a spacing is provided between the rear end surface of the leading copper rod W1 and the front end surface of the trailing steel rod W2. From jacket QJ.

The length of the copper rod W equal to the distance to the inlet side of the steel rod and the temperature of the steel rod W when it reaches the inlet side of the Jacquera QJII are set to be approximately the same as the thermal expansion of the steel rod. In this case, the air or mist injection duration α is the above interval I
It goes without saying that the θr fixed ranges A1 and A2 of the copper rods W, $-, and W2, which move back and forth depending on the copper feeding speed including i, must be set so that they receive air or mist injection. By doing so, the air or mist jet not only impinges not only on the circumferential surface of the steel rod W in the predetermined range A but also on the end surface, and not only temporarily lowers the temperature, but also
Thermal expansion of the copper rod W in the axial direction is not restricted by the trailing steel rod, and can be freely extended.

A predetermined range A of the end of the steel bar that is sprayed with air or mist when passing through the heat treatment equipment and a predetermined range B of the end of the steel bar that is not sprayed with coolant again are determined by the hardenability of the steel bar material. It is determined by the test heat treatment performed in advance according to the diameter, temperature IW, and degree of chamfering, but from various test data, the feed rate? The fixed predetermined range A of the lifting table is such that the steel bar is small for small diameters and large for large diameters, for example, 75f117+1φ.
It is preferable to set 70 wR, 9 degrees, and 90 mm φ to about 100 circles, and the predetermined range B to be about 2 to 2.5 times the above predetermined range A.

The feeding speed of the steel rod W that can be heat-treated by the above-mentioned heat treatment equipment varies depending on the power output, the diameter of the crushed steel, and other factors, and it goes without saying that the speed will be high for large output and small diameter, and slow for small output and large diameter. Since induction heating is rapid heating, the heat treatment time, that is, the time for moving from the inlet side of the induction heating coil C to the outlet side of the jacket Q J 2 is about 4 to 8 minutes.

As described above, the steel rod WFi, which has been heat-treated over its entire cross section while moving through the heat treatment equipment, is discharged from above the discharging roller 54 and heated to a temperature of 180 to 25, for example, in the electric furnace in the next step.
A tempering treatment is performed at 0° C. for 4 to 5 hours to complete the entire heat treatment process.

Some of the many examples carried out by the present inventor on copper rods of various diameters are shown below.Example (1) Specimen: Hot-rolled steel of manganese steel phase drawing material for machine structures Rod diameter: 90mm Length: 7,000m1+1 Surface J4y, 912C (2) Heat treatment; Mobile heat treatment equipment power supply; 150 KW -I KH2 Induction heating coil; 2 coils connected in parallel Air injection pressure: 3kgf/ffl Air injection range A; 100mm Liquid cooling jacket; 2 coolant flow rate; each 1501/min Coolant injection stop range B; 200 mm heat treatment area: L130rnX Steel bar feed rate; 150 mm/n-+in electric furnace tempering;
200℃X 5 hr (3) Heat-treated product a Exterior inspection: No edge warping at all, same axial bending; 0.7 corners/m Therefore, the tolerance 3 flaws/ It has been confirmed that it is not only far below mk, but also has the effect of straightening the curved wrinkles of the steel bar during heat treatment.

b. Accuracy test a. Central part hard awn measurement; cross-sectional hardness 1i111 The hardness obtained by plotting the results on the coordinates where the horizontal axis is the distance F'lif mm from the center and the vertical axis is the hard awn HV and HRC. The characteristic curve is shown in FIG. 5(a).

Mouth edge hardness measurement; vertical section hardness measurement ay (1okg
) is shown in Figure 5 (1)), which is filled in for each measurement position.

However, the measurement position close to the surface (is the surface Yoshi Q, I'm at 51Rm.

As shown in FIGS. 5(a) and 5(bl), the entire cross section of the steel bar is heat treated to the center and approximately 1 to 1 deep from the surface.
Vickers hardness HV 600 or more, depth 13~15rrrm H
V500 or higher, HV 400 up to depth-g23~25fi
The thickness of the effective hardened layer is approximately 2 times the diameter.
5%, and it has been confirmed that it is extremely thick, with a depth of approximately 25mm.
From 4411J to the center, a relatively soft and tempered phase layer of about HV380 or higher is formed.
-1, and the hardness near the ends also shows almost the same hardness as the center at each depth from the circumferential direction. It clearly shows that the entire cross-section heat treatment effect is achieved.

