JPS59185589A - Adhering and bonding method of cast iron member - Google Patents

Abstract

PURPOSE:To accomplish reliable joining at a low cost in the stage of joining a cast iron member and a cast iron or other kind of metallic material by heat- treating the former by using a Cr acid, interposing a joining agent of a Cr compd. between both members and subjecting the members to a heat treatment. CONSTITUTION:A cast iron member is first dipped in a warm aq. soln. of a Cr acid to bring the graphite part exposed or connecting on the surface of the member and the Cr acid into reaction, thereby removing the graphite. The solvent sticking on the surface of such material is lightly wiped away and the member is heat-treated in an electric furnace, then the extremely thin Fe2O3 and Cr2O3 film including pinholes formed by decarburization is formed over the entire surface of the member. A concd. aq. soln. of a soluble Cr compd. or a slurry prepd. by adding a small amt. of >=1 kind of fine powder of metallic oxides such as ZnO, MgO or the like is coated on at least one surface of the joint surfaces between the members. The joint surfaces are joined and fixed and are subjected again to a heating treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention improves the airtightness and combination properties of complex shapes of cast iron members used for cylinder heads, cylinders, pistons, intake and exhaust parts, etc. of various internal combustion engines, and also improves the airtightness and combination properties of aluminum alloy members. The present invention also relates to a method for adhesively bonding cast iron members to cast iron, aluminum alloys, or other metal members in order to improve the heat resistance and wear resistance of other metal members and to reduce costs.

Conventionally, cast iron has been widely used in various industrial fields because it is inexpensive and has excellent castability and photographic absorbability, and is particularly popular as a component for industrial machinery and internal combustion engines. However, on the other hand, the field of application for parts requiring a combination structure is considerably limited due to the poor joining properties of cast iron to each other and cast iron to other metals such as brazing, welding, and fusion welding.

For example, recently, the top of an aluminum alloy cast piston in a diesel engine (d) is required to have improved heat resistance and wear resistance due to the increasing heat load. However, these combination methods can cause damage due to rapid heating during manufacturing, cracks due to insufficient fusion, and "backlash" due to high temperatures during engine operation. However, there are still many problems in terms of reliability and price.

Therefore, in order to utilize the advantages of cast iron such as castability, vibration absorption, price, etc., as well as heat resistance and wear resistance, the inventor proposed a method for joining cast iron with cast iron, aluminum alloy, or other types of metal members. As a result of repeated research, cast iron parts are immersed in an aqueous chromic acid solution and heated, and then a bonding agent consisting of a concentrated solution of soluble chromium compound is interposed between the parts to be joined.
It has been found that heat treatment at a relatively low temperature results in extremely effective bonding17. That is, when joining a cast iron member to a cast iron or other metal member, the cast iron member is immersed in a hot aqueous solution of chromic acid and subjected to heating treatment. After lightly wiping off the solution adhering to the surface of the treated object, it is heat-treated in an electric furnace. A concentrated aqueous solution of a soluble chromium compound or a slurry containing a small amount of fine powder of a metal oxide in this solution is applied to at least one of the joint surfaces of the cast iron member after this treatment and the cast iron or other metal member. After coating, the joining surfaces are brought together and heat treated again to join.

Next, the present invention will be explained in more detail.

The cast iron members used in the present invention include ordinary cast iron, tough cast iron, malleable cast iron, alloy cast iron, and examples thereof include gray cast iron, ductile cast iron, mariable cast iron, and nickel cast iron. Next, the metal members to be joined to such a cast iron member are the above-mentioned cast irons, steels, aluminum alloys, and copper alloys, such as the above-mentioned cast irons, carbon steel, nickel steel, nickel chromium S, steel, brass, Examples include Sirumin, Roex, Y alloy, etc. The structure of iron is different depending on the alloying elements contained and the thermal history.
In general, iron transformations such as ferrite, pearlite, martensite, and troostite (cementite) (Fe3C),
It is made of graphite, etc.

This Fe5C and graphite do not wet with the metal melt, generate CO2 gas in high humidity, and furthermore, their structure changes when exposed to high temperatures. has left many impressions.

Therefore, first, a cast iron member is immersed in a hot aqueous solution of chromic acid and heated to remove the Fe exposed on or in contact with the surface of the member.
Fe5C and graphite are removed by reacting 5C and graphite with chromic acid. The reaction rate of this reaction between F'ejC and graphite with an aqueous chromic acid solution is very slow at temperatures around room temperature, so it is necessary to use a hot chromic acid solution, and a suitable temperature is 70 to 100°C. It is. Also, the soaking time may vary depending on the size and heat capacity of the parts.The concentration of chromic acid is 1.3 to 1.6 with a specific gravity.
It is a title.

