US3923673A - Metal deforming process - Google Patents

Abstract

A process is provided for the deforming of metal such as in deep drawing which comprises applying to the metal prior to the deforming operation certain oil-modified block copolymers.

Description

United States Patent Van Henten et al.

Dec. 2, 1975 METAL DEFORMING PROCESS Inventors: Klaas Van Henten, Delft; Cornelis Couvee, Rotterdam; Dirk De Jager, Delft, all of Netherlands Assignee: Shell Oil Company, Houston, Tex.

Filed: Nov. 9, 1973 Appl. No.: 414,488

Foreign Application Priority Data References Cited UNITED STATES PATENTS Cox 252/59 Armstrong et a1... 252/59 X lsaacson et a1. 252/59 X Luther et a1 117/132 CB Rosenberg et al. .1 1 17/63 Primary Examiner-Delbert E. Gantz Assistant ExaminerAndrew H. Metz ABSTRACT A process is provided for the deforming of metal such as in deep drawing which comprises applying to the metal prior to the deforming operation certain oilmodified block copolymers.

6 Claims, 1 Drawing Figure METAL DEFORMTNG PROCESS BACKGROUND o TIIE INvENTIoN The shaping of metal for a multitude of end uses has involved a great variety of surface-applied materials which normally perform the function of separating from direct contact the metal surface from the shaping mechanism. This can take the form, for example, of a press or a die as in the case of a drawing downward to form wire. While each of the types of deforming operations has different requirements in this respect, they all essentially are based upon the ability to shape the metal to the desired form without causing scoring, gauling or fracture of the metal being so treated.

Another aspect of metal forming operations involves the storage period prior to such operations wherein the metal often is procured for periods up to several months, for example, prior to its use. During this storage period the metal surfaces are subjected to corroding influences including the action of water, oxygen, S H 5 and other acid forming gases or vapors.

For want of a better term, the material applied to the metal surface to relieve the stress of the deforming operations can be referred to as a lubricant even though the material may be in fact a solid or polymeric substance. The lubricants may be applied as or in oils, emulsions, solutions, or powders. In many instances, the lubricant so deposited does not immediately form a continuous film and therefore exposes a portion of the surface of the metal to the corroding influences referred to above. Furthermore, it appears that one of the most critical limitations inherently possessed by most of the previously employed lubricants is their sensitivity to decomposition at the nearest point of contact between the metal surface and the shaping mechanism. For instance, the unit pressures encountered even in shallow drawing of sheet steel are of the order of 1,000 psi, but may exceed 300,000 psi in bar drawing of high tensile'materials. Because of these extreme presssures, contact temperatures may be in the order of 600F or higher during such Common operations as wire drawing. It is evident, therefore, that many materials are subject to instantaneous decomposition at the point of contact and may lose their effectiveness at that time as metal lubricants. Furthermore, during the storage periods preceeding the deforming operations, some polymers may decompose and either expose the metal surface or result in relatively poor operation as lubricants during deforming operations.

Among the great variety of lubricants proposed and utilized, oils have been employed as well as pigmented emulsions, extreme pressure compositions, soap films, sulfide or phosphate coatings, sulfurized oils, chlorinated oils, oxalate coatings solid powders such as graphite, products such as tallow and fats and a great variety of combinations of the same. Certain polymers have been investigated for this purpose including polyolefins and hydrogenated polymers of conjugated dienes. However, each of these has been found to have limitations, particularly wherein extreme requirements are encountered as in deep drawing operations.

An ideal lubricant, particularly in deep drawing oper ations, should be one capable of satisfactory lubricating both in the deformation in mill direction and, simulta-'.

neously, perpendicular to mill direction. If a polymeris deficient in this respect, it may result in rupture at the 7 cating oils are little better in this operation and poly- OBJECTS OF THE INVENTION STATEMENT OF THE INVENTION Now, in accordance with the present invention, a process for the deforming of metals is provided which comprises coating the metal with a lubricant comprising an oil-modified block copolymer havingat least one polymer block A of a monoalkenylarene and at least one polymer block B of a conjugated diene, and thereafter subjecting the coated metal to mechanical deformation.

The present invention is based upon the discovery that these non-hydrogenated block copolymers when modified with a petroleum lubricant provide an essentially ideal deforming lubricant and moreover provide a stable protective surface for the metal parts prior to and during the deforming operations.