Microscopic observation of crystal grain dust: Fig. 6(a) shows a micrograph (xloo) of crystal grains in the surface layer. The grain size was 8.

Mouth structure; Fig. 6 (bi and (C1) show tissue micrographs (X400) of the surface layer and central part. Fig. 6 (b) shows fine martensite, and Fig. 6 (C) shows martensite. and 50%
A mixed martensite tissue was observed.

From the micrographs shown in Figure 6 (al, '(bl) and (C1), it is clear that the fi hot-rolled large-diameter copper rod of the present invention can be heat-treated only once, resulting in extremely thick quenching on the surface layer and on the neck. It was confirmed that the remaining portion at the center 1 could be subjected to a heat treatment higher than that of Fi heat refining.

In the above embodiment, the induction heating coil "1" and "C2k" are used as the induction heating mechanism. The number of coils may be 3, and the number of liquid cooling jackets is not limited to 2.
In the case of a large diameter, there may be three jackets, and if necessary, the second jacket and the third jacket may be used to stop the injection of the cooling liquid to a predetermined area B near the end. .

A plurality of power sources may be used for the power source E connected to the induction heating mechanism 1, and the frequency used is such that the entire cross section of the steel bar is almost as quickly as possible before reaching the cooling mechanism 3. It is only necessary to select a frequency that provides a uniform temperature, and it is within the scope of the present invention even if the frequencies of the n power supplies are different.

For example, even when there is a small diameter shaft part at the end of a large diameter shaft part as shown in FIG. The same effect can be obtained by rounding or rounding the chamfer.

Furthermore, in the above-described embodiment, the detection mechanism is installed at the installation position 'fr: in front of the steel rod restraining roller group 51, but at least the detection signal can be used to stop the injection of the air mist and the injection of the coolant to the predetermined ranges A and B. The number of detection mechanisms is not limited to one, but may be two, or if there are two jackets for stopping the coolant injection, the number of detection mechanisms may be three.

When there are two jackets for stopping injection of the coolant, it is more effective to make the predetermined ranges B and B' different.

In the above embodiment, tempering is carried out in a furnace, but a continuous induction heating quenching and tempering line may be constructed by adding a continuous heating and tempering device to the continuous moving heat treatment device #f. .

The operation of the present invention and the effects brought about by it are as follows. 1 (1) Hot-rolled copper made of low-alloy steel with a large diameter of at least 60 threshold φ or more and exceeding 100 mm is directly heat-treated in its entire cross section without going through a hot-rolled copper blast tempering process.
The surface layer VC, which has a thickness corresponding to 10 to 25% of the diameter of the steel bar, is an effective hardening layer, and the remaining part up to the center is heat treated to a degree higher than that obtained in the step N of step X. It makes it possible to be effective.

(2) The above heat treatment is performed by rapid heating and rapid cooling using Fi induction heating, so the structure is fine not only in the surface layer but also in the center, and due to the extremely thick hardened layer on the surface,
Not only are the defects noticeable, but the central area is also
It is rich in W-ness.

(3) The end face of the steel bar is fully chamfered or rounded to IOC or 1 (IR) in advance and then heat treated, and during the soaking process, air or mist is fully injected into a predetermined range of the high temperature end. It suppresses overheating of the relevant part and uniformly heats the whole length and entire cross section by 20%. During the cooling process, the rapid cooling is interrupted in a predetermined range at the end where the cooling effect is high, so that the residual heat is retained in the relevant part and overcooling is suppressed. Since the cooling rate is set to be approximately the same over the entire length, the heat treatment effect over the entire cross section can be made uniform over the entire length, and the edge burning phenomenon that was conventionally considered unavoidable is completely eliminated. becomes possible.

