CN1184360C

CN1184360C - Anti-corrosion process for pure iron

Info

Publication number: CN1184360C
Application number: CNB021285195A
Authority: CN
Inventors: 赵瑞清
Original assignee: Institute of Electronics of CAS
Current assignee: Institute of Electronics of CAS
Priority date: 2002-08-09
Filing date: 2002-08-09
Publication date: 2005-01-12
Anticipated expiration: 2022-08-09
Also published as: CN1473964A

Abstract

The present invention relates to an anti-corrosion process for pure iron. The surface of the pure iron is cleaned, wherein the pure iron has smooth surface, no hole and no rough scratch on edges. The surface of the pure iron is plated with one layer of metallic nickel of 20 to 25 mu m by a direct current. In a hydrogen furnace, after temperature is heated to 800 DEG C, the pure iron is heated to reach the temperature from 920 to 930 DEG C at the speed of 50 to 80 DEG C per hour, and the temperature is kept for 3 to 5 hours. After the pure iron is cooled to each the temperature from 700 DEG C at the speed of 50 to 80 DEG C, the temperature of the pure iron is cooled to the room temperature along with furnace temperature. A processed pure iron part has good surfaces and has no corrosion phenomena after being used for a long time.

Description

A kind of anti-corrosion process for pure iron

Technical field

The present invention relates to a kind of anti-corrosion of metal technology.

Background technology

In the design of electron tube, the pure iron material is use always in the magnetic Circuit Design a kind of.The leading indicator of selecting this material for use is the requirement that high magnetic permeability (μ m) and saturation induction density (Bs) value can satisfy permanent magnet focusing system in the electron tube, in addition cause the pure iron material to need long-term contact cooling water or anti-freeze cooling liquid etc. in order to satisfy the heat conduction requirement in some high power device, so very easily form the corrosion of pure iron material, water coolant (liquid) jaundice, can cause device gas leakage when serious.And at present Bs, the requirement of μ m value that can satisfy pure iron do not arranged as yet, can satisfy the pure iron of not embroidering of the requirement of corrosion resistance again.Therefore, the normal method that adopts of people is at ferrous metal outside plating one deck nickel, but this coating very easily peels off, and does not satisfy above-mentioned requirements.

Summary of the invention

The object of the present invention is to provide a kind of anti-corrosion process for pure iron, can prevent effectively that corrosion phenomena from appearring in the magnetic circuit element that the pure iron material is made.

The present invention is used to realize that above-mentioned technical scheme is based on following principle.

Iron is the metal with high magnetic permeability and saturation induction density value, has two kinds of isomers under solid-state: α iron (body-centered cubic) and γ iron (face-centered cubic).α iron can exist in two temperature ranges, promptly is lower than 911 ℃ and existence between 1392 ℃-1539 ℃.And 911-1392 ℃ temperature range, iron atom is that face-centered cubic is arranged, and has lower free energy, so generation α → γ is deformed into γ iron mutually when be heated to 911 ℃; At ambient temperature, the lattice parameter of carbon-free α-Fe is 2.86 dusts (), and the lattice parameter of carbon-free γ-Fe is 3.56 dusts (950 ℃ time γ-Fe lattice parameter be 3.656 dusts).Need to prove that γ-Fe lattice parameter is determined with extrapotation during owing to room temperature, so be approximation.

Nickel is the stronger metal of erosion resistance, and its molten point is 1452 ℃, and proportion is 8.907, and lattice is a face-centered cubic lattice, and lattice parameter is 3.54 dusts.

Above-mentioned data show to have identical face-centered cubic lattice lattice between γ → Fe and the Ni, and both lattice parameters are very approaching.

Nickel layer can make the bonding force of coating be improved through heat-treated.And thermal treatment temp is higher, and is more favourable to the bonding force of improving coating and matrix metal.When thermal treatment temp reaches certain temperature, very thin diffusion layer has appearred on the line of delimitation of coating and matrix metal, this diffusion layer is the iron nickel alloy layer, between γ-Fe and Ni, form the solid solution alloy of a series of face-centred cubic structures continuously, the bonding force of nickel dam and matrix metal is strengthened.This diffusion layer has extremely strong erosion resistance, pure iron is played the effect of protective barrier.See also Fig. 1, this figure is iron-nickel binary alloy phase diagram.

In the iron nickel alloy layer, the content of nickel directly influences its structure body and forms, and for low Ni alloy, it is the same with α iron to be body-centered cubic structure; Nickel content is face-centred cubic structure as nickel just greater than 30%, is containing the mixing phase region of 10-30% nickel, and the pyritous face-centered cubic can be transformed into body-centered cubic lattice in the mode of martensite type phase transformation when cooling; This phase transformation is irreversible, and promptly Xiang Bian And does not take place on same temperature when heating and cooling.

Concrete technical scheme of the present invention is at pure iron surface dc plating one deck 20-25 μ m metallic nickel, be warming up in the hydrogen furnace that the speed with 50-80 ℃/hour is warming up to 920-930 ℃ after 800 ℃, be incubated 3-5 hour, be cooled to room temperature with furnace temperature after being cooled to 700 ℃ with 50-80 ℃/hour speed.