The cast iron member from which the carbon component on the surface has been removed in this manner is not washed with water, but the excess solution adhering to the surface is gently wiped off, and heat treatment is performed in an electric furnace. The heat treatment is preferably carried out at a temperature of 500 to 600°C. The atmosphere in the shredder should be neutral to oxidizing. This heat treatment causes dehydration of H2CrO4, CrO3→Cr2O
Due to the conversion reaction in step 3, a very thin layer of Fe2O3 is formed on the entire surface of the cast iron member, including the pinholes formed by decarbonization.
An oxide film of Cr2O3 and . For example, 5 to 10% N
Washing is performed using an aOH solution, and then oxides on the υ surface are removed using 6NHCt and an acidic agent is applied. In addition, after the chromic acid aqueous solution immersion treatment, take it out from the solution and immediately wash it thoroughly.
Even if this part is fully plated with nickel and further heated with residual heat to form a nickel oxide film, a good bond can be obtained using the bonding material described later.

In addition, for other metal members, such as carbon steel and copper alloy members, the joints are plated with nickel or chromium, and this is heat treated to form an oxide film, and for small aluminum alloy members, the joint surfaces are coated with nickel or chromium. A good bond can be obtained by applying zinc plating to the surface, followed by nickel plating on top of the plate, and then forming the same coating as described above, or by applying an anodic oxidation coating, using the bonding agent described later.

Next, the bonding agent used to bond each member is a concentrated aqueous solution of a soluble chromium compound, or a slurry in which a small amount of one or more fine powders of metal oxides is added to this solution, such as ZnO, MgO, etc. Or 1 year old 6 pieces of CaO or one or more types in total amount of 0.15 to 0°5 per 1 mole of H2CrO.
A concentrated aqueous solution of a chromium compound prepared to have a specific gravity of 1.65 to 1.7 by dissolving mol.
A total of 5 to 10% by weight of at least one of powders of 0r5, Cro3, and Fe2O3 with a particle size of 44 μm or less, preferably 1 μm or less is added to the above-mentioned concentrated solution, and the mixture is thoroughly ground and mixed using a grinder. This is slurry made by

Apply this bonding agent well to at least one of the joining surfaces of the members, preferably to the surfaces of both members, and
Both members are pasted together and set in an electric furnace in a fixed state, and the temperature is increased by 3 to 7°C/min to perform heat treatment. Note that the heat treatment temperature is not constant depending on the type of member. For example, in joining a cast iron member and an aluminum alloy member (ROEX), the maximum temperature is set at 500''C, but the holding time is not constant depending on the size K of the member.

Further, the atmosphere during heat treatment is not particularly limited, but for example, in the case of joining with copper alloy or aluminum alloy members,
It is preferable to use a neutral to non-oxidizing atmosphere above 0°C.

Now, as an example, when joining gray cast iron and carbon copper, first, if you look at the surface of the gray cast iron before treatment using a microscope (x500), you will notice that many black spots, that is, graphite, are formed as shown in Figure 1. . When this gray cast iron is treated with H2CrO, pores are formed by degraphitization as shown in FIG. 2 (the centers of the spots shine white because of the vacancies). Therefore, when looking at the cross section of a jointed body made of gray cast iron and carbon fiber produced by the method of the present invention, as shown in Fig. 3, gray cast iron 1 and Cr
It can be seen that the 2O3-based bonding layer 2 is firmly bonded.

That is, if the surface is not treated with kH2CrO4, streaks due to an air layer will appear on the joint surface. Note that 3 is a carbon button.

As described above, the present invention removes carbonaceous substances present on the surface of a cast iron member by treatment with a heated chromic acid concentrated aqueous solution, and then heat-treats the joint surface to remove Fe2O2 and Cr2.
By forming a thin oxide film of O3, interposing a concentrated solution of a chromium compound between joints with similarly treated cast iron or other types of metal parts, and performing heat treatment at a relatively low temperature, it is extremely difficult to join. It is industrially suitable because a cast iron member and another member can be joined through a relatively simple process to obtain a joined product with strong joint strength.

Next, the present invention will be explained in more detail with reference to Examples.

Example-1 (Method of joining cast iron members and cast iron members) (1)
Treatment of cast iron parts Two square plates made of ductile cast iron (all 30 x 30 x 107M7W) were thoroughly washed with a 10% NaOH aqueous solution, and then immersed in a 6NHC/=aqueous solution for about 3 minutes to dissolve the oxides on the surface. and roughened.

This was immersed in an aqueous solution of H2CrO, specific gravity 1.5, at about 100°F and heated for about 3 minutes, then the excess solution adhering to the surface was gently wiped off, and the solution was heated at 580°C using an electric furnace.
The heat treatment was completed by maintaining the temperature at CK 30 min.

