WO1992021793A1

WO1992021793A1 - Process for surface treatment of tools for chip removal

Info

Publication number: WO1992021793A1
Application number: PCT/EP1991/002213
Authority: WO
Inventors: Pietro Fiori
Original assignee: Pietro Fiori
Priority date: 1991-06-07
Filing date: 1991-11-25
Publication date: 1992-12-10
Also published as: IT1245874B; AU8914891A; ITRM910399A0; ITRM910399A1

Abstract

The process relates to surface treatment of a tool by chip removal and comprises the following phases: (a) predegreasing, (b) pickling, (c) electrolytic degreasing, (d) acid neutralization, (e) nickel-plating, (f) electrogalvanic deposit of a layer of metal of high surface hardness and low friction coefficient, (g) dehydrogenation. A tool thus treated has a low friction coefficient, proving to be suitable particularly for working copper, aluminum or metals with similar characteristics. Its average life is increased more than three times and its cost is only doubled.

Description

Process for surface treatment of tools for chip removal

The invention relates to the field of tools for chip removal mechanical working such as turning, reaming, drilling, cutting and the like.

As is known, two of the most important aspects for the definition of the quality of a tool are work precision and life.

Particularly in regard to life, the most advantageous results are now obtained by using tools (or rather only applied cutting edges) of high surface hardness, made, for example, of tungsten carbide instead of steel.

Other conditions being the same, this solution allows an increase of the average life of a tool equal to about five times, but comprising as an offset an increase of 10-12 times the cost of the tool itself.

But in regard to efficiency and precision of the tool during various workings, the above-described solution does not obtain considerable results for cycles of working pieces of aluminum, copper or metals having similar physical characteristics.

Such metals, together with a relatively high friction

coefficient, exhibit a low strain strength under compressive conditions.

In many cases, because of certain cutting and advancing speeds, the chips are not removed correctly from the cutting zone and, being deformed by compression, are wedged between the tool and the surface of the piece, inevitably causing working imprecision and, often, even breaking of the tool. The applicant has aimed at providing a solution to this set of problems, conceiving a process for surface treatment of said tools which comprises an increase of the life and a better dependability, especially in the case of working of metals such as copper and aluminum, but without comprising for the tools in question cost increases on the order cited above.

Actually the treatment conceived by him guarantees an increase of the life of a tool equal to more than 3 times, comprising cost increases equal to only twice with respect to a standard steel tool.

The object of the invention is a process of surface treatment of tools chip removal mechanical working to increase the surface hardness and reduce its friction coefficient, characterized by the fact of comprising the following phases:

a) predegreasing

b) pickling

c) electrolytic degreasing

d) acid neutralization

e) nickel-plating

f) electogalvanic deposit of a layer of metal of high surface hardness and low friction coefficient

g) dehydrogenation.

Tools obtained by performing said process also come within the object of the invention.

In an embodiment preferred by the inventor, and therefore not limiting or binding, the process provides that the outside

coating metal galvanically deposited in phase f) of the process is chromium, which exhibits the characteristics of a high surface hardness and a low friction coefficient.

In the preferred embodiment, the characteristic procedures of the process are the following: a) the predegreasing is performed by immersion in a sodium hydroxide solution at a temperature of 60-70°C for about 5 minutes;

b) the pickling is performed by immersion in a hydrochloric acid solution at a temperature of 20-30°C for about 1 minute;

c) the electrolytic degreasing is obtained by galvanic treatment in a sodium hydroxide solution, sequestering and complexing agents at a temperature of 20-30°C for about 3 minutes.

d) acid neutralization is performed by galvanic treatment in sulfuric acid solution at a temperature of 20-30°C for a period of 10-12 seconds with the piece connected to the cathode.

e) the nickel-plating is performed electrolytically by galvanic treatment in a solution of nickel salts at a temperature of 20- 30°C for a sufficient period for there to be deposited on the surface of the piece a nickel layer of a thickness at least equal to about 2.10^-4 mm.

f) the chrome-plating is performed by galvanic treatment in a solution of chromic acid, sulfuric acid with catalysts such as sulfate ions or rare earth fluorides at a temperature of 50-60°C with a current density between 3A/dm² and 60A/dm² for a

sufficient period for there to be deposited on the surface of the piece a chromium layer with a thickness between 5.10^-4 and 5.10^-3 mm.

The surface hardness obtained with the process described is about 1200 HV 0.1.

The tools treated according to the process of the invention constitute an economically and technologically valid solution of the problems set forth during this description, and therefore achieve the object proposed by the applications.

of course the process of the invention according to the preferred embodiment can be modified in its characteristic parameters, as also in the type of catalysts, depending on the particular requirements of the tools to be treated, but remaining Within what has been stated in claim 1.

For example, a possible variant of the process provides that phase e) of nickel-plating is substituted by a phase called

"anode etching," by inducing a corrosion by the anode current of the tool itself immersed in a chromium bath for a period of 2-10 seconds. Thus, a perform adherence is obtained of the chromium which is deposited on the treated tool.

But another variant provides that the phase e) of nickel-plating is performed by a chemical process, by treating the tool with nickel salts and reducing agents, for example, sodium

hypophosphite. The working temperature is 85°C-90°C, a deposit of about 0.2-0.5 mm is obtained.

Claims

1. Process of surface treatment of tools chip removal mechanical working to increase the surface hardness and reduce its friction coefficient, characterized by the fact of comprising the

following phases:

a) predegreasing

b) pickling

c) electrolytic degreasing

d) acid neutralization

e) nickel-plating

g) dehydrogenation.

2. Process according to claim 1 wherein the metal of high hardness and low friction coefficient cited in phase f) is chromium.

3. Process according to claim 2, wherein:

a) the predegreasing is performed by immersion in a sodium hydroxide solution at a temperature of 60-70°C for about 5

minutes;

e) the nickel-plating is performed electrolytically by galvanic treatment in a solution of nickel salts at a temperature of 20-30°C for a sufficient period for there to be deposited on the surface of the piece a nickel layer of a thickness at least equal to about 2.10 ^-4 mm.

f) the chrome-plating is performed by galvanic treatment in a solution of chromic acid, sulfuric acid with catalysts such as sulfate or fluoride ions of rare earths at a temperature of 50- 60°C with a current density between 3A/dm² and 60A/dm² for a sufficient period for there to be deposited on the surface of the piece a chromium layer with a thickness between 5.10^-4 and 5.10^-3 mm.

4. Process according to claim 3, wherein phase e) of nickel-plating is substituted by a phase called "anode etching," in a chromium bath for a period of 2-10 seconds.

5. Process according to claim 3, in which phase e) of nickel-plating is performed by a chemical process with nickel salts and reducing agents, as sodium hypophosphite at a temperature of 85-90°C.

6. Tools for surface-treated chip removal mechanical working with the process according to any of the above claims.