JPS5950172A - Nitrided cast iron parts and its production - Google Patents

Abstract

PURPOSE:To produce nitrided cast iron parts having high resistance to corrosion, particularly high resistance to corrosive wear, by grinding the surface of a cast iron blank material after nitriding and coating and rubbing a resin incorporated therein with a sacrificial corrososive metal on said surface then subjecting the material to a heat treatment. CONSTITUTION:The surface of a cast iron blank material 14 is subjected to soft nitriding to form a nitrogenous compd. layer 10 on the surface and said layer is hardened. Then the parts 12 of graphite which is the compsn. of the material 14 build up. Clearances are generated between the graphite 12 and the base material 14 around said graphite owing to thinning of the graphite. The build- ups on the surface are honed to a smooth surface. A resin contg. a specific ratio of a sacrificial corrosive metal, for example, an epoxy resin is coated on the surface and after the resin layer 15 is dried, the layer is subjected to rubbing with a rubber grindstone and is subjected to a heat treatment in the atmospheric air. Then the exposed parts of the graphite are sealed by the resin parts 16.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nitrided cast iron product with improved corrosion resistance and a method for manufacturing the same.

It is well known to perform nitriding treatment to improve the wear resistance of cast iron. For example, in order to impart wear resistance to the wall surface of a cast iron cylinder of an automobile ennon, it is an effective means to completely harden the surface by subjecting it to nitriding treatment. but,
When nitriding is performed, the base material bulges at the edge of the exposed graphite part, and this raised part is chipped off during the polishing process.This chipped part is comparable to the thinning of the graphite caused by the nitriding process, and the graphite and base metal are separated. Creates a fJJK gap with the part. This gap also becomes an oil pocket in the Ganolin Ennon, which can be expected to produce better results, but in a diesel engine, the fuel contains a large amount of sulfur, which causes corrosion.

For sealing surface defects in general cast iron products,
Although it is known to impregnate hydraulic glass, etc., this method cannot be used for engine cylinders that require heat resistance and 1 friction AL properties.

The object of the present invention is to improve corrosion resistance, especially corrosion and abrasion resistance.
The purpose of the present invention is to provide nitrided cast iron products and methods of manufacturing the same.

5. The nitrided cast iron product of the present invention has a nitrided layer on the surface. The table I/
Ij(rc) is characterized in that the gap in the matrix part 7 around the exposed graphite is sealed with a resin mixed with a sacrificial corrosion metal that causes sacrificial corrosion to the matrix part.

This method for manufacturing nitrided cast iron products involves nitriding the surface of a cast iron material, grinding the nitrided surface, and mixing a sacrificial corrosion metal that causes sacrificial corrosion to the base material into the ground surface. ζ Resin is applied, sacrificial corrosion metal and resin are rubbed into the gap between F and 4) J parts around the graphite exposed on the surface, and the heat-treated parts are used as flaw marks.

In the case of nitrided cast iron products made from wood ψj, a resin mixed with a sacrificial corrosion metal is embedded in the gap between the graphite and the fU radius formed on the surface during the nitriding process and subsequent grinding process. Therefore, the hardness of this nitrided cast iron product increases through nitriding treatment, and the surface wear resistance improves (1・l l
ji' (,) by resin containing sacrificial corrosion metal
Since the surface of the base material is no longer exposed, the corrosion resistance of the surface of the base material is reduced. '
l”]”JC%The sacrificial corrosion metal contained in this resin has the effect of preserving the cast iron base material through sacrificial corrosion action V.
Corrosion resistance can be improved compared to sealing with only oil. This sacrificial corrosion metal is preferably AL, Zn.
Either of these is mixed into the resin in a range of 5 to 80 volumes and 11 J. The reason for limiting the mixing amount is that if it is less than 5%, a sufficient sacrificial corrosion effect cannot be expected, and if it is more than 80%, the viscosity becomes high and coating is difficult, and at the same time, the adhesion of At and Zn metal powders is insufficient. This is because the puncture holes become awkward. It is appropriate to use a metal powder with a diameter of 200 mm or less (74μ).

The reason for this is that if the particle size is larger than this, it becomes difficult to enter the gap between the parent part and the parent part. Therefore, the nitrided cast iron product of the present invention, which has improved corrosion and wear resistance, can be used in the 7-rings of diesel engines that use highly corrosive fuel. After removing the protruding layer on the surface of VJ iron products by grinding, a sacrificial metal-containing resin is applied.
After drying, it is subjected to a rubbing process such as wrapping, followed by heat treatment, and has a sufficient pore-sealing effect.