The block copolymers used in this invention have the minimal structure A-B, and the preferred structure of A-B-A, but may utilize more complex structures which are either linear or branched. Typical polymers are the following:

polystyrene-polyisoprene polystyrene-polybutadiene polystyrene-polybutadiene-polystyrene poly( a-methylstyrene )-polyisoprene-poly( a-methylstyrene).

The polymer blocks A are monoalkenylarene species 3 such as polystyrene, poly-(tert-butylstyrene) or poly( amethylstyrene). The polymer blocks B are conjugated diene polymer blocks. While homopolymeric blocks are preferred, copolymeric blocks may be employed as long as blocks A on the one hand and b ocks B on the other predominate in the species referred to above. Block molecular weights may vary over a wide range; thus, for example, the polymer blocks A may have number average molecular weights between about 4,000 and 100,000, preferably between about 10,000 and 50,000. Polymer blocks B may have average molecular weights between about 20,000 and 1,000,000, preferably between about 25,000 and 150,000. The molecular weights referred to herein may be determined, for example, by tritium counting methods or osmotic pressure methods. V

The block copolymers are applied to the metal surfaces as oil dispersions which comprise 5 to 50% of the block copolymer and 50-95% by weight of an oil. When the oil is of petroleum origin or other hydrocarbon source, a selection of the type of oil may be made with the. variables being the proportions of aromatic, naphthenic and paraffinic constituents. It is preferred that such oils contain no .more than about 30% by weight aromatic hydrocarbons. The compositions of this type may be applied to the metal surface by painting or spraying. This may be a single operation or may entail multi-stage operations in which, for example, the

3 metal is first sprayed or painted with the oil and thereafter the block copolymer in the form of powders are blown or sprayed onto the oily surface. When storage periods are contemplated prior to the deforming operations, it is desirable to apply the block copolymers in a form which results in a surface coating which is essentially dry to the touch and is essentially non-tacky.

The oil-modified block copolymers may be applied to the metal surface as powders, melts, solutions in relatively volatile solvents, as oil dispersions or in emulsion form or colloidal dispersions. The block copolymers may be used without further modification or may be compounded for specific purposes. The following lists illustrate the materials which may be utilized together with the block copolymers for the purposes of this invention. Solid Inorganic Lubricants graphite molybdenum sulfide zinc phosphate borax plumbago wax Polymeric Lubricants polysulfide rubbers (Thiokols) polyvinyl chloride polychloroprenes nylon polyethylene polypropylene polytetrafluroethylene Extreme Pressure Agents tritolyl phosphate tributyl phosphate tricresyl phosphate trioctyl phosphate sulfurized fats soaps Oils vegetable oils and their acids aliphatic diesters (e.g., di-Z-ethylhexyl sebacate) polyalkylene oxides polyoxyalkylene glycols Resins A. Tackifying Resins Copolymers of piperylene and 2-methyl-2-butene (Wingtack 95 Goodyear) Rosin Hydrogenated rosin Raw esters Polyterpenes B. Reinforcing Resins Coumarone-indene resins Alpha-methylstyrene/vinyl toluene copolymers Styrene/indene/isoprene copolymers Primers Chlorinated and carboxylated atactic polypropylene Carboxylated atactic polypropylene The coating may be effected under more economic means by compounding the block copolymers with relatively compatible polymers such as polypropylene and/or resins typified by those listed hereinabove. Adhesion of the block copolymers .to the metal surface is enhanced by utilizing certain primers which may be applied to the metal prior to application of the block copolymer or may form a part of the block copolymer. coating composition. Adhesion to the metal is also promoted by the placement of polar substituents on the block copolymer or on a fraction thereof, such as-by chlorosulfination, chlorination, hydroxylation or carboxylation. Such derivatized block copolymers are included within the concept of the block copolymers forming the essential lubricant of this invention (as long as their polar substituents comprise no more than about 2% by weight of the block copolymer) or may constitute an additive which may be mixed with the otherwise unmodified block copolymers.

One of the most effective types of compositions showing optimum corrosion resistance properties as well as having promising lubricant properties during deforming operations comprises compositions of the block copolymer, polyvinylchloride and trihydrocarbyl phosphates. Polyvinylchlorides have only borderline compatibility with the block copolymers but form surprisingly satisfactory compositions with the latter when the phosphate is present as what may be referred to as a compatibilizing plasticizer. Preferably a composition of this type comprises parts by weight of the block copolymer, 10-100 parts by weight of the polyvinylchloride and 5-150 parts by weight of the phosphate.