(2) Preparation of bonding agent Dissolve 3100g of CrO in water to make a concentrated aqueous solution of H2CrO4, and add 15gr of ZnO and MgOlogr to this.
The powder was added little by little and dissolved, and water was added to this to prepare a solution with a specific gravity of 1.68. Next, this solution 100
For gr, TlO2 powder of 10 μm or less 4? and 5μm
A total bonding agent was prepared by adding 3 g of the following 8i02 powder and grinding and mixing for 24 hours using an alumina ball mill. (3) Bonding procedure Both bonding surfaces (30X 30mrn) using a brush, and after about 4 minutes, both jointed surfaces were brought together, tied and fixed with fine wire, and heated at 5° (T/mrn) using an electric furnace.
Increasing the temperature at 580°CVC for 3Qmin
A strong bonded body was produced by heating and holding.

This bonded body was heated at 550°C for 11 hours at room temperature.
The hr rapid cooling/heating test was repeated 10 times using an electric furnace. This sample was adhered to a test bar using an epoxy resin adhesive, and a tensile bonding strength test was conducted. As a result, destruction occurred at the resin bonded surface and showed a value of 420KqlCTL2 or more.

Example-2 (Joining of cast iron member and aluminum alloy member) m Treatment of cast iron member Gray cast iron (equivalent to JISFC-'75) was 30 x 3
A square plate processed to a size of 0 x 6 x m was prepared in (1) of Example-1.
The surface was cleaned and completely roughened using an acidic agent in the same manner as described above, and then Fe5C and graphite were removed using heated H2CrO and solution, and then heat-treated at 550°C for 25 mtn to obtain a specimen. And so.

(2) Treatment of aluminum alloy members A block of commercially available hypersilumin aluminum alloy castings processed into a size of 30 x 30 x 10 mm was prepared by H, So.

An anodic oxide film with a thickness of 55 μm (7) was applied using an electrolytic solution to prepare a specimen.

(3) Dissolve the adhesive CrCrO31O0 in water to create a concentrated aqueous solution of -(H2CrO4, add and dissolve fine powders of ZnO12@, MgO5S' and CaCO3122 little by little to this,
It was diluted with water to give a specific gravity of 1°66. Next, this solution 1
00L? Add 3f of Al2O3 powder of 10 μm or less to
A bonding agent was prepared by grinding and mixing for 24 hours using a ball mill.

(4) Joining procedure Both joining surfaces of the members described in (1) and (2) (30 x 3
f) Apply the bonding agent described in item (3) to rnm) well, overlap the two bonded surfaces on the left edge for about 3 minutes, and fix.
It was set in an electric furnace, the temperature was raised at 5''C/min, and the temperature was maintained at 490''C for 30min to produce a bonded body.

This bonded body was repeatedly heated and cooled 10 times by heating at 500"C for 11 hours and air cooling at room temperature for 1 hour. A test piece with a joint surface of ICrrL x ICrIL was cut from this sample and tested using epoxy adhesive. When it was adhered to a rod and the tensile bonding strength was measured, it was found that peeling occurred at the resin adhesive surface and an average value of 3g5K!77cm2 or more was obtained.

[Brief explanation of drawings]

Figure 1 is an R-angle photograph showing the surface of gray cast iron before treatment.
FIG. 2 is a photomicrograph showing the surface of gray cast iron treated with an H2CrO3 solution, and FIG. 3 is a photomicrograph showing a cross section of a joined body of gray cast iron and carbon steel produced by the method of the present invention. 1... Gray cast iron, 2... Cr2O3-based bonding layer, 3
...Carbon steel patent applicant Usui Kokusai Sangyo Co., Ltd. Voluntary procedure amendment 1. Indication of the case 1982 Patent Application No. 61660 2 Title of the invention Adhesive bonding method with cast iron parts 4 Agent Ginza Building (561-), 3-3-12 Ginza, Chuo-ku, Tokyo
5386・0274) (7390) Patent attorney press 1) Good
Ku Amended Hair Patent Application 1986-61660 1, Specification page 7, line 1 rZnos J Y rZro
t”. 2, page 7, line 2 rCro, j? rc r, O
Correct as s J. 3, page 12, line 10 [Ht Cr Os J Y
[Corrected as H*Cr04J. Voluntary procedure amendment 1, indication of the case 1982 Patent Application No. 6166CJ 2, name of invention Method of adhesive bonding with cast iron parts 4, attorney 8, content of amendment as attached. 61660 1. Delete "rFegC and" on page 4, lines 19 and 20, and "rFe*c and" on page 11, line 11 and line 18 of the detailed letter 4. 3. Page 7, line 20, page 8, lines 6, 7, 1
On page 2, lines 9, 10, 12, and 14, "mouse" is corrected to "ductile."

Claims (1)

[Claims] When joining cast iron parts to cast iron or other metal parts, the cast iron parts are immersed in a hot water solution of chromic acid in advance, and then heat treated in a furnace, and then the joint surfaces of the mutual parts are heated. A simple concentrated aqueous solution of a soluble chromium compound or a slurry containing a small amount of one or more fine powders of metal oxides in the concentrated aqueous solution is applied to at least one of the surfaces, and the joint surfaces are brought together again. Adhesive bonding method with cast iron parts that requires heat treatment.