JPS5989712A - Heat treatment of steel by high density energy - Google Patents

Abstract

PURPOSE:To perform efficient heat treatment on the surface of steel by irradiating a laser beam to the surface of the steel to melt the surface and heating the surface to be treated by using the other heat source before or after the irradiation. CONSTITUTION:A tubular work R, such as a rolling roll or the like, which is kept rotated around a revolving shaft RL, is preheated in the position to be heat-treated, at the heat energy smaller than the heat energy of the succeeding laser working, by the arc AC1 generated from a TIG torch T1 for preheating under the supply of inert gas G1 from a gas supply nozzle N1. The position to be heat-treated is then melted by a laser beam LB irradiated via a condenser lens 4 while the inert gas NG introduced through the supply port 2 for nozzle gas of a laser working head 1 is ejected from a hozzle hole 3. The steel is maintained at a prescribed temp. or above without being melted by the arc AC2 generated from a TIG torch T2 for after heat treatment to perform the after heat treatment of the position to be heat-treated, whereby the heat-treated part LP is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for highly efficient heat treatment of steel surfaces by using a laser beam in combination with other heat sources.

As is well known, the energy density of a laser beam is extremely high, and can easily be increased to more than 100,000 times that of arc welding. For example, the energy density W/Cm2 of an oxyacetylene flame is about 103, and the energy density W/Cm2 of an argon arc (20
The energy density of 0A) is about 1.5 x to 4, whereas the energy density of a continuous laser beam is 10g and that of a pulsed laser is as high as 1013. Therefore, the use of such a high-energy-density laser beam facilitates processing such as surface hardening, welding and cutting of steel materials, and has been used in various fields in the past. Although laser beams are thus very useful, they are not necessarily without problems. That is, the efficiency of melting steel by a laser beam is: (1) proportional to the square of the laser power, (2) proportional to the fourth power of the beam diameter, and (2) proportional to the square of the energy absorption rate.

Of these, ■ and ■ are determined by the laser oscillator, but ■ is greatly influenced by the irradiation technique. Therefore, it is necessary to increase the energy absorption rate on the steel surface, and for this purpose, 1) utilizing the multiple reflection effect due to surface roughness, 2) improving wavelength absorption with an oxide film, 3) using laser plasma, etc. Measures such as indirectly increasing energy efficiency using secondary effects are necessary.

The present invention was invented in response to these circumstances, and is intended to efficiently heat treat the surface of steel. That is, the present invention provides a steel heat treatment method in which the surface of the steel is irradiated with a laser beam to melt the surface and modify the surface properties. Heating is performed using a heat source such as TIG arc high-frequency heating, direct energization, a gas burner, or a laser beam from a device other than the above-mentioned laser group/device, and at this time, the heating by the heat source is less than or equal to the thermal energy of the laser beam. That is.

The present invention will be described in detail below with reference to the drawings.

Fig. 1 is an explanatory diagram showing the laser beam irradiation method, where ■ is a laser processing head, 4 is a condensing lens provided inside the head, and is arranged so that the laser beam LII is focused on the surface Rs of the workpiece R. It is.

3 is a nozzle hole through which the laser beam LB passes.

On the other hand, the laser processing head 1 is provided with a nozzle gas supply port 2.
is supplied into the laser processing head 1, and the laser beam L
This prevents the evaporated matter generated from the melting region (keyhole) caused by B from adhering to the condenser lens 4 and impairing the transmittance of the lens or damaging it, as well as ejecting it from the nozzle hole 3 to the laser beam irradiation site. to prevent oxidation of the workpiece.

The present invention uses such a laser beam irradiation device and also uses another heat source, and FIG. 2 shows a case where a TIG arc is used as the heat source.

FIG. 2 shows an example in which the present invention is applied to heat treatment of rolling rolls, where T1 is a preheating TIG torch provided in front of the laser processing head 1, and T2 is the laser processing head l.
TIG torches for post-heat treatment installed behind the N1 and N
2 are the gas supply nozzles provided in the ~-chi T1 and T2, respectively; G1 and G2 are the nozzles N1 and N2;
The inert gases, Ac1 and Ac2, are supplied to the torches T1 and T2 and the workpiece (roll) R, respectively.
This is an arc that occurs between the surface Rs and the surface Rs. Further, RL is the rotating shaft, and LP is the heat-treated part.