That is, it is possible to obtain a nitrided cast iron product with improved corrosion resistance by a relatively simple method.

Preferred basic properties of the resin used in the present invention are as follows.

(1) Will not be altered by combustion such as solin or light oil, sulfuric acid, oil, or water.

(2) No thermal decomposition occurs at 250°C.

(3) ′! :'; Easy to apply with Wt.

What is an example of a resin that satisfies these conditions? Kino resin, phenol resin, polyimide resin 1. lゝ゛1 Noah
Mi 1st month, 7th birthday
There are two types: one for the meadow tree and the other for the fluorine tree.

In a preferred embodiment of the side hole treatment using this resin, after removing the protrusions on the surface of the graphite matrix produced by the nitriding treatment by grinding, a resin containing a sacrificial corrosion metal is applied, and then dried. Afterwards, rub the resin with 1/c7IL2 or more of 11 nickel for 0.5 hours, and rub the resin for 1 time in the range of 100 to 400℃ for 0.5 hours or more at the appropriate temperature in the atmosphere. The stirrups are processed.

The reason for limiting the temperature of this heat treatment is that if it is less than 100°C, the resin will not harden sufficiently and the ILF will not have a sufficient sealing effect, and if it exceeds 400°C, the nitrided cast iron will decompose. This is a 2-1 event in which the number of players, face j, and fL decreases. Table 1 shows the relationship between each resin and its preferable heating rate of 1+'2'.
1350℃ As the nitriding treatment, gas nitriding, ion nitriding, force soft nitriding, tuftride, etc. can be used, and Ennon's 7
When performing gas nitrocarburizing treatment for ring liners,
In order to prevent deformation, it is preferable to carry out the test under the conditions of 550 to 600°C, 30 minutes to 30 hours.

0.2%Cr, 0.7%Cu, 0-065
%Sn.

A flaky graphite alloy cast iron having a composition of residual Fe was melted, cast, cut, and ground to form a cylindrical sample (inner diameter 39 mm).
mm + outer diameter 98 mm, length 160 nun)
K made/this. Next, this sample was heated at 570°C for 3 hours for 5 hours.
Soft nitriding treatment was performed under the conditions of 0% RX/50% N1-13. At this time, a compound layer 10 with nitrogen is formed on the surface of the cast iron product, as schematically shown in FIG.
At the same time, a bulge occurs in the graphite portion 12, which is the composition of the cast iron product. Further, since the graphite 12 is thinner, a gap is formed between the graphite 12 and the base material 14. Next, the protrusions on the surface of the nitrided cast iron product are removed by honing to create a smooth surface as shown in Figure 2.

Then, apply epoxy/resin containing a sacrificial corrosion metal at a certain ratio to this table IR1 (as shown in Figure 3), and after drying the resin layer 15, grind it with a ruby grindstone at a pressure of 1 to 2/(:1 rL). The resin portion 16 has a sealing effect on the exposed portion of the graphite 12 as shown in FIG. 4. As shown in FIG.

Microscopic photographs of the electrified pJ iron crystal surface obtained by the method of the present invention are shown in FIGS. 5 to 8.

In this case, the resin used in the sealing treatment θ has an At of 60
Evokin resin containing % by weight.

In Figure 5, the black part indicates the sealing part. Figure 6 is ×
Line f shows only the Fe component on the surface, and the white dots are the Fe component.

In FIG. 7, only the At component on the surface is imaged using X-rays, and the At component is dotted in white. By comparing with FIGS. 5 and 6, it can be seen that At 2 exists in the sealing portion.

In Figure 8, the black portion is 1? It is a resin, and the white dots in it are At.

Next, the samples prepared according to the method V described above were subjected to a trial test without sealing.

The samples tested are shown in Table 2.

Table 2: Sample 8 j Epoxy containing 5% At powder 1 □ Gas soft nitriding with resin sealing treatment ::' 7 Gas soft nitriding with resin sealing treatment :: Chemical cast iron product i aI sealing with fat Hole-treated gas V (nitrided i/cast iron product □1-1--------1-
: ! Sample EIZn Epoxy containing 80i amount% of powder 1
A basic dry abrasion test test apparatus 6' is shown schematically in FIG. 9.

The specimen 20, which has been nitrided and sealed in the above manner, is fixed on the base 22 installed on the floor +Tjj 18 with its treated surface turned upside down.

