JPH07331400A - Remelting treatment of metal surface - Google Patents

Abstract

PURPOSE:To secure the necessary treating depth in the min. limit in a remelting treatment method. CONSTITUTION:At the time of shifting a TIG arc by reforming a recessed part 5 having the necessary treating depth in the min. limit or the depth shallower than the above depth at a position 7 which needs the deep treating depth on the surface layer to be treated in the position forming the recessed part 5, the TIG arc is approached to the surface to be treated at the position nearer than the other position. In the case of being the same input heat quantity, the penetration volume is constant, and therefore, the recessed part 5 is arranged in the position to be treated and the treatment is executed by bringing the torch 1 close to the recessed part at the position to be treated nearer than the other position, in which the recessed part 5 does not exist. By this method, the penetration volume having the same volume of the recessed part 5 is intruded downward at the recessed part 5 to increase the penetration depth, and the depth as the standard value can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a remelting treatment method for locally modifying a part of a metal surface layer such as an aluminum alloy casting.

[0002]

2. Description of the Related Art A member having a complicated shape such as a cylinder head is usually formed by casting. However, since the cast product contains internal defects such as porosity and has a coarse structure, a product with high fatigue strength cannot be obtained as compared with a forged or press-formed product. In order to improve the fatigue strength of casting products, while reducing internal defects,
It suffices to refine the crystal grains. And, in order to make the crystal grains fine, it is sufficient to increase the cooling rate during solidification, but if the cooling rate is increased, not only the moldability of the casting such as the flow of molten metal and the molten metal is hindered, but also the internal The defect may be frozen and remain inside.

In the production of an aluminum alloy cylinder head, after it is once formed by casting, the portion where fatigue strength is particularly required is irradiated with high density heating energy such as TIG arc, laser beam, electron beam or plasma arc. A method for locally modifying the surface layer by re-melting it and then rapidly solidifying it is disclosed in JP-A-61-161.
It is proposed in Japanese Patent No. 193733. This local surface modification method is called "remelting treatment" or "remelting treatment".

In Japanese Patent Laid-Open No. 3-471, in butt joint TIG welding of an aluminum alloy, there is a first region where the arc length and the penetration depth are almost inversely proportional, and the penetration depth is longer when the arc length is longer than the first region. Using a welding power source with a substantially constant current characteristic such that a second region where the arc length hardly changes and a third region in which the penetration depth is approximately proportional to the arc length with an arc length longer than the second region are obtained, the arc length is A control method of TIG welding in which the arc length is periodically changed so as to alternately enter into at least two or more regions of the first to third regions is described. In this method, the welding current is kept constant. It is possible to control the penetration depth.

TIG arc melting is usually used for the remelt processing. This is because the apparatus is inexpensive and the occurrence of blowholes during melting is small. But TIG
The remelting process by arc melting has a problem of poor dimensional accuracy. Especially for parts with complicated shapes such as cylinder heads, the size is constrained by the valve seat and water jacket. High accuracy is required.

FIG. 4 shows the condition of the remelt processing section in the cylinder head. 22 is an exhaust port, 23 is an intake port,
Reference numeral 24 is a plug hole, and 25 shows the shape of the surface to be remelted. In the remelt processing section, for example, A in the figure,
At points B, C, and D, in addition to the shape of the surface, there are dimensional constraints on depth (standard of depth).

FIG. 5 shows the standard regarding the depth of the processing portion and the result of the remelting process by the conventional remelting method. FIG. 5A shows a state before processing, and FIG.
Indicates the state after processing. In FIG. 5A, 26 is a TIG
Torch, 27 is a welding wire or a consumable welding rod,
The remelt processing is performed on the base material to be processed 28 by drawing a linear locus shown by 29. At this time, the depth of the remelt processing part depends on variations in the welding environment (earth position, material of the earth plate), welding conditions (TIG torch speed, applied voltage, current, input amount of welding rod, etc.) and the remelt welding robot. Variation occurs due to a teach-in error, a setting error of the base material to be processed, and the like, and the shape of the depth of the remelt processing portion after the processing is as shown in FIG. 5B.

In FIG. 5B, reference numeral 30 designates a portion where the base material is locally reformed by remelting treatment, and a one-dot chain line 31
The portion indicated by is a portion where the dimension is constrained by the depth standard, and 32 is a line indicating a portion to be removed by the processing after the treatment. The range indicated by e is the range restricted by the depth dimension standard, and g is the minimum depth dimension determined by the standard. The range indicated by e indicates the range of depth variation caused by the remelt treatment. In the portion 30 where the base material 28 to be treated is locally modified, the line indicated by 33 shows the deepest variation range, and when mass production is performed by repeating the remelting treatment continuously, the variation in the depth is It is shown that the area is within the range of d in the direction shallower than the above line.

Here, the problem is that the range of f occurs, and this part deviates from the range determined by the dimensional standard, and it means that a process with a shallow depth occurs in mass production. This indicates that the mass-produced products include defective products having a insufficient processing depth at a constant rate. Therefore, it is inevitable to perform 100% inspection in the conventional remelting process, and a large amount of cost is required to deal with the defective product. However, since the value of d is smaller than the value of e, it indicates that if the average value of the variation in the depth of the remelting process shifts to the deeper side, all of the values fall within the standard values.