(4) The steel rod is completely restrained by a group of steel rod restraint rollers from the top and bottom and from the left and right (this is a local heat treatment that heats and cools one by one, so there is no large distortion that occurs in the conventional thermal refining process that heats the entire body). It does not occur, therefore, it is not necessary for subsequent straightening, and the strain is extremely low enough to straighten the bending of the raw steel rod.In particular, by performing heat treatment at predetermined intervals in continuous movement heat treatment. Compared to the case where the front and rear copper rods are fed while their end surfaces are in contact with each other, the elongation due to thermal expansion of the leading steel rod causes the trailing steel rod to slip on the feeding path, causing air or mist injection or cooling liquid injection to stop. This may disrupt the timing of the following copper rod, or may cause circumferential bending of the leading steel rod due to the restrictions imposed by the trailing copper rod. .

As mentioned above, the present invention is an epoch-making product that brings remarkable effects both from the economical and quality standpoints, and its practicality is outstanding.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view showing the entire arrangement of an embodiment of the present invention, and FIG. 2 is a front view showing a predetermined range A for air or mist injection and a predetermined range B for stopping coolant injection. figure,
3(a) and 3(b) are front views showing chamfering or rounding applied to a large diameter steel bar to be heat treated according to the present invention, FIG. 4 (al is a flowchart showing the heat treatment process of the present invention, FIG. 4(b) is a temperature characteristic curve diagram of the steel bar during the heat treatment process performed by the embodiment apparatus shown in FIG.
Figure (C1 is a front view illustrating the feeding method of the steel rod in continuous movement heat treatment, Figures 5 (a) and (b) are the hardness distribution characteristic curve of one side and the end of the steel rod according to the present invention, respectively. Near half-longitudinal hardness measurement diagram, @61'x+ (a), (b)
and (c) are micrographs showing the crystal grains, surface layer structure, and center structure of a steel bar according to an example of the present invention, respectively, and FIG. 7 is a front view showing another shape of the @ bar for carrying out the present invention. 1... Induction heating mechanism 3... Cooling mechanism 4... Detection mechanism 51.51', 52... Restriction roller group W, W
l, W2... Steel bar C,, C2... Induction heating coil MJ... Air or mist jacket QJ, ,
QJ2...liquid cooling jacket)s...detection signal T2
...Timer B1, B2...Pulp C...Chamfer R...Ku-Mizuke! 1, 1, 1+, ]) person, fX, Shuha Netsushin Co., Ltd., 1゛f1, Uto, Patent Attorney, Kobayashi, 11.1j No. 2
Figure Section 3 Figure (b) Figure 4 (0) Procedural amendment (method) August 17, 1980 Director General of the Patent Office 1. Indication of case 1989 Patent Application No. 26333 2. Name of invention Large diameter Method for heat treatment of entire cross section of steel rod and continuous moving heat treatment equipment 3, relationship with the case of the person making the amendment Patent applicant 4, agent ◎105 Address 2-2-20-6 Nishi-Shinbashi, Minato-ku, Tokyo, subject of amendment 7. Contents of the amendment In the title of the invention in the description, "Method for heat treatment of entire cross section of large diameter steel rod and continuous movement heat treatment method" is corrected to "Method for heat treatment of entire cross section of large diameter steel rod and continuous movement heat treatment apparatus" do.

Claims (1)

