JPS5964119A - Method of lineally heating stress relief of sheet - Google Patents

Abstract

PURPOSE:To perform efficiently a stress relief annealing, and to reduce discoloration caused by heating, by heating and cooling rapidly a sheet by a convergent plasma flame to give the shrinkage and deformation while sealing the back surface of a heated part with inert gas or nonoxidizing gas. CONSTITUTION:A plasma arc 5 is ignited between a sheet 1 and an electrode 2, and then a small range of the surface of sheet 1 is heated rapidly while sealing the back surface of a heated part with non-oxidizing gas such as inert gas, gaseous carbon oxide, and gaseous nitrogen, etc. to prevent the back surface from oxidation. The heat inputted to the local part by the plasma arc is rapidly diffused and cooled, and the oxidation accompanying discoloration is prevented.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is an object of the present invention, in which strain relief work is performed on thin outer panels of heavy-duty structures, etc., by rapidly heating and cooling the outer panels with a plasma arc to efficiently cause contraction and deformation. , relates to a heating strain relief method characterized by removing strain and applying tension to a vehicle outer panel.

[Prior art]

Conventional strain relief work involves restraining the outer panel by sandwiching it from both sides with electromagnetic magnets and metal pads, then heating it with a gas flame and cooling it with cooling water.
This is a method for removing distortion from thin plates. This boiling and quenching method is
This is inefficient because the outer panels are restrained from both sides. Moreover, the energy density of the gas flame is low and it is not possible to heat a local area like plasma heating, so if the strain relief part is heated at a strain relief temperature of 1, the temperature around the strain relief part 9 will also be heated. , a large amount of cooling water is required to cool these.

On the other hand, when strain is removed by heating the outer panel with a plasma arc after photometry, the heat input is concentrated in a local part of the outer panel, so distortion can be removed without heating the area around the heated part. Therefore, with the plasma heating method, there is no need to specifically water-cool the outer panel.
Just being pregnant was enough. However, recently, vehicles,
Increasingly, stainless steel and aluminum are used unpainted for roof plate members, side plate members, etc. of thin plate structures such as ships and buildings. Heat discoloration occurred not only on the surface of the heated portion but also on the back surface of the heated portion.

In the conventional method for removing distortion using plasma heating, the discolored parts that occurred due to removing distortion were scraped off with a knife. However, scraping off the discolored surface is a difficult task because the board is thin, and the surface finish is not good.

[Purpose of the invention]

The present invention eliminates the above-mentioned drawbacks, efficiently removes distortion υ in thin outer panels of vehicles, ships, etc., and eliminates discoloration removal work by suppressing discoloration of outer panels as much as possible. Ll:,-! The purpose is to facilitate the removal of discoloration.

[Summary of the invention]

The present invention eliminates distortion of thin outer plates of thin plate structures such as stainless steel pipes or aluminum used without coating by a heating method using a convergent plasma flame, and at the same time, the back side of the heated part is heated with non-oxidizing gas or water. The shield suppresses discoloration due to oxidation on the back surface of the heating section, thereby preventing discoloration removal work or facilitating discoloration removal work.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Figures 1 and 2 are based on theoretical values plus numerical calculations and experimental values. Figure 1 shows the temperature distribution over time when a mild steel plate with a thickness of 1.6mm is linearly heated. , Figure 2 shows the relationship between the heating width at the maximum temperature and the maximum shrinkage amount when a mild steel sheet with a thickness of 1.6 mm is linearly heated, and A shows the relationship between in-plane and out-of-plane buckling. This is the line that shows the limit. As shown in Figure 1, in order to heat a plate without causing out-of-plane buckling, the heating width must be narrowed to a width below the in-plane buckling limit line (A), ft, 1゜Also, in order to narrow the heating width and obtain a large contraction fA, it is necessary to heat in a very short time with a heat source with a density energy that has a locally converged heat distribution and little heat conduction. Must be.

From the above points, a heating method using a convergent plasma arc as a heat source, in which the arc converges with high-density energy and allows control of heat input, is very effective.