[0010]

DISCLOSURE OF THE INVENTION The present invention prevents the occurrence of defective products due to the insufficient remelt processing depth, which occurs in the mass production process, and the associated large cost, and
It is an object of the present invention to provide an efficient remelt processing method using G arc.

[0011]

DISCLOSURE OF THE INVENTION The present invention provides a metal surface with T
In a method of applying an IG arc to remelt the surface layer and subsequently reforming the surface layer by rapid solidification, the area of the surface layer to be processed needs to have a minimum required depth in advance. When a concave portion having a treatment depth or a shallower depth is formed and the TIG arc is moved, the TIG arc is moved closer to the surface to be treated than other portions at the portion where the concave portion is formed, and remelting treatment is performed. This is a method for remelting the metal surface.

[0012]

In the remelting process, the penetration depth is affected by the heat input amount shown below. Therefore, if the amount of heat input is the same, the penetration volume remains unchanged. Here, when a concave portion is provided in the portion to be treated and the torch is processed closer to the portion to be treated than in other portions where there is no concave portion, the penetration volume corresponding to the volume of the concave portion is below the concave portion. The penetration depth increases and the standard depth can be maintained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of an embodiment for carrying out a remelting process according to the present invention, and FIG. 1A shows a state before the process.
B shows the state after processing. In FIG. 1A, 1 is TIG
The torch 2 is a tungsten welding rod, both of which are at the processing start position. The line indicated by 3 is a path drawn by the TIG torch 1 when performing the remelting process, and is substantially parallel to the concave portion 5 formed at the position of the line indicated by 7 of the base material 4 to be processed where the standard value of the processing depth is provided. It is an attempt to move along a different trajectory.

In FIG. 1B, 6 is a penetration portion where the base material is locally reformed by remelting treatment, and 8 is a line showing a depth removed by processing after the treatment. c is the minimum depth determined by the standard, the range indicated by b is the range of the depth standard, and the range indicated by a is the range of depth variation caused by the remelt treatment. The position shown by the line 7 in the penetration portion shows the deepest one in the range of variation, and when mass production is repeated by repeating the remelting process,
The variation of the depth indicates that it enters the range of a in the direction shallower than the above line. This is because the recesses of the minimum required processing depth or a shallower depth are formed in the base material to be processed at the processing depth position determined by the standard, so that the dispersion of the processing in mass production is included. However, it means that there is no defective product whose processing depth is out of specification.

FIG. 2 shows the penetration depth of the remelting process according to the present invention. Generally, the penetration depth is affected by the heat input amount shown in the above equation. However, even if the amount of heat input is the same, as shown in FIGS.
Depending on the heat transfer and other conditions, the penetration shape is 10 and 1.
Although it may change as shown by 1, the penetration volume remains unchanged. FIG. 2C and FIG. 2D are views showing the situation before and after the recess 12 which is smaller and deeper than the diameter of the TIG torch is provided in the processing part in advance and the remelting process is applied to this part.
Shows before processing and FIG. 2D shows after processing. If the line indicated by 13 has a shape determined by the standard, the shape indicated by 14 becomes the penetration portion, and the volume corresponding to the concave portion 12 advances below the penetration portion and increases, and the concave portion of 12 must be present. If the depth is insufficient and the diameter of the recess is smaller than the torch diameter, the recess is absorbed by the welded portion and no problem occurs.

FIG. 3 shows an example in which a large-diameter shallow recess is added to a small-diameter recess. FIG. 3A shows a penetration portion 17 formed by a single small-diameter recess 16, and FIGS. 3B and 3C show a small-diameter recess having a smaller depth and larger-diameter, shallower recesses 18, 2.
0 is additionally provided, and in these concave portions, the TIG torch is processed closer to the base material to be processed, and the depths of the obtained penetration portions 19 and 21 are as shown in FIG. 3A.
17 is almost the same, which means that there is a degree of freedom in the shape of the preformed recess.

Regarding the formation of the recess before the remelt treatment,
If the target base material is a cast product, the recess is formed in the base material by the shape of the mold, and if it is difficult to form as a cast product, this is formed by machining, but in the case of a cast product Since it is impossible to form a deep recess having a small diameter, in this case, the degree of freedom of the shape of the recess is utilized.

[0018]

INDUSTRIAL APPLICABILITY According to the present invention, in the remelt treatment for locally modifying the surface layer, the penetration depth for modification is increased to prevent the occurrence of defective products due to insufficient penetration depth. Efficient remelt processing can be performed by reducing the associated defect cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a penetration volume of the present invention.

FIG. 3 is an explanatory view of the effect of the concave portion of the present invention.

FIG. 4 is an explanatory view of the shape and standard of a processing unit.

FIG. 5 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1 TIG torch 2 Welding rod 3 TIG torch trajectory 4 Base metal 5 Recess 6 Remelt process Penetration part

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C22F 1/04 L C23C 6/00 F02F 1/24 B

Claims (1)

[Claims] 1. A method of applying a TIG arc to a metal surface to remelt the surface layer and subsequently modifying the surface layer by rapid solidification, wherein a portion of the surface layer to be processed which requires a deep processing depth is previously processed. When a TIG arc is formed by forming a recess having a minimum required processing depth or a depth shallower than that, a TIG is formed in the part where the recess is formed.
A method for remelting a metal surface, characterized in that the arc is moved closer to the surface to be treated than other parts to perform the remelting treatment.