In order to carry out the method of the present invention, the heat treatment area of the workpiece R must be heated by an arc Ac1 from a preheating TIG torch T1.
Preheat. At this time, the amount of thermal energy input into the heat-treated area is set to be smaller than the amount of thermal energy supplied from the subsequent laser processing head l. Next, the laser beam LB is irradiated from the laser processing head 1 onto the pre-treated area to perform heat treatment.

Figure 3 shows TIG torch, laser beam, and TI, respectively.
It shows the cross-sectional shape of the melted part due to G torch + laser beam heating, ATl is TIG 50A, 10V (7
) case, Ar1 is Ding IG 250A, l0V (7)
In the case, ALt indicates the case using a 2Kw laser beam, ALl4 indicates the case using a 3Kw laser beam, and ^TLI indicates the case when ATl and ALl are used together.
The case where ATl2L and Ar1 and Al1 are used together is shown.

These combinations are shown in Figure 4b. Figure 4a shows the relationship between the input energy amount and the melting cross-sectional area at this time.

As is clear from this figure, the laser 2Kw and TlG5
The composite welding cross-sectional area ALT1 with 0A is approximately equal to the welding cross-sectional area by laser 3Kw alone, 1°, or 4. In other words, in the method of the present invention, the workpiece is preheated with a TIG arc and then irradiated with the laser beam. , the efficiency of the laser beam can be increased. Also in this case, TIG 50
Since the melting cross-sectional area AT1 of A is much smaller than the melting cross-sectional area by the laser 2Kw alone (Ic/J%), the effect of composite melting is ultimately dominated by the melting characteristics by the Banyo laser beam, and therefore, the effect of composite melting becomes dominant. The processed area exhibits a crystal fast melting and solidification phenomenon due to the high energy density of the laser, and as a result, an ultra-fine structure can be obtained. Note that if the heat input by the TIG arc is 150 A or more, especially 250 A, the melting cross-sectional area correction will be larger than the melting cross-sectional area AL2 of the 2Kw laser, and as a result, the final characteristics of the molten area will be the same as that of the TIG arc. Therefore, in order to take advantage of the characteristics of the laser, it is necessary to increase the laser output or reduce the duration of TIG.

Further, in the present invention, after the laser beam irradiation, heat is applied to the processed region by a TIG torch T2 for post-heat treatment provided at the rear of the laser processing head l.

Figure 5 shows the temperature change of the processed part due to laser irradiation. When heat treatment (surface modification) of steel as described above is performed using a laser, the temperature changes as shown in the curved line in the figure. If cooling is performed at a relatively high rate, cracks may occur depending on the characteristics of the rust to be treated and the rust may become brittle, so it is necessary to perform slow cooling treatment. The method of the present invention is suitable for such cases, in which the TIG torch T2 for post-heat treatment is used to heat the steel to a temperature that does not melt it, and the cooling rate is set as shown by curve T in Figure 5 to prevent cracking. Occurrence can be prevented.

Next, examples of the present invention will be shown.

Example 1 1.4%C-0,7%5i-0,7%Mn-17%Cr
- After preheating the surface of a seamless pipe rolling plug containing 0.8% W-1.2% MO to a temperature of 600°C using a TIG arc, the surface layer was melted using a laser beam. Ta. When this plug is subjected to rolling, how long will it last until it cracks and is discarded?

It increased by 120% compared to the untreated one. On the other hand, T.I.
If preheating was not performed using a G arc, quench cracking occurred after laser beam irradiation, and the product could not be rolled.

Mistake 1.5%G-0.5%5i-0.5%Mn-25%Cr
- After preheating the surface of a plug for seamless pipe rolling whose main component is 3% Ni with a TiG arc to a temperature of 450°C, the surface layer is melted with a laser beam, and then with a TIG torch for post-heat treatment. It was then heated and slowly cooled. Compared to the plug of Example 1, this plug has a large amount of chromium carbide, so the effect of surface melting and rapid solidification treatment using a laser beam was remarkable, and this treatment increased the life until cracking approximately three times. In the case of this plug, T
Cracking after treatment could not be prevented unless postheating was performed in addition to preheating by IG arc.

Large lid ■l A guide shoe for seamless pipe rolling having the same composition as in Example 2 was also treated in the same manner as in Example 2. The life of this guide shoe was increased by 2.5 times compared to the untreated one.

Grain hoe soil 3.3%G-1.5%5i-2%M n-1%Mo and 3.5%ci, s%5i-0.5%Mn-0,4%N
i-Plug and guide shoe for seamless pipe rolling whose main component is 0.6% Cr whose surface temperature is 600℃
The surface was melted using a laser beam. This treatment doubled the lifespan until cracking occurred. In this case too, cracking occurred after laser treatment without preheating.