(7) The Ic piece 20 is cut out from a cylindrical sample formed in the shape of Entsuno's 7-ring inner. This specimen 20 is, for example, fi] 1' 5 nnnz length 75 mm and has a bolt hole drilled in it. le 1
・It is fixed to the base with etc. On the two sides of this specimen, there is a contact gIS cut out from a part of Ennon's piston ring.
When the contact part 24 is in contact with the holder 2, this contact part 24 is connected to the holder 2.
It is held at 6. This holder is attached to the tip of an arm 28, which connects the connecting member 30.
It is connected to a motor 34 via 32. The supporting points 36, 38, and 40 of the connecting member are all rotatable, and the rotational motion of the motor 34 is transmitted as a reciprocating motion of the holder 26, and the contact portion 24 slides on the upper surface of the specimen 20. A predetermined cart P can be hung on this holder in the direction of the arrow in the figure.
A certain surface pressure is generated between the specimen 20 and the specimen 20.

The main conditions of the test are as follows: Friction speed in atmosphere: Near 00cycles/min Number of frictions: 2x10cycles P: 1.2-20k11 IJE: 0, 4kg/min
mm Sliding width: 10 m1n Wear blur measurement method: Mold breaking method Note that in order to accelerate wear, 10% diesel oil and 11% water were added to the engine oil between the contact hole 24 and the specimen 20. ．．
0%, H2S0 and 45% were added, and a corrosive lubricant was used. The results are shown in FIG.

The lower graph shows the amount of wear on the mating material, that is, the contact member 24. According to this result, the wear of the test needle 4s, c, o, E according to the invention! - indicates that the wear and melting of both the sample and the mating material is reduced compared to the conventional sample.

(2) Local test The corrosion of the inner wall of the diesel engine ring was caused by H2S.
Presuming that it was caused by O4-based VC, the specimen was immersed in sulfuric acid water for a certain period of time, and the amount of weight loss was measured.

Test, test conditions Immersion II &: 1 vow, % H2S O4 aqueous solution Temperature: Room temperature Time: 8 hours Samples: 6 each The test results are shown in FIG.

In this round, the corrosion loss per 1-11 hours was 1 c of sample.
In the figure, A, B, C, D, E are the same as in FIG. 10. In this test, the weight loss of samples B, C, D, and H according to the present invention was smaller than that of conventional sample A.

[Brief explanation of the drawing]

Figure 1 is an enlarged partial cross-section schematically showing the cross-section of the cast iron product after nitriding treatment, and Figure 2 is the cross-section of the cast iron product shown in Figure 1 after the surface protrusions have been removed. Figures 6 and 4M, which are similar to '1', show the first part after the pores have been sealed with resin.
Figures similar to the above figure, Figures 1 and 5 are electron micrographs at a magnification of 400 of the metal structure of the surface of the nitrided cast iron product according to the present invention that has undergone sealing treatment, and Figures 6 and 7 are photographs of the metal structure of the surface of the nitrided cast iron product according to the present invention that has been sealed. An X-ray photograph of the metal structure of the surface of the nitrided cast iron product according to the present invention, FIG.
Magnification of metal structure on the surface of nitrided cast iron product according to the present invention: 400
FIG. 9 is a schematic diagram of the wear test device, FIG. 10 is a graph showing the results of the wear test, and FIG. 11 is a graph showing the results of the corrosion test. Explanation of symbols 10 Compound layer, 12...graphite, 14...base material part, 2
0 ・Test piece, 24... Contact member, 34... Motor 〇3
68 (X400) (λ400) (84Llυ) Procedural Amendment. Showa month Ell, r l-
i'l' +3 Director Kazuo Wakasugi
Title 2 Title of the invention Nitrided cast iron product and its manufacturing method:
) Relationship with the case of the person who cheated on the arrest Applicant name (313) Toyo Kogyo Co., Ltd. 4, Agent 7 Supplement 11 Subject d°″' in I1 of the detailed explanation of the invention in Akira I .゛““゛”
Doman]〉\(1) 1 ya) ηSK Negative 130 weight - Ha 4?61 of the evening line is corrected to "30 volume' - 11%". (2) Table 2 on the first page of Book IV is corrected as follows. "Table 2

Claims (2)

[Claims] (1) The surface has a nitrided layer, and the gap between the graphite exposed on the surface and the surrounding f1 part is punctured with a resin mixed with a sacrificial corrosion metal that causes sacrificial corrosion to the base material. A nitrided cast iron product featuring: (2) Nitriding the surface of the cast iron material, grinding the nitrided surface, coating the ground surface with a resin mixed with a sacrificial corrosion metal that causes sacrificial corrosion to the base material, and sacrificial A method for manufacturing a nitrided cast iron product, characterized by rubbing corroded metal and resin into the gap on the base material around the graphite whose surface has been exposed to KN, and heat-treating the product.