DD299074A5 - LUBRICANTS ON AN ORGANIC BASE FOR PRESSING AND PULLING - Google Patents

Abstract

The invention relates to an inorganic-based lubricant for pressing and drawing materials such as aluminum, titanium, tantalum, niobium, zirconium and their alloys at temperatures up to 923 K. The lubricant consists of species-specific oxides, which in a multilayer structure consisting of highly crystalline barrier layer, semi-crystalline oxide layer and coarse-pored semi-crystalline oxide matrix layer. {Lubricants; Press; Pull; Aluminum; Titanium; tantalum; Niobium; zircon; native oxides; Multilayer structure}

Description

Field of application of the invention

The invention relates to an inorganic-based lubricant for pressing and drawing materials such as Al, Ti, Ta, Nb, Zr and their alloys at temperatures up to 923K and is applicable in the metalworking industry.

Characteristic of the known state of the art

Many metals, but especially titanium, niobium and tantalum, are not used in forming processes, e.g. the cold extrusion or wire drawing very siark to welds with the tool or they can be reshaped insufficiently or with great technical effort.

There are therefore a number of special interface lubricant systems have been developed that allow the cold forming of these metals with economically justifiable effort. These include in particular combinations of lubricant carrier layers such as oxide layers (DD 231923) phosphate coatings or sodium fluoride-based coatings and lubricants such as colloidal graphite in water, paints, molybdenum sulfide, graphitized vegetable oils, fluoridated hydrocarbons and mica, talc, low-melting salts, soaps or solid lubricants based on d 3r of fluorotelomers.

These lubricants are either poorly adherent or less stable, so that they are decomposed in the forming process and partially toxic substances. Therefore, the use of metals as a lubricant is widely used, in particular copper being used in addition to silver, magnesium, zinc, cadmium, tin or aluminum.

However, these substances are not always desirable on the semifinished product to be formed. According to DE-OS 3210304 e.g. Titanium semifinished product is provided prior to extrusion or extrusion with a copper layer, which must be removed electrolytically again after the forming process.

Apart from the great technical effort, such a procedure has the disadvantage that no precision parts without subsequent surface processing can be produced in this way. Increasingly, the relatively expensive titanium and vanadium metals are being used in areas where the surface quality of the workpiece substantially determines its utility in terms of composition, topography and processing. So z. As the application of most of the lubricants mentioned in the manufacture of implants made of titanium or tantalum due to the deterioration of biocompatibility excluded from the outset or it must be made cumbersome cleaning and control measures.

On workpieces made of titanium, niobium, zirconium or tantalum in the reactor or vacuum technology, similar demands are placed on the purity of the surface as on implants, which do not allow the use of most lubricant additives.

Object of the invention

The aim of the invention is to improve the semi-finished surface quality in the forming processes, to reduce tool wear and to increase the forming speeds and thus to increase the productivity.

Explanation of the essence of the invention

The invention has for its object to develop a stable during forming lubricant for pressing and pulling, which prevents welding of the tool with the metal even under extreme forming conditions and has good properties as a lubricant or lubricant carrier has. According to the invention, the object is achieved in that the lubricant is a multi-layer structure of species-specific oxides with siner metal side 70-300nm strong crystalline barrier layer as Oxydationschute and an overlying fine-pored semi-crystalline oxide layer of 0.5-1.5 pm thickness, which acts as a release agent and the in thickness, degree of crystallinity and porosity from the outer oxide matrix layer; as a lubricant layer of 4 to 20μηη strength significantly different, has.

This outer strongly porous, partially crystalline oxide matrix layer contains at least 40% X-ray amorphous oxides and the incorporated phosphates in the form of polyphosphates and boron compounds, in particular borates and / or boron nitrides in a concentration of 1 to 20%. The X-ray amorphous and crystalline portions are homogeneously distributed in the oxide matrix layer as are the phosphates and borates. The boron nitrides, however, are enriched in the outer zone of the oxide matrix layer.

In addition, the outer layers of conventional lubricants such. As oils, waxes, fluorinated hydrocarbons, but also molybdenum sulfide, graphite> 5% record. It was not to be expected that these additionally applied liquid and / or solid conventional lubricants' are so firmly bound that they are still detectable and homogeneously distributed even after repeated forming on the workpieces.

An advantage of the invention is therefore also that this significant three-layer structure passes through the high activity of the outer sliding layer as well as the adsorption and chemisorption of conventional lubricants in a hr-effective lubricant composite, which may be constructed so that builds up a closed lubricant film of conventional lubricants ,

Another advantage of the invention is that this lubricating layer composite can be applied to any surface and that even without additional conventional lubricants a greater separation and sliding effect is achieved over a naturally formed or galvanically reinforced oxide layer on the material.

Surprisingly, a lubricant effect is achieved by the multi-layer structure of the lubricant, which makes it possible to significantly increase the surface quality of the materials to be formed, even under extreme forming conditions.

Ausführungsbeisplele

The invention is explained in more detail below with reference to two examples:

example 1

On an aluminum bolt of 320 mm length and 80 mm diameter is in an electrolyte, the 0.4 molar of Na (H ₂ PO ₄ ), 0.1 molar of Na ₂ (HPO ₄ ), 0.1 molar of Na ₃ PO ₄ , 0.2 molar each of (NH ₄ I ₂ HPO ₄ and Na ₂ B ₄ O ₇ and 0.1 molar of Ca (H ₂ PO ₄ J ₂ and 0.01% Marrelan and 5g / l boron nitride contains , at an electrolyte temperature of 333 K by means of a pulse voltage with voltage peaks of 210V, at an impulse frequency of 100Hz, the smear layer compound, consisting of a 210nm strong oxidation protection layer, 0.9pm strong low pore separation layer and 19pm strong sliding layer 35% X-ray amorphous aluminas In addition to about 25% polyphosphates, 5% borates and ~ 1% boron nitride, 20% Y-Al ₂ O ₃ and - 10% Ci-Al ₂ O _{3 are still} detected 26% This lubricating layer composite exhibits excellent sliding and separating properties when pressed against the 010mm round profile at 623K.

Example 2

On a Ti-bolt of 320 mm in length and 80 mm diameter, the lubricating layer composite is generated in accordance with the film formation parameters of Example 1, which is characterized by a 185nm strong Oxydationsschutzschicht, 0,6μπι strong separating layer and a 14 μιη sliding layer. In addition to about 20% X-ray amorphous titanium oxides, the layer contains about 15% polyphosphates, 4% borates and ~ 1% boron nitride. The pore volume of the sliding layer is about 18%. To form an additional lubricant layer, the three-layer stud is treated with beeswax at 573K. The bolt is then heated to 873K and pressed. The excellent sliding and separating properties of the o.g. Lubricant layers gave a very good strand surface quality and low roll wear.

Claims (3)

1. inorganic-based lubricant for pressing and drawing materials such as Al, Ti, Ta, Nb, Zr and their alloys at temperatures up to 923 K, characterized in that it is a multi-layer