JPH04198739A - Inspecting method for re-melt treatment depth of al alloy cylinder head - Google Patents

Abstract

PURPOSE:To easily detect the re-melt treatment depth nondestructively by cutting a protruded section across a re-melt treated portion and an untreated portion, and applying buff polishing and etching treatment to a machined face. CONSTITUTION:The re-melt treatment consisting of the re-fusion process with a TIG arc device 11 and the quick cooling process is applied around the apex of a valve bridge section 7. The preset finish machining is applied to an exhaust valve hole 4 and an intake valve hole 5 across a re-melt treated portion 7a and a re-melt untreated portion 7b, and buff polishing 12 and etching treatment are applied to a mechanically machined face. The difference of irregularities between the machined face of the re-melt treated portion 7a and the machined face of the re-melt untreated portion 7b becomes remarkable, the difference of the light reflection characteristic is generated between the machined faces, and a contrast is generated between both of them. The re-melt treatment depth can be easily detected visually by this contrast.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for inspecting the remelt depth of an aluminum alloy cylinder head.

[Prior Art] In recent years, cylinder heads made of aluminum alloy have been widely used in order to reduce the weight of engines. However, when an aluminum alloy cylinder head is used in an engine with high output and high heat load, the valve bridge part (convex part) formed between the intake valve hole and the exhaust valve hole, or the sub-combustion chamber and the intake air There is a problem in that thermal fatigue occurs in the sub-combustion chamber bridge portion formed between the valve hole and the cylinder head, and the durability of the cylinder head decreases. However, in these bridging parts, the intake valve hole side is relatively low temperature, while the exhaust valve hole side or auxiliary combustion chamber side is relatively high temperature, so thermal distortion occurs in the bridge part due to the difference in thermal expansion. It is from.

In order to improve this problem, it is possible to take measures from the material standpoint, such as reducing the silicon content of the aluminum alloy and improving its elongation properties, but doing so would result in poor hot water flow during cylinder head casting. There are problems such as defects occurring or the strength of the cylinder head as a whole decreasing.

In addition, when casting the cylinder head, a chiller or water-cooled mold is placed around the bridge to increase the cooling or solidification rate of the aluminum alloy around the bridge, making the crystal grains finer and improving its elongation properties. Possible countermeasures include processing. However, if this is done, there is a problem that the structure of the mold becomes complicated. Also,
When using a chiller, there is a problem in that the cooling promotion effect is low, so that the effect of improving the elongation characteristics of the bridge portion cannot be sufficiently obtained.

Therefore, the bridge part of an aluminum alloy cylinder head cast by a conventional method is irradiated with a high-density energy beam such as TIG arc or laser to remelt the bridge part and then rapidly heat the unmelted part. The remelted part is rapidly solidified by conduction, creating a chilled structure with small crystal grains in the bridge part, improving the elongation characteristics of the bridge part.
A method of remelting an aluminum alloy cylinder head has been proposed (see, for example, Japanese Patent Laid-Open No. 193773/1983).

[Problems to be Solved by the Invention] However, in conventional aluminum alloy cylinder heads that have been subjected to such remelt treatment, there is a problem in that there is no method for non-destructively inspecting the remelt treatment depth. However, there is no material difference between the remelt treated part and the non-remelt treated part other than the difference in grain size, so conventional non-destructive inspection methods using magnetism, X-rays, etc. cannot detect the boundary between the two. This is because it cannot be detected.

Therefore, it is not known whether the cylinder head has been remelted to a predetermined depth or not, resulting in a problem that the accuracy of quality control of the cylinder head is reduced.

The present invention has been made in order to solve the above conventional problems, and provides an inspection method that can easily and non-destructively detect the depth of remelt treatment of an aluminum alloy cylinder head that has been subjected to remelt treatment. The purpose is to provide.

[Means for Solving the Problems] In order to achieve the above object, the present invention performs a remelting process consisting of a remelting process and a quenching process around the top of the convex part forming the Al alloy sonorinda head combustion chamber. Then, the cylinder head is machined to remove a part of the convex part across the remelt treated part and the non-remelted part, and then the machined surface that has been machined is buffed. At the same time, the polished surface is etched with an etching solution, and the depth of the remelt treatment is detected by using the difference in light reflection characteristics between the remelted surface and the unremelted surface. A method for inspecting the depth of remelt treatment of an A12 alloy cylinder head is provided.

In the above configuration, the timing at which the etching treatment is performed is not particularly limited as long as it is not before the buffing, and may be at the same time as the buffing or after the buffing is completed.

[Operations and Effects of the Invention] According to the present invention, a convex portion is shaved from a remelted portion to an unremelted portion, and buffing is performed on this shaved surface. Since the crystal grains are smaller than those of the unremelted portion, after polishing, the processed surface of the remelted portion has smaller irregularities and is smoother than the processed surface of the unremelted portion. After this, an etching process is applied to the machined surface, but this etching process corrodes the machined surface, and the difference in unevenness (roughness) between the machined surface of the remelt-treated part and the machined surface of the unremelted part becomes more noticeable. Become. For this reason, there is a difference in the light reflection characteristics of the processed surface between the remelt treated part and the unremelted part,
A contrast arises between the two. Therefore, the depth of the remelt treatment can be easily detected visually based on this contrast.

In addition, when performing buff polishing, the edges of the top surface of the convex portion are polished and rounded (to form an R shape), so stress concentration on the edges is reduced after installation in the engine, and the cylinder head Durability is increased.

[Example] Examples of the present invention will be specifically described below.