Description of drawings

Fig. 1 a and Fig. 1 b are binary alloy state graph Fe-Ni phasor.

Fig. 2 amplifies 100 times stereoscan photograph for Fe-Ni alloy plated layer of the present invention.

Fig. 3 is Fe-Ni alloy plated layer energy-spectrum scanning figure of the present invention, and wherein Fig. 3 a is the curve of iron, and Fig. 3 b is the curve of nickel.

Fig. 4 is that the Fe-Ni alloy interface Ni of place one side of the present invention can spectrogram.

Fig. 5 is that the Fe-Ni alloy interface Fe of place one side of the present invention can spectrogram.

Embodiment

By following embodiment that exemplifies and comparative example, can more be expressly understood content of the present invention.

Embodiment 1

Select smooth surface for use, N/D, no hole, edge do not have the pure iron of coarse cut and make test wrapper, clean surface, direct current nickel plating.The plating nickel on surface layer is unique source of nickel in the alloy, that is the number of Ni content depends on the thickness of surface plating Ni layer, the thick 25 μ m of this routine coating entirely at Fe-Ni circle and in the thermal diffusion layer that layer forms.When heat-treating in the hydrogen furnace, need to consider heat treated temperature because the part in the magnetic loop needs Yong Palladium silver-copper brazing alloy (890-900 ℃) and silver-copper brazing alloy (779 ℃) soldering, so thermal treatment temp should to be higher than above two temperatures more suitable.Be warming up to 800 ℃ in this example earlier, be warming up to 920 ℃ of temperature with 60 ℃/hour speed then, be incubated 4 hours.Pure iron owing to there is stress, can make magnetic property reduce, in order to eliminate stress and to improve magnetic property, the thermal treatment of must annealing after being processed into magnetics.Therefore in this example again the speed with 60 ℃/hour be cooled to 700 ℃, be cooled to room temperature with stove then.

Part after the processing is soaked in to reach in the cooling fluid in the water and carries out corrosion test, and cooling fluid is the mixing solutions of weight ratio 56% cooling circulating water and 44% deicing fluid.When observing the piece surface state every day, in atmosphere, expose approximately about half an hour, be soaked into again in the solution, to show that it is not only in solution but also be state in atmosphere.Through the observation more than 2 years, piece surface is still intact, does not have corrosion phenomena.

Comparative example 1

Press embodiment 1 condition, changing direct current nickel plating is double-pulse plating nickel, the thick 10 μ m of coating.Find that promptly part edge has an aperture by corrosion after soaking a week.

Comparative example 2

Press embodiment 1 condition, the nickel plating bed thickness is 20 μ m, is warmed to 800 ℃ in the hydrogen furnace, is incubated 1 hour, takes out after being cooled to room temperature with stove then, is immersed in the aqueous solution, and by soaking totally 27 days, the corrosion hole appears in part edge.

Comparative example 3

Two pulse nickel plating, the thick 10 μ m of coating directly soak in the entry without pyroprocessing, and after 36 hours, 2-3 place, corrosion hole appears in part edge, increases successively again later on to 5-6 corrosion hole point, and class appearance of yellow rust is arranged.

Test result

The part of embodiment 1 preparation being cut, get its section polishing and make the test standard specimen, is to observe the cross section pattern under the 1.3KX situation making energy-spectrum scanning and enlargement ratio on the scanning electron microscope.Its cross-section morphology as shown in Figure 2, energy-spectrum scanning figure is as shown in Figure 3.By the energy-spectrum scanning curve as can be known, the Fe-Ni diffusion layer expands mutually all right, and in the Ni at Fe-Ni interface one side, Ni content about about 80% (Wt%) Fe content is about about 20%, and in Fe one side, Fe content 98% and Ni content is about 1.7%.And in the middle part of Fe-Ni diffusion layer, the content of Fe and Ni is close to and respectively accounts for half, and the diffusion layer degree of depth reaches about 200 μ m, referring to accompanying drawing 4 and Fig. 5.Wherein the test condition of Fig. 4 gained curve is: acceleration voltage 20KeV, and working lipe, initial angle was 12.54 °, 10 ° at inclination angle, 60 seconds working lipe, retardation time 14.047, superposition number of times 4 times records weight ratio Fe-K=20.67%, Ni-K=79.33%.The test condition of Fig. 5 gained curve is: acceleration voltage 20KeV, and working lipe, initial angle was 12.54 °, 10 ° at inclination angle, 46 seconds working lipe, retardation time 10.698, superposition number of times 3 times records weight ratio Fe-K=98.28%, Ni-K=1.72%.

Claims

1, a kind of anti-corrosion process for pure iron, it is characterized in that pure iron surface plating one deck 20-25 μ m metallic nickel is warming up in the hydrogen furnace that the speed with 50-80 ℃/hour is warming up to 920-930 ℃ after 800 ℃, be incubated 3-5 hour, be cooled to 700 ℃ of postcooling to room temperature with 50-80 ℃/hour speed.

2, anticorrosion process as claimed in claim 1 is characterized in that, described coating is direct current electrode position.

3, anticorrosion process as claimed in claim 1 is characterized in that, described pure iron smooth surface.

4, anticorrosion process as claimed in claim 1 is characterized in that, nickel plating after the described pure iron clean surface.