FIG. 3 explains the invention. 1 is a thin outer plate, 2 is an electrode, 3 is a plasma gas, 4II′i nozzle KL
5 is a plasma arc, 6 is a shield cover, and 7 is a shield gas. A plasma arc 5 is ignited between the thin outer plate 1 and the electrode 2 to rapidly heat a narrow area of the surface of the thin outer plate 1. The oxidation of the back surface of the thin plate is suppressed by enveloping it with a oxidizing gas.The heat input locally by the plasma arc is
As shown in the figure, it diffuses rapidly and becomes 300C or less 2 to 5 seconds after heating. Steel or stainless steel [3001m
'ld below: oxidation accompanied by discoloration does not occur. That is, if the back side of the heating section is shielded from heating with a non-oxidizing gas such as argon for 5 seconds, oxidation on the back side of the heating section can be significantly suppressed. On the other hand, the heating surface side is 1 x 1σ ~ 2 x 10"
Since it is exposed to the high temperature plasma arc of K, discoloration cannot be prevented even if it is shielded with shielding gas.

When thin plate structures such as vehicles, ships, and buildings are made of stainless steel sheets, they are corrosion resistant and can be used without anticorrosive coating, resulting in lower maintenance and servicing costs. On the other hand, stainless steel has poor thermal conductivity even though its coefficient of thermal expansion is higher than that of steel, so when a thin plate structure is manufactured, large out-of-plane deformation occurs due to welding heat.

Moreover, in the case of thin plate structures, a large number of man-hours are required for strain relief work to remove this out-of-plane deformation. For example, in a vehicle structure, out of the total assembly man-hours, 20 to 20 hours are spent removing distortion.
25%, and there is a need to improve the efficiency of the distortion removal work. If a discoloration-free distortion removal process for stainless steel plates is realized, the finished appearance of the structure will be improved, and the number of processing steps can be significantly reduced. stainless steel plate 1.5 rnln
When evaluating the heating conditions and the degree of discoloration on the back side of the heated part using Nakamata. On the other hand, the back surface of the heating section has a certain appropriate range even without gas shielding.

However, if the back surface of the heating section is shielded with a non-oxidizing gas such as argon, the appropriate conditions will be expanded. If the back side of the heating section is cooled with water to promote shielding of the heating surface and cooling of the heating surface, the range of heating conditions will be further expanded than in the case with shielding gas. Moreover, in the strain relief method using force n heat, the shrinkage deformation due to heating increases or decreases in accordance with the heat input per time. Therefore, if the back of the heating part is shielded with gas or cooled with water,
Compared to the case where the back side of the heating section is not gas-shielded, the efficiency of strain relief work is greatly improved, and discoloration due to heating is also suppressed.

〔Effect of the invention〕

According to the present invention, distortions such as welding distortions and local distortions existing in thin outer panels of thin plate structures such as vehicles, ships, and buildings can be efficiently removed. In addition, in a thin plate structure made of stainless steel sheet that can be used without painting, discoloration due to heating can be suppressed as much as possible, and discoloration removal work after removing distortion can be eliminated or discoloration can be easily removed. By applying the present invention, it is possible to reduce the number of man-hours required for strain relief work on a thin plate structure, and the finished appearance of the product is improved.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing the temperature distribution after heating of the joint heated with a plasma arc, and the relationship between the heating conditions and the shrinkage deformation that accompanies it. Figure 3 is a diagram showing the details of the present invention. FIG. 4 is a diagram showing changes in the appropriate condition range when the present invention is applied. 1... Thin outer plate, 2... Electrode, Death... Plasma arc, 7... Shielding gas. Agent Patent Attorney Toshiyuki Susuda 1st Figure 2 θ 24-1.8 Toguchi Ishin (A□. 3rd Figure 2 Figure 4 A, 7-1 Shoulder SI description FT ↓ θ 50/θθ 150 2ρρ Arairi Madenryo (A)

Claims (1)

[Claims] 1. Using a convergent plasma flame as a heat source that can limit the heating range and control the heat input, the thin plate is rapidly heated and cooled within a narrow range, and thermal expansion deformation is restrained in-plane to give contraction deformation to the heated part at the same time. Using a convergent plasma flame that can control the heat input as the heat source, the back side of the heating section is filled with inert gas or carbon dioxide gas, nitrogen gas, etc., and the thin plate is rapidly heated and cooled in a narrow range, resulting in υ-plane seating due to thermal expansion. The heated part undergoes shrinkage deformation by bending.