US3869894A - Method of treating iron and steel workpieces prior to cold working - Google Patents

Abstract

Disclosed is a method for treating iron and steel workpieces prior to cold working. The workpieces are pretreated to a temperature of 50*-150*C. and contacted with an aqueous suspension containing solid lubricants of laminar lattice structure. The parts are simultaneously subjected to relative movement so as to cause intercontact between the parts for a period of time sufficient to permit evaporation of a predominant part of the water in the suspension. The quantity of suspension employed is sufficient to yield 5-50 g. active content/m2 workpiece surface area.

Description

United States Patent 1191 Meyer et a1.

1451 Mar. 11, 1975 METHOD OF TREATING IRON AND STEEL WORKPIECES PRIOR TO COLD WORKING [75] Inventors: Norbert Meyer, Bruchkobel; Han

Yong Oei, Frankfurt am Main; Werner Rausch, Oberursel; Horst Schneider, Frankfurt am Main, all of Germany [73] Assignee: Oxy Metal Finishing Corporation,

Warren, Mich.

22 Filed: Nov. 5, 1973 21 Appl. No.: 413,102

[30] I Foreign Application Priority Data Nov. 7, 1972 Germany ..2254378 [52] US. Cl 72/42, 72/46, 117/109, 148/6.15 R

[51] Int. Cl. B21j 3/00, B05c 3/04, C23f 7/10 [58] Field of Search 72/39, 41, 42, 46', 117/D1G. 8, 109; 118/416, 418; 148/6.15 R

[56] References Cited UNITED STATES PATENTS 5/1949 Bramberry 148/6.15 R 3/1958 Herman 117/109 2,894,484 7/1959 Kearney 117/109 2,939,809 6/1960 Jensen ct al. 148/6.15 R

3,013,892 12/1961 Songas 117/109 3,494,327 2/1970 Pearson 118/418 3,507,686 4/1970 Hagenbach 117/109 3,775,323 11/1973 Dubourg 1423/6115 R FOREIGN PATENTS OR APPLICATIONS 1,004,836 9/1965 Great Britain 72/46 Primary Examiner-C. W. Lanham Assistant Examiner-E. M. Combs Attorney, Agent, or Firm-Arthur E Kluegel; Richard P. Mueller; B. F. Claeboe [57] ABSTRACT 5 Claims, No Drawings METHOD OF TREATING IRON AND STEEL WORKPIECES PRIOR TO COLD WORKING BACKGROUND OF THE INVENTION The present invention relates to a method of pretreatment of simply shaped standard parts for chip-free cold working, made of iron and steel, in which aqueous suspensions are used which contain phosphoric acid suspended substances with laminar lattice structure, such as molybdenum disulfide, graphite, as well as surfactants and, where appropriate, other additives. These agents are applied to standard parts under certain conditions of use and certain control specifications.

It is a known practice to use a lubricants for the chipfree cold working of parts oil-free aqueous dispersions of solid lubricants with laminar lattice structure, for example MoS W8 graphite, with the addition of inorganic thickening agents, and, when appropriate, other additives of phosphoric acid, metal phosphates, depolarizers, for example nitrate, nitrite, chlorate, (German Pat. No. 1,103,497). Application is made, for example, by painting on, spraying on or dipping, followed by drying of the film. The indicated procedure is too cumbersome and time-consuming for use with mass-produced small parts.

Aqueous dispersions which contain phosphoric acid, molybdenum disulfide, organic thickeners and, for example nitric acid in addition, are mentioned in British Pat. No. 767,572. The application of the agent to the surface of the workpiece to be shaped takes place by means of brushes, while the additional use of heat will lead to acceleration of the reaction and drying of the coating. The use of this method is also cumbersome and timeconsuming.

A more recent procedure for pretreating small iron parts for chip-free cold working is described in the publication mrv. metallpraxis oberflachentechnik 5, A33-A35 (1972) The workpieces are treated in rotating drums, the contact with solutions being made in that the rotating drums are dipped in the various baths. In detail, the procedure comprises the following steps: cleansing; rinsing with water; phosphatizing, for example with a zinc phosphate solution; rinsing with water at about 80C.; treatment in a stable aqueous suspension at 80-85C., containing molybdenum disulfide, binder and film-forming agent; and rotating the drum in air to dry the parts, with supplementary use of hot air, when required. The procedure here described yields outstanding forming results, but has the disadvantage that it is cumbersome and time-consuming, due to the multiplicity of the various steps.