Big flag (9+15 0.85%G-0.8%5i-0.4%Mn-3,0%
The surface of a cooling roll mainly composed of Cr-0.3% Mo-0.1% V was preheated with a TIG arc torch to a temperature of 300° C., and the surface layer was melted with a laser beam.

Since the solidification structure was made ultra-fine, the surface roughness at the time of 500 tons of rolled steel improved to 175 compared to the untreated steel.

In the absence of preheating, cracking occurred after laser irradiation.

Lost Tane Takudan 3.0%G-0.5%5i-1.0%Mn-1.5%N
i-16%Cr-3%M.

The surface of a cold-rolled roll mainly composed of was heated to 400° C. by a TIG arc, and then the surface layer was melted with a laser beam. The roughness after rolling the steel material 500 was improved to 1/6 compared to the untreated material. It cracked without preheating.

] 11L 1.7%G-0.5%5i-0.9%Mn-1%Cr-
1%Ni-0.5%M.

TIG a hot-rolled roll mainly composed of
After preheating with an arc, the surface layer was melted with a laser beam. The roughness resistance of this roll was significantly improved, and the roll removal amount was increased to 173. In the absence of preheating, cracking occurred after laser irradiation.

Daigosarako 2.9%C-0.5%5i-1%Mn-18%Cr-1
After preheating the surface temperature of a hot rolling roll mainly composed of %MO-1%V-1%Ni to 700°C by TIG arc, the surface layer was melted by a laser beam, and further heated by TIG arc and slowly cooled. . The surface roughness resistance of this roll is even more remarkable than that of Example 7, and the amount of material removed per roll is 11% compared to that of the untreated roll.
Improved to 5. With this roll, cracks occurred after treatment unless preheating and postheating were performed.

In the above description and examples, a case was described in which a 1'IG arc was used as a heating source before and after laser irradiation, but a heat source other than a T'IG arc, such as high frequency heating, direct energization, gas burner, Any heat source can be used, such as a laser beam from a laser device other than the main heat source laser, and exactly the same effect can be achieved.

Fig. 1 is an explanatory diagram showing a laser beam irradiation method, Fig. 2 is an explanatory diagram showing an example of the present invention, and Fig. 3 is a cross-sectional diagram of a melted part by TIG torch, laser beam, and TIG torch + laser beam heating. figure.

FIG. 4a is a diagram showing the relationship between the input energy amount and the melting cross-sectional area in the case shown in FIG. 3, and FIG. 4b is a plan view showing the heating combinations shown in FIG. 3 in sections.

FIG. 5 is a diagram showing the temperature change of the processed part due to laser irradiation.

1: Laser processing head 2: Nozzle gas supply port 3: Nozzle hole 4: Condensing lens LB: Laser beam NG: Inert gas R: Workpiece R9: Surface T1: TIG for preheating Torch T2: TIG torch for post heat treatment N1, N2: Gas supply nozzle G1pG2'' Inert gas Ac1 p Ac2: Arc R: Rotation axis P; Heat treatment completed section Fig. 1 Fig. 2 Fig. 4a Fig. 4b Fig. 5 Time rsec-, 9 Procedure amendment (Voluntary) Director of the Japan Patent Office Kazuo Wakasugi 1, Indication of the case Patent Application No. 200227 of 1981 2
, Title of the invention Method for heat treatment of steel by high-density energy 3, Relationship with the amended case Patent applicant address 2-6-3 Otemachi, Chiyoda-ku, Tokyo Name (665) Representative of Nippon Steel Corporation Takeshi 1
) Yutaka 4, agent 104 Telephone 03-543-86945,
Drawing subject to amendment 6, contents of amendment

Claims (3)

[Claims] (1) In a steel heat treatment method in which a laser beam is irradiated onto the surface of the steel to melt the surface and modify the surface properties, the surface to be treated by the laser beam is heated using a separate heat source before and after irradiation with the laser beam. A method of heat treating steel using high-density energy. (2) Heating with another heat source before laser beam irradiation:
A method of heat treating steel using high-density energy as described in Patent No. (1), characterized in that the temperature is set so as not to exceed the amount of melting by a laser beam. (3) Heating by another heat source after laser beam irradiation:
A method of heat treating steel using high-density energy according to claim 1, characterized in that the temperature is set so as not to melt the steel and to maintain it at a predetermined temperature or higher.