DE102007045820A1 - Improved lubricant formulation for metal forming processes at elevated temperatures - Google Patents

Abstract

Improved lubricant system useful in metal forming processes. The lubricant formulations contain a boron nitride lubricant with graphite additives. These formulations improve lubricity while maintaining good adhesion at elevated temperatures.

Description

Technical area

The The present invention relates generally to lubricant formulations. the for Metal forming process at elevated Temperatures such. B fast plastic forming, superplastic Forming and hot forming process are useful.

Background of the invention

The Development of lubricants for Metal forming process at elevated Temperatures such. B. rapid plastic forming (qick plastic forming = QPF), superplastic forming (SPF) or Hot forming requires the following features: a low coefficient of friction, good adhesion to the blank, a uniform application pattern, low Cost and easy removal after forming. lubricant On a petrochemical basis are due in this process used high temperatures ineffective. The most common used lubricant for Procedures that increased such Temperatures include boron nitride (BN). There were, however, too other lubricants, such as. As graphite, molybdenum disulfide and magnesium hydroxide (in aqueous Suspension often used as Magnesia Milk).

Summary of the invention

The Invention is intended to advantages and alternatives over embodiments of the prior Provide technology by providing improved lubricant formulations which are useful in metal forming processes at elevated temperatures. The formulations contain a boron nitride lubricant with graphite additives. These Formulations improve the lubricity while adhering well the surface of the blank is preserved.

Brief description of the drawings

The accompanying drawings, which are included in this description and form part of it, illustrate an exemplary embodiment of the invention, together with the above general Description and detailed description set forth below serves to explain the principles of the invention, wherein:

1 illustrates a cross-sectional view of a metal blank and die and punch forming tools prior to metal forming;

2 illustrates a cross-sectional view of a metal blank and die and punch forming tools during metal forming;

3 Fig. 12 illustrates a cross-sectional view of a metal blank and die and punch forming tools after completion of metal forming;

4 Figure 12 illustrates a cross-sectional view of a metal blank and die and punch forming tools after removal of the punch tool;

5 Fig. 12 illustrates a cross-sectional view of a metal blank and die and punch forming tools after removal of the deformed metal blank;

6 illustrates the effect of the graphite / boron nitride ratio on the coefficient of friction.

While embodiments of the invention illustrated above and generally described and in connection with certain of them, if any preferred procedures and designs should be described, should be understood and to be understood that the invention in no way refers to such embodiments and procedures illustrated and described herein can, limited should be. Rather, the present invention is intended to be directed to all Alternatives and variations that extend the far-reaching principles of the invention within the true spirit and scope thereof can.

Detailed description

To / m better reference and understanding is the following description with reference to a simplified exemplary metal forming method explained. It is important to understand that the lubrication system of the present invention by no means to such a shaping method limited is. It is rather considered pulled and it is intended that the lubrication system in wide To start with any number of metal forming processes at elevated Temperatures is applicable.

Reference will now be made to the various drawings in which like reference numerals designate like elements throughout the several views. The 1 - 5 12 schematically illustrate a simplified, exemplary, so-called "hot working" method using punch and die forming tooling elements In the illustrated method, a Ma trizenelement 12 a mold cavity 32 , a lower surface 14 and two opposite wall surfaces 16 , A metal blank 22 is placed on top of the die element so that a portion of the lower surface 30 of the metal blank 22 in direct contact with the outer surface 24 of the die element 12 stands.

1 shows the metal blank 22 in the position between the die element 12 and a complementary stamping tool 18 so the top surface 28 of the metal blank 22 to the stamp tool 18 has. Means (not shown) may be provided to both the stamping tool 18 as well as the metal blank 22 to heat to a suitable temperature. The stamp tool 18 is against the upper surface 28 of the metal blank 22 pressed. This process leads to the generation of an interface area 40 ( 2 ) between the punch tool 18 and the upper surface 28 of the metal blank 22 and causes deformation of the metal blank 22 so that it conforms to the shape of the mold cavity 32 of the die element 12 adapts.

As in 2 shown, deformed the pressure of the punch tool 18 on the upper surface 28 of the metal blank 22 acts, the metal blank down toward the lower surface 14 of the die element 12 ,

The lower surface 30 of the metal blank 22 stands with a section of the opposite wall surfaces 16 engaged, creating an interface area 38 between the die element 12 and the lower surface 30 of the metal blank 22 is produced. In 3 has the stamp tool 18 the lower surface 30 of the metal blank completely against the opposite walls 16 and the floor 14 of the die element 12 pressed. This further deformation creates a continuous interface area 38 between the die element 12 and the metal blank 22 and a continuous interface region 40 between the stamping tool 18 and the metal blank. After completing the forming process, the stamping tool becomes 18 from the engagement with the upper surface 28 of the metal blank 22 lifted ( 4 ) and the metal blank 22 gets out of the die element 12 away ( 5 ).

As will be appreciated by those skilled in the art, this is in the 1 - 5 Illustrated and described shaping methods only by way of example. Any number of other molding processes at elevated temperatures may also be used. By way of example only, and not limitation, various forming processes at elevated temperatures in the U.S. Patent 5,819,572 to Krajewski, the contents of which are hereby incorporated by reference in their entirety.

