GB1581345A - Method of hot-forging with waterbased lubricant - Google Patents

Description

(54) METHOD OF HOT-FORGING WITH WATER-BASED LUBRICANT (71) We, THE BRITISH PETROLEUM COMPANY LIMITED, of Britannic House, Moor Lane, London, EC2Y 9BU, a British Company, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to a method of hot forging with water-based hot forging lubricants.

In the production of certain products for the automotive industry e.g. crankshafts, spiders for universal joints, a rough forging is initially produced which is subsequently further precision machined. It is necessary initially to coat the die for use in the process with a hot forging lubricant.

Lubricants which have previously been used in the hot forging of ferrous metal are mineral oil (Stampers Oil), graphite/water and graphite/oil. The use of mineral oil in hot forging lubricants is undesirable as the fumes produced by the contact of oil with a die at high temperature constitute a health hazard. Grahite containing hot forging lubricants also have certain disadvantages which include inferior friction characreristics at the high temperature of hot forging and deposit build up with the dies.

The present invention relates to a method of hot forging in which the lubricant which is water-based reduces the environmental and safety problems associated with conventional hot forging lubricants.

Thus according to the present invention, there is provided a method of hot forging of ferrous or non-ferrous metals in which a die is coated with a hot forging lubricant comprising 60 to 99% by weight of water, 1 to 40% of a mono-ester, di-ester or tri-ester of a poly-hydric- alcohol or 1 to 40% of a mixture of said esters, and an emulsifier which is the product of the reaction of lauric acid and triethanolamine, prior to the metal being introduced to the die.

The term polyhydric alcohol is intended to refer to an alcohol having 3 or more hydroxyl groups.

Preferably the polyhydric alcohol is a tetrahydric alcohol. The preferred alcohol being pentraerythritol. Other suitable polyhydric alcohols include trimethylolpropane and glycerol.

Preferably the ester is a mon-ester or di-ester of a C1() to C,() carboxylic acid, most preferably a mono-carboxylic acid such as lauric, stearic acid, or oleic acid.

It is further advantageous to incorporate an agent in the formulation such as talc, borax or sodium metasilicate to aid in releasing a workpiece from the die. Further a wetting agent may be included in the fluid formulation such as an ethoxylated nonyl phenol.

A preferred formulation comprises roughly equal proportions of a mono-ester and di-ester of a polyhydric alcohol, most preferably comprising 3 to 10% of the mono-ester and 3 to 10% of the di-ester. The most preferred formulation comprises 3 to 10% of pentraerythritol monostearate and 3 to 10% of pentaerythritol distearate.

The invention will now be described by way of example only with reference to the Table and Figures 1 to 3 of the accompanying drawings.

Figure 1 shows the results of the wetting tests of the blends (1-5) shown in the Table.

Figure 2 shows the friction test results of said blends (1-5) and Figure 3 shows the blend 'life' obtained from a simulated friction tester.

TABLE HOT FORGING LUBRICANTS FORMULATION BLEND1 2 3 4 5 6 Water % wt90.5 88.0 87.0 88.0 88.0 76 Lauric acid % wt 1.0 1.0 1.0 1.0 1.0 2.0 Triethanolamine % wt 0.5 0.5 0.5 0.5 0.5 1.0 Pentaerythritol Monostearate % wt 4.0 5.0 5.0 5.0 5.0 10.0 Pentaerythritol distearate % wt 4.0 5.0 5.0 5.0 5.0 10.0 Talc % wt - 0.5 0.5 - 0.25 0.5 Ehtoxylated nonylphenol % wt - - 1.0 - - - Borax (Sodium tetraborate) % wt - - - 0.5 0 5 Sodium metasilicate % wt - - - - 0.25 0.5 The wetting tests of Figure 1 are a measure of the area covered by the formulations at a 10:1 dilution in water, preferably deionised, when sprayed from a hand spray gun as used for conventional oil-based forging lubricants from a position 12 inches from a 6" x 4" mild steel plate held at 60 to the vertical. Also marked on the graph are the results for a graphite/water mix (G) and mineral oil (Stampers Oil).

It is desirable that the lubricant covers the entire die surface during the hot forging process and a lubricant is more effective the greater its wettability at a given temperature.

The main practical area of interest is between the temperature range 250 to 4500. The results show that the formulations are generally better than the graphite with blend 5 the best. The blends used are not as effective as oil but oil has serious environmental objections due to fuming.

The frictional properties of the formulations are shown in Figure 2. Good frictional properties are desirable for a lubricant mainly between 350" and 500"C with an ability to lubricate at temperatures up to 600"C for limited periods. This allows hot material to flow through the die without sticking. The blend results show that a relatively constant friction coefficient is obtained over a wide temperature range (similar to oil) while the graphited product shows variations.

The results for lubricant life before scuffing (shown in Figure 3) were obtained on a simulated friction tester. The test was carried out in a manner similar to that for the Four Ball Test (a procedure well known in industry for testing the characteristics of lubricating oils) except that the lower three balls are replaced by pins. The time required before scuffing failure to occur using a particular formulation was noted for various temperatures.