As shown in FIG. 2, a cylinder head l for a four-cylinder diesel engine is cast by a low-pressure casting method using an aluminum alloy (JISAC JD material). The cylinder head 1 is provided with an auxiliary combustion chamber 3, an exhaust valve hole 4, and an intake valve hole 5 at positions corresponding to the combustion chambers 2 of the first to fourth cylinders #1 to #4, respectively. It is being Here, the exhaust valve hole 4 and the intake valve hole 5 are each formed by rough machining.
It is formed with a finishing allowance of about the size of an opening left. Note that, ultimately, each sub-combustion chamber 3 is provided with an injection port 6, respectively.

In this way, the cylinder head 1, which has been roughly machined after casting, has the valve bridge portion 7 formed between the exhaust valve hole 4 and the intake valve hole 5, the auxiliary combustion chamber 3, and the intake valve hole. 5
The bridge part A, which includes the auxiliary combustion chamber bridge part 8 formed between Furthermore, it is inspected whether the remelt treatment has been carried out to a predetermined depth. In addition, the valve prism part 7 and the auxiliary combustion chamber bridge part 8
corresponds to the convex portion described in claim 1, respectively.

Hereinafter, with reference to the process diagram shown in FIG. 1, the remelt treatment method and inspection of the remelt treatment depth for the valve bridge portion 7 between the exhaust valve hole 4 and the intake valve hole 5 of the cylinder head 1 will be explained. The method will be explained.

(1) Step 1 Using the TIG arc device 11, the valve bridge portion 7 is irradiated with TIG arc to remelt the area around the top of the valve bridge s7. The TIG processing conditions are as follows.
When the arc irradiation ends, the heat of the remelted portion rapidly moves to the surrounding unmelted portion by conduction, and the remelted portion rapidly solidifies to become the remelted portion 7a. In the remelted portion 7a, the crystal grains are made finer than in the non-remelted portion 7b, and a chilled structure with excellent elongation properties is generated.

(2) Step 2 The cylinder head l (see Figure 2) is subjected to T6 treatment consisting of a hardening process and a tempering and aging process to increase its strength.

■Step 3 Using a drill, perform a predetermined finishing process on the exhaust valve hole 4 and the intake valve hole 5. At this time, the inner circumferential surfaces of both holes 4.degree. 5, that is, both side surfaces of the valve bridge portion 7, are slightly scraped off across the remelt treated portion 7a and the unremelted portion 7b. Note that this finishing process corresponds to the machining process described in claim 1.

■Step 4 Buffing and etching are performed on both sides of the shaved valve bridge portion 7. Here, alumina particles of 200 mesh or less are used as an abrasive for buffing, and an aqueous solution of about 1% sodium hydroxide is used as an etching solution for etching. Specifically, first, only buffing is performed using the buffing device +2 to bring the surface roughness of the side surface of the valve bridge portion 7 to Is or less. Next, while buffing is being performed, an etching solution is sprayed onto the polished surface through an etching solution supply passage (not shown) formed in the rotating shaft of the buffing device 12, thereby performing an etching process.

Here, when buffing is performed on both sides of the valve bridge portion 7, the remelt treated portion 7a has small crystal grains, so the surface irregularities become relatively small (smooth), while the unremelted portion 7b has crystal grains. Since the grains are large, the surface becomes more uneven (rougher).

When the etching process is performed, both sides of the valve bridge part 7 are corroded, so the remelt part 7
The difference in unevenness between a and the unremelted portion 7b becomes more significant.

FIG. 3 shows an example of the surface condition of the remelt treated portion 7a and the unremelted portion 7b which have been subjected to valve polishing and etching treatment. As is clear from FIG. 3, the surface of the remelt-treated portion 7a has almost no irregularities, but the unremelted portion 7b has irregularities with a depth of about 1 μm.

Therefore, there is a difference in light reflection characteristics between the surface of the remelt-treated portion 7a and the surface of the non-remelt-treated portion 7b, and a contrast occurs between the two.

Therefore, the depth of the remelt treatment can be easily grasped visually, and it can be determined whether or not the predetermined remelt treatment has been performed. If only the cylinder heads 1 for which the remelt treatment has been determined to be sufficient through such visual inspection are transferred to the next process, the quality of the cylinder heads 1 can be improved, and the reliability of the ennon can be improved.

By performing buff polishing, the edge 7C at the top of the valve bridge part 7 is completely smoothed out and becomes rounded, so that stress concentration on the edge 7C at the top of the valve bridge part 7 will be avoided later when the cylinder head is assembled. The durability of the cylinder head 1 is increased.

■Process 5 Valve holes 13.1 are installed in the exhaust valve hole 4 and intake valve hole 5, respectively.
Press in 4.

In this embodiment, the etching process is performed during buff polishing, but the etching process may be performed in a separate step after the buff polishing is completed.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an embodiment of the present invention, from remelting a cylinder head to press-fitting a valve. FIG. 2 is an explanatory bottom plan view of the cylinder head in which the remelt treatment depth according to the present invention is inspected. FIG. 3 is a diagram showing the surface condition of the remelt treated portion and the unremelted portion after buffing and etching treatment. A...Bridge part, #l~#4...1st to 4th cylinders, 1
,・Cylinder head, 2・Combustion chamber, 3・Sub-combustion chamber, 4・
- Exhaust valve hole, 5... Intake valve hole, 7... Valve bridge part, 8... Sub-combustion chamber brittle part, 11... TIG arc device, 12... Buffing device.

Claims (1)

[Claims] (1) A remelt process consisting of a remelting process and a quenching process is performed around the top of the convex part that forms the combustion chamber of an Al alloy cylinder head, and then the remelt process and non-remelt process are performed on the cylinder head. After that, the machined surface that has been machined is buffed, and the polished surface is etched with an etching solution. The remelt treatment depth of an Al alloy cylinder head is characterized in that the remelt treatment depth is detected by utilizing the difference in light reflection characteristics between the machined surface of the remelt treated part and the machined surface of the unremelted part. How to test.