The lubricants of this invention provide nearly ideal lubrication, particularly in deep drawing operations as indicated by the point on the graph forming the figure and labeled thermoplastic rubber. The reason for this is obscure. It has been found, however, tht with many other types of polymers excessive lubrication may lead to wrinkling or buckling, while poor lubrication can cause tearing of the metal. The deforming problems become most serious when forming unsymmetrical parts which involve simultaneously drawing and stretching. Friction between the tools and the work piece predominates in reorganized areas and scoring may occur when less satisfactory lubricants are employed. Viscosity and lubricity may be factors qualifying the end result. In other systems, it has been indicated that lubricity improves with an increase in viscosity. However, it became apparent that for a given set of conditions there is an optimum viscosity above which only a negligible benefit is obtained. This in turn indicates that the advantages of the present invention are not based alone upon the inherent viscosity of these block copolymers although this may aid the result to a certain extent.

Other compositions found to be especially useful in this process comprise the block copolymers modified with petroleum waxes and sulfides or phosphates. The latter may chemically react with the metal surface while the wax performs a function of lubrication which, however, is insufficient in the absence of the block copolymer. Preferably compositions of this type comprise 100 parts by weight of the block copolymer, 10-100 parts by weight of petroleum wax and l-SO parts by weight of sulfides or phosphates such as those listed in the disclosure.

The metals contemplated for treatment in the process of this invention include particularly iron, steel, brass, aluminum, copper, titanium and the like. The deforming operations considered here include cold or hot working, shallow or deep drawing of sheets or bars or other shapes as well as extrusion and stamping.

What is claimed is:

. 1. process for deforming metal which comprises applying to the surface of said metal a composition comprising 550% by weight of a non-hydrogenated block copolymer having at least one homo polymer block of a monoalkenylarene selected from the group consisting of styrene, alpha-methylstyrene and tertbutyl styrene, said block having an average molecular weight between about 4000 and 100,000 and at least one homo polymer block of a conjugated diene selected from the group consisting of butadiene and isoprene, said block having an average molecular weight between about 20,000 and 1,000,000, and 50-95% by weight of a hydrocarbon lubricant, said lubricant containing no more than about by weight of aromatic hydrocarbons and subjecting the metal so treated to deforming operations.

2. A process according to claim 1 wherein the composition is applied to the metal surface as a hot melt.

3. A process according to claim 1 wherein the block copolymer has the structure polystyrene-polybutadiene-polystyrene.

4. A process according to claim 1 wherein the composition comprises 1030% of block copolymer and of a petroleum wax.

5. A process according to claim 1 wherein the composition is applied to the metal in the form of a powder.

6. A process according to claim 1 wherein the lubricant comprises a petroleum hydrocarbon lubricating oil.

Claims (6)

1. A PROCESS FOR DEFORMING METAL WHICH COMPRISES APPLYING TO THE SURFACE OF SAID METAL A COMPOSITION COMPRISING 5-50% BY WEIGHT OF A NON-HYDROGENATED BLOCK COPOLYMER HAVING AT LEAST ONE HOMO POLYMER BLOCK OF A MONOALKENYLARENE SELECTED FROM THE GROUP CONSISTING OF STYRENE, ALPHA-METHYLSTYRENE AND TERT-BUTYL STYRENE, SAID BLOCK HAVING AN AVERAGE MOLECULAR WEIGHT BETWEEN ABOUT 4000 AND 100,000 AND AT LEAST ONE HOMO POLYMER BLOCK OF A CONJUGATED DIENE SELECTED FROM THE GROUP CONSISTING OF BUTADIENE AND ISOPPERENE, SAID BLOCCK HAVING AN AVERAGE MOLECULAR WEIGHT BETWEEN ABOUT 20,000 AND 1,000,000, AND 50-95% BY WEIGHT OF A HYDROCARBON LUBRICANT, SAID LUBRICANT CONTAINING NO MORE THAN ABOUT 30% BY WEIGHT OF AROMATIC HYDROCARBONS AND SUBJECTING THE METAL SO TREATED TO DEFORMING OPERATIONS.

2. A process according to claim 1 wherein the composition is applied to the metal surface as a hot melt.

3. A process according to claim 1 wherein the block copolymer has the structure polystyrene-polybutadiene-polystyrene.

4. A process according to claim 1 wherein the composition comprises 10-30% of block copolymer and 70-90% of a petroleum wax.

5. A process according to claim 1 wherein the composition is applied to the metal in the form of a powder.

6. A process according to claim 1 wherein the lubricant comprises a petroleum hydrocarbon lubricating oil.