Independent of the molding process used is typically a certain type of lubrication during the metal forming process used. Lubrication is necessary to prevent sticking and thereby the deformation of the workpiece facilitate. Lubrication also serves to release the To assist the formed part of die and tool elements. The Lubricant can affect the area of the workpiece, which is subjected to deformation, and / or surfaces of the Mold design tools are applied.

The The present invention provides an improved lubrication system Use of a boron nitride (BN) lubricant with graphite additives to the lubricity to improve while a good adhesion to the metal blank and / or the tool elements, on which it is applied is preserved. In a possible preferred embodiment leads the Addition of at least 5% and more preferably about 5% to about 50% graphite to the boron nitride for improved lubricity (a lower coefficient of friction) in comparison with BN alone. in the Contrary to lubrication formulations consisting mainly of graphite, obtain the boron nitride-graphite formulations according to the invention good adhesion to the metal blank and mold tooling surfaces. It can be present in the lubricant, provided that that they do not have the characteristics of lubricity and adhesion significantly worsen.

According to the in consideration drawn procedures can the boron nitride-graphite formulations according to the invention using conventional Farbaufsprühverfahren can be sprayed on the metal blank or other workpiece and can help with standard procedures currently used for pure BN be removed. In a possibly preferred method the metal workpiece aluminum or magnesium, although equally used other workpiece materials can be. The boron nitride-graphite formulations according to the invention are as particularly suitable for Forming process considered at temperatures of about 250 degrees C or more become.

The major advantages in terms of lubricity achieved as a result of the addition of graphite are in 6 illustrated. In this graph, the coefficient of friction (RK) is measured for various values of graphite addition to boron nitride. The coefficient of friction was determined using a Cameron Plant test with a floating plate with a plate test procedure at 450 degrees C measured. The test was repeated at each graphite addition value to confirm relative performance.

As showed a standard boron nitride lubricant without added graphite (Columns far left) much higher values for the coefficient of friction as samples with graphite additive. The data also show that with the Addition of graphite The lubricity shows the tendency over longer periods of time to be maintained at substantially the same levels. this shows yourself by the fact that while later Stages of friction test no significant increase in the coefficient of friction present. moreover showed a visual check of the Samples after the friction tests that pure graphite (columns completely right) showed a tendency to detach to a certain extent while the BN-graphite combinations a considerable one Retained liability. The lubricant mixture thus offers the Advantage of an improved lubricity in connection with a Long-term adhesion under friction.

It should be understood that while the present invention with reference to possibly preferred embodiments, Constructions and procedures have been illustrated and described Embodiments, Constructions and procedures are illustrative only and that the invention is by no means limited to these. Rather, it is being considered undoubtedly drawn to a specialist modifications and variants that will incorporate the principles of the invention. It is therefore considered drawn and it is intended that the invention be limited to all such Variations and variants should extend that the broad Aspects of the invention within its true spirit and scope lock in can.

Claims (18)

Comprising metal forming processes at elevated temperatures the steps that: a metal workpiece to a temperature of at least 250 degrees C is heated; a lubricant formulation on a (a) metal workpiece surface and / or (b) an area a mold design tool is applied; the metal workpiece in the Mold design tool is deformed such that it matches the surface of Molding tool substantially matches; and the metal workpiece from the Mold design tool is removed, wherein the lubricant formulation boron nitride in combination with not less than about 5% graphite. The invention of claim 1, wherein the metal forming process a rapid plastic deformation is. The invention of claim 1, wherein the metal forming process is a superplastic forming. The invention of claim 1, wherein the metal forming process hot working using complementary punch and die forming tools is. The invention of claim 1, wherein the metal forming process is an aluminum forming process. The invention of claim 1, wherein the metal forming process is a magnesium forming process. Comprising metal forming processes at elevated temperatures the steps that: a metal workpiece to a temperature of at least 250 degrees C is heated; a lubricant formulation on a (a) metal workpiece surface and / or (b) an area a mold design tool is applied; the metal workpiece in the Mold design tool is deformed such that it matches the surface of Molding tool substantially matches; and the metal workpiece from the Mold design tool is removed, the lubricant formulation essentially boron nitride in combination with about 10% to about 50% graphite exists. The invention of claim 7, wherein the metal forming process a rapid plastic deformation is. The invention of claim 7, wherein the metal forming process is a superplastic forming. The invention of claim 7, wherein the metal forming process hot working using complementary punch and die forming tools is. The invention of claim 7, wherein the metal forming process is an aluminum forming process. The invention of claim 7, wherein the metal forming process is a magnesium forming process. Elevated temperature metal forming process comprising the steps of: heating a metal workpiece to a temperature of at least 250 degrees C; a lubricant for is applied to a (a) metal workpiece surface and / or (b) a surface of a mold design tool; the metal workpiece in the mold design tool is deformed to substantially coincide with the surface of the mold design tool; and removing the metal workpiece from the forming tool, wherein the lubricant formulation consists essentially of boron nitride in combination with about 5% to about 33% graphite. The invention of claim 13, wherein the metal forming process a rapid plastic deformation is. The invention of claim 13, wherein the metal forming process is a superplastic forming. The invention of claim 13, wherein the metal forming process hot forming using complementary punching and die-shaping tools. The invention of claim 13, wherein the metal forming process is an aluminum forming process. The invention of claim 13, wherein the metal forming process is a magnesium forming process.