[Claims] 1) A hot-rolled steel bar made of low-alloy steel having a large diameter of at least 60 squares is chamfered or rounded to a predetermined dimension on both end faces of the steel bar, and then While the relative movement causes the passage through a plurality of induction heating coils, preheating by one or more induction heating coils in the previous stage and main heating by the latter induction heating coil are sequentially performed, and the main heating By applying forced manual cooling or forced mist cooling only to a predetermined area around the circumference of both ends of the steel rod, we prevent excessive heat accumulation in the area, and cool each part of the steel rod by the end of the specified 9 hours of feeding. The entire portion from the light surface to a predetermined quenching temperature is heated up to a predetermined quenching temperature, and the remaining portion up to the center is heated to a temperature close to the above quenching temperature. During the passage, the cooling liquid sprayed from the liquid-cooling jacket in the previous stage sequentially quenches and rapidly cools the surface of each part of the steel rod to a predetermined depth in the reeds, and from the single or multiple liquid-cooling jackets in the latter stage, it cools down the surface of each part of the steel rod in the same manner near both ends. Cooling liquid is sequentially injected onto the other circumferential surfaces except for a predetermined area, so that residual heat is retained near both end surfaces, while heat is transferred from the center of the steel rod toward the second surface on the other surfaces. By applying Σ rapid cooling to promote heat absorption, a martensite structure is formed in the surface layer with a thickness equivalent to 10 to 25% of the steel rod diameter, and martensite structure is formed in the remaining part up to the center. A method for heat treatment of the entire cross section of a large-diameter steel bar, which is characterized by sequentially forming a structure of about % martensite over the entire length of the steel bar, and then subjecting the steel bar to a tempering treatment for a predetermined period of time. A hot-rolled steel bar made of low-alloy steel having a diameter is chamfered or rounded to a predetermined dimension on both end faces of the steel bar, and then the rear end face of the steel bar that precedes and follows the feeding path. The steel bar is fed in the axial direction so that a predetermined gap is left between the front end surface of the steel bar and the v
While passing through the induction heating coils of jt number, preheating by a single induction heating coil or a plurality of TFI induction heating coils and main heating by a subsequent induction heating coil are sequentially performed. By applying strong mlJ!cold cooling to only the steel rod end faces and the layers near both end faces in a predetermined range, excessive heat is accumulated in the relevant parts.
While preventing the steel rod from reaching a predetermined depth from the surface of each part of the steel bar by the time the predetermined feeding time has elapsed? f - to a given quenching temperature;
In addition, the temperature of the remaining portion up to the center is sequentially raised to a temperature close to the above-mentioned quenching temperature, and while the cooling liquid is passed through multiple liquid cooling jackets in the subsequent feeding process, the cooling liquid is injected once from the previous liquid cooling jacket. The surface of each part of the steel bar is sequentially quenched and rapidly cooled to a predetermined depth, and cooling liquid is sequentially injected from one or more liquid cooling jackets at the subsequent stage to both end faces and other surfaces except for a localized area in the vicinity. Then, while retaining residual heat in the vicinity of the side end surface, rapid cooling is sequentially applied to the other peripheral surfaces to promote absorption of return heat that conducts heat from the center direction to the surface direction of the steel rod. A martensite structure is formed in the surface layer with a thickness equivalent to 10 to 25% of the diameter, and a structure of martensite or about 50% martensite is formed in the remaining part up to the center f: Formed sequentially over the entire length of the steel bale After that, the steel bar is subjected to a tempering treatment for a predetermined period of time. 3) Chamfering or rounding on both end faces of the steel bar is JO
The method for heat treatment of the entire cross section of a large-diameter steel bar according to claims 1 and 2, wherein 'C' is greater than or equal to IOR. 4) The distance between the rear end surface of the leading steel rod and the front end surface of the trailing steel rod that is fed in the axial direction through the feeding passage is the same as that between the inlet side end surface of the foremost induction heating coil in the plurality of induction heating coils and the first liquid Claim 2, characterized in that the length of the steel rod corresponding to the distance between the end face on the inlet side of the cold jacket and the thermal expansion determined by the temperature rise of the copper rod are set to be almost the same. A heat treatment method for the entire cross section of a large diameter steel bar. 5) A regular-sized steel bar with a large diameter of at least 60 mm and which is chamfered or rounded to a specified size on both end faces.
an induction heating mechanism consisting of two or more heating coils that are sequentially provided along the nine axially feeding paths at a predetermined speed;
A cooling mechanism comprising an air or mist jacket adjacent to the outlet side of the induction heating mechanism and two or more liquid cooling jackets separated from the air or mist jacket by a predetermined distance, and a steel rod provided at a predetermined position in the feed passage. The above-mentioned detection mechanism includes a detection mechanism that detects an end, and a group of restraining rollers that are arranged at a predetermined position along a feeding path and can contact the circumferential surface of a passing steel rod from above and below and from left and right. A detection signal is output by detecting the entire tip of the incoming steel rod in the feeding direction, and the air or mist supply valve to the air or mist jacket is opened only during a predetermined period of time via the mamer, and the cooling (in some cases) A large-diameter steel rod with a full cross section, characterized in that the cooling liquid supply pulp to one or more liquid cooling jackets other than the frontmost liquid cooling jacket i of A is configured to be closed only during a predetermined time period. continuous moving heat treatment equipment.