Figure 3 indicates that the formulations 1-5 have less tendency than the (G) formulation to vary life with change of temperature.

Although dilution of the lubricant up to a level of 10:1 with water resulted in an initially unstable mix, subsequent agitation produces mixtures which were found to be stable and sediment free for at least 10 days.

WHAT WE CLAIM IS: 1. A method of hot forging of ferrous or non-ferrous metals in which a die is coated with a hot forging lubricant comprising 60 to 99fro by weight of water, 1 to 40% of a mono-ester, di-ester or tri-ester of a polyhydric alcohol or 1 to 40% of a mixture of said esters, and an emulsifier which is the product of the reaction of lauric acid and triethanolamine, prior to the metal being introduced to the die.

2. A method according to claim 1 in the polyhydric alcohol is tetrahydric alcohol.

3. A method according to claim 2 in which the tetrahydric alcohol is pentaerythritol.

4. A method according to claim 1 in which the ester is a mono-ester, di-ester or tri-ester of a C,, to C2(, carboxylic acid.

5. A method according to claim 4 in which the C", to C2( carboxylic acid is stearic acid.

6. A method according to claim 5 in which the hot forging lubricant comprises 3 to 10% by weight of pentaerythritol monostearate and 3 to 10% by weight of pentaerythritol distearate.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. TABLE HOT FORGING LUBRICANTS FORMULATION BLEND1 2 3 4 5 6 Water % wt90.5 88.0 87.0 88.0 88.0 76 Lauric acid % wt 1.0 1.0 1.0 1.0 1.0 2.0 Triethanolamine % wt 0.5 0.5 0.5 0.5 0.5 1.0 Pentaerythritol Monostearate % wt 4.0 5.0 5.0 5.0 5.0 10.0 Pentaerythritol distearate % wt 4.0 5.0 5.0 5.0 5.0 10.0 Talc % wt - 0.5 0.5 - 0.25 0.5 Ehtoxylated nonylphenol % wt - - 1.0 - - - Borax (Sodium tetraborate) % wt - - - 0.5 0 5 Sodium metasilicate % wt - - - - 0.25 0.5 The wetting tests of Figure 1 are a measure of the area covered by the formulations at a 10:1 dilution in water, preferably deionised, when sprayed from a hand spray gun as used for conventional oil-based forging lubricants from a position 12 inches from a 6" x 4" mild steel plate held at 60 to the vertical. Also marked on the graph are the results for a graphite/water mix (G) and mineral oil (Stampers Oil). It is desirable that the lubricant covers the entire die surface during the hot forging process and a lubricant is more effective the greater its wettability at a given temperature. The main practical area of interest is between the temperature range 250 to 4500. The results show that the formulations are generally better than the graphite with blend 5 the best. The blends used are not as effective as oil but oil has serious environmental objections due to fuming. The frictional properties of the formulations are shown in Figure 2. Good frictional properties are desirable for a lubricant mainly between 350" and 500"C with an ability to lubricate at temperatures up to 600"C for limited periods. This allows hot material to flow through the die without sticking. The blend results show that a relatively constant friction coefficient is obtained over a wide temperature range (similar to oil) while the graphited product shows variations. The results for lubricant life before scuffing (shown in Figure 3) were obtained on a simulated friction tester. The test was carried out in a manner similar to that for the Four Ball Test (a procedure well known in industry for testing the characteristics of lubricating oils) except that the lower three balls are replaced by pins. The time required before scuffing failure to occur using a particular formulation was noted for various temperatures. Figure 3 indicates that the formulations 1-5 have less tendency than the (G) formulation to vary life with change of temperature. Although dilution of the lubricant up to a level of 10:1 with water resulted in an initially unstable mix, subsequent agitation produces mixtures which were found to be stable and sediment free for at least 10 days. WHAT WE CLAIM IS:

1. A method of hot forging of ferrous or non-ferrous metals in which a die is coated with a hot forging lubricant comprising 60 to 99fro by weight of water, 1 to 40% of a mono-ester, di-ester or tri-ester of a polyhydric alcohol or 1 to 40% of a mixture of said esters, and an emulsifier which is the product of the reaction of lauric acid and triethanolamine, prior to the metal being introduced to the die.

2. A method according to claim 1 in the polyhydric alcohol is tetrahydric alcohol.

3. A method according to claim 2 in which the tetrahydric alcohol is pentaerythritol.

4. A method according to claim 1 in which the ester is a mono-ester, di-ester or tri-ester of a C,, to C2(, carboxylic acid.

5. A method according to claim 4 in which the C", to C2( carboxylic acid is stearic acid.

6. A method according to claim 5 in which the hot forging lubricant comprises 3 to 10% by weight of pentaerythritol monostearate and 3 to 10% by weight of pentaerythritol distearate.

7. A method according to any of the preceding claims in which the hot forging lubricant

also comprises a release agent consisting of talc, borax, sodium meta-silicate or a mixture of two or more of said agents.