The method according to the invention, compared with the prior art, offers the advantage that, in a very simple application involving only one stage, small massproduced parts made of iron and steel can simultaneously be phosphatized and given a lubricating coating, while control of the thickness of film, within close tolerances, and its adaptation to the needs of the particular manner of cold working, are possible. Further, it is advantageous that no waste water is produced by the process. Thus, it is a process which does not contribute to pollution by creating waste rinse water.

SUMMARY OF THE INVENTION The method, according to the invention, for the pretreatment of simply shaped iron and steel small massproduced parts of chip-free cold working uses suspensions, in themselves known, which contain phosphoric acid, suspended substances with laminar lattice structure, surfactants and, when required, thickeners, as well as difficultly soluble phosphate-forming cations. It is characterized in that the scalefree workpieces, at a preheated temperature between 50 and 150C., preferably to C, carry out a relative motion with reference to one another in a moving, for example rotating or vibrating, container and thus are brought into contact with so much aqueous suspension that 5-50 g. of active content of the suspension is applied per square meter of workpiece surface. The term active content here means the non-vaporizable portion of the suspension. Motion in the container is continued until the predominant portion of the water has evaporated.

In other words, the improvement comprises preheating the workpieces or parts to a temperature between 50 and C. A relative motion of the workpiece is then effected so as to cause intercontact of the pieces while simultaneously contacting the parts with the above-mentioned suspension, the active content of the suspension being in the range 5-50 g/m of workpiece surface area. The relative motion is continued until a predominant part of the water in the suspension has evaporated.

DETAILED DESCRIPTION OF THE INVENTION The aqueoussuspension which, within the scope of the invention, are used preferably contain so much phosphoric acid that the relation by weight of H PO H O (0.01-0.25) l. The group of laminar structure pigments includes (among others) molybdenum disulfide, tungsten sulfide, boron nitride and graphite. The portion by weight of the laminar structure pigment, preferably, is between 30% and 99% active content. The surfactants used must be stable to acid and are used to wet the metal and/or pigment surface. They may be selected from the group of nonionic, anionic, cationic and even amphoteric surface-active substances. Cationic substances, for example oleic acidimidazoline derivatives, have been found to be very advantageous.

When thickeners are also used, they can be chosen from the group of known inorganic and organic thickening agents. Typical examples are bentonite, finely divided silica, cellulose derivatives, polysaccharides, polyacrylamides and the like. Zinc, calcium, manganese, iron, magnesium and others enter the picture as cations which form difficultly soluble phosphates. In order better to fix the laminar structure pigment of the metal surface, it is possible to use film-forming products, for example acidstable synthetic resin dispersions and water-soluble high molecular organic compounds. Too vigorous evolution of foam during the processs of motion can be counteracted by the use of suitable antifoam agents, for example from the group of silicone oils. The suspensions may, in addition, contain means of enhancing the attack of aqueous phosphoric acid on the steel surface. These include particularly oxidizing agents, such as nitrates, nitrites, hydrogen peroxide and the like. Small amounts of the more noble metals, such as copper, nickel and cobalt have similar effects. It is advantageous to stay within the framework of the following weight percent concentrations for the suspension to be used in connection with the invention:

5. 50% MOS: preferably 20-40% 0.5' 14% H PO preferably 4-8% 070%" 2% thickener preferably 0.14% 0.05 1% surfactant preferably 0.l0.6% Remainder water The workpiece used in connection with the invention include for example wire sections, sheet metal disks, blocks, sections of rods, cylindrical and rectangular metal parts.

It is important that the surface of the workpieces be free of scale and other hard non-metallic impurities. On the hand, thin films of rust, grease or oil do no harm. Phosphatizing of the parts before making use of the method according to the invention is not necessary, but, one the other hand, also does no harm. The envi- -ronment-friendly processes which are suitable for cleaning the workpiece are, particularly, radiation, ignition under protective gas and scouring in drums or vibrating tanks. However, it is also possible to make use of known pickling processes. The preheated temperature of the parts, as required within the scope of the in-- vention, namely 50-l50C., preferably 70100C., can be attained, for example, by heating in an oven, by washing in hot water, as well as by the action of radiation or hot air.

In order to produce the necessary relative motion of the parts, according to the invention, they are placed, for example, in rotating drums, in vibrating troughs or drains. The relative motion can be intensified by incorporating baffles. It is the purpose of these measures that the workpiece will rub together superficially, slide over one another and strike together in the course of the treatment.

The extent of the active content primarily relates to the surface of the workpieces. But, this may also relate to the weight of the workpieces, if there is any more or less reliable relation between surface and weight. The lower range is used for less severe shaping, and the upper range for more severe shaping. It was surprising to find that, with the method according to the invention, the thickness of the lubricating film is relatively uniform even on all surfaces of non-uniformly shaped workpieces.

Treatment in the moving tank is carried out in such a way that, at the end, most of the water has evaporated. The energy required to evaporate the solvent is often furnished adequately by the elevated temperature of the parts. Removal of the solvent vapor can be facilitated by blowing air onto or into the contents of the tank. However, it is also possible, by supplementary use of heat as the parts are being treated, to support the drying process. For this purpose, warm air, thermal radiation, as well as feeding heat onto the walls of the tanks, may be used.

Under certain conditions, it has been found to be desirable to add a neutralizing agent to the contents of the tank, some time after addition of the aqueous suspension. In this way, excess unreacted acids are converted into neutral compounds. These neutralizing agents may, for example, be: zinc oxide powder, calcium oxide powder, calcium carbonate powder, magnesium oxide powder, but also neutralizing compounds from the alkali group, for example sodium carbonate, trisodium phosphate, borax.

Within the scope of the invention, it may be advantageous to feed into the moving tank compressible bodies, in addition to the workpieces. These, for example, may serve to prevent surface damage due too severe impact, when heavy objects are being treated. in the case of compressible bodies, the abrasion of which has a lubricating effect, an additional advantage is the'incorporation of the fines in the lubricating layer. Compressible bodies with lubricating properties include. for example, polyethylene, polypropylene, polyamide and polymeric fluorinated hydrocarbons. The size the number of such bodies per tank filling depend on the nature of the tank motion and the number and size of the workpieces. They may be present as relatively large particles, but the use of fine-grained material is also possible. Under some circumstances, this may be incorporated in the lubricant layer without further comminution.

Table I shows some typical recipes for suitable aqueous suspensions. The procedue, according to the invention, will now be explained, in the light of some Examples:

EXAMPLE 1 100 kg of scaly steel wire sections, with a diameter of 15 mm and a length of l5 mm also, were first pickled in 15% hydrochloric acid at room temperature for 25 minutes, and thus freed of scale. They were then rinsed in water and given a second rinse in water at C. In this way, the pieces gained the necessary preheat temperature.vThey were then transferred into a cylindrical drum with axis of rotation 45-from vertical, and g Agent No. l/m of workpiece surface (Table l) was poured over them. This corresponds to about 39 g active content/m workpiece surface. The parts were tumbled in a drum for 15 minutes, while the drum turned at 30 rpm. Warm air was then blowing in and tumbling was continued for another 5 minutes after which the surface of the workpiece was free of moisture. The pieces showed a uniform coating of molybdenum sulfide and iron phosphate, which adhered firmly to the metallic base. These pieces were shaped into hollow bodies by the cold flow molding process. The operation proceeded without difficulties, that is without the formation of striations on workpiece or tool.

EXAMPLE 2 100 kg of sheet steel discs, with rust and scale-free surfaces, but covered with a thin grease film, 80 mm in diameter and 5 mm thick, were preheated by immersion in water at approximately 100C. They were then transferred to a vibrating trough and, after the addition of 40 g of Agent No. 7 (Table I) were subjected to vibration. The amount of suspension used corresponded to about 22 g active content per m of workpiece surface. The vibration continued for 15 minutes, while warm air was blown over the surface of the parts during the entire time. Here too, a firmly adhering phosphate lubricating film was formed by the treatment, making possible entirely acceptable cold working when the parts were molded into bowls.

Table l PERCENT BY WEIGHT Agent No. 1 3 4 5 6 7 8 MOS, 30 25 25 25 10 WS, 30 Graphite 50 30 3 4 8 5 l0 8 6 8 5 2 Surfactant 0.5 0.5 l 0.5 2 0.5 0.5 0.5 Thickening Agent 0.6 0.6 0.3 1 0.3 0.6 0.3 l AntifoamingPAgent 0.06 0.1 0.05 0. l 0.2 0.06 0. l 0.05 Zinc Orthohosphate 1.5 Manganese Ortho-Phos- 2 3 Py h h l5 inc rop osp ate Calcium Phosphate 3 Water Remainder What is claimed is:

1. In a method for the treatment of shaped iron and steel workpieces prior to cold working, making use of aqueous suspensions which contain phosphoric acid, suspended substances with laminar lattice structures and surfactants, the improvement comprising preheating said workpiece to a temperature between 50 and 150C, effecting a motion of said workpieces relative to each other sufficient to cause intercontact while simultaneously contacting said workpieces with said suspension having active content in an amount of between 5 and 50 g/m of workpiece surface area and comprising 550% of a laminar lattice compound, 0.5-14% H PO and 005-1 surfactant, and continuing said motion until a predominant part of the water is said suspension has been evaporated.

2. The method according to claim 1, wherein the evaporation of the water out of the tank is supported by an external heat source.

3. The method according to claim 1, wherein the aqueous suspension is fed into the moving tank at room temperature.

4. The method according to claim 1, wherein compressible bodies, for example made of polyethylene, polypropylene, polyamide, polymeric fluorinated hydrocarbons, rubber are added to the moving tank, in addition to the workpieces.

5. The method according to claim 1, wherein after the aqueous suspension has acted on the iron and steel workpieces for sufficient time, neutralizing compounds are fed into the tank.

Claims (5)

1. In a method for the treatment of shaped iron and steel workpieces prior to cold working, making use of aqueous suspensions which contain phospHoric acid, suspended substances with laminar lattice structures and surfactants, the improvement comprising preheating said workpieces to a temperature between 50* and 150*C, effecting a motion of said workpieces relative to each other sufficient to cause intercontact while simultaneously contacting said workpieces with said suspension having active content in an amount of between 5 and 50 g/m2 of workpiece surface area and comprising 5-50% of a laminar lattice compound, 0.5-14% H3PO4 and 0.05-1 % surfactant, and continuing said motion until a predominant part of the water is said suspension has been evaporated.

1. IN A METHOD FOR THE TREATMENT OF SHAPED IRON AND STEEL WORKPIECES PRIOR TO COLD WORKING, MAKING USE OF AQUEOUS SUSPENSIONS WHICH CONTAIN PHOSPHORIC ACID, SUSPENDED SUBSTANCES WITH LAMINAR LATTICE STRUCTURES AND SURFACTANTS, THE IMPROVEMENT COMPRISING PREHEATING SAID WORKPIECE TO A TEMPERATURE BETWEEN 50* AND 150*C, EFFECTING A MOTION OF SAID WORKPIECES RELATIVE TO EACH OTHER SUFFICIENT TO CAUSE INTERCONTACT WHILE SIMULTANEOUSLY CONTACTING SAID WORKPIECES WITH SAID SUSPENSION HAVING ACTIVE CONTENT IN AN AMOUNT OF BETWEEN 5 AND 50 G/M2 OF WORKPIECE SURFACE AREA AND COMPRISING 5-50% OF A LAMINAR LATTICE COMPOUND, 0.5-14% H3PO4 AND 0.05-1% SURFACTANT, AND CONTINUING SAID MOTION UNTIL A PREDOMINANT PART OF THE WATER IS SAID SUSPENSION HAS BEEN EVAPORATED.

2. The method according to claim 1, wherein the evaporation of the water out of the tank is supported by an external heat source.

3. The method according to claim 1, wherein the aqueous suspension is fed into the moving tank at room temperature.

4. The method according to claim 1, wherein compressible bodies, for example made of polyethylene, polypropylene, polyamide, polymeric fluorinated hydrocarbons, rubber are added to the moving tank, in addition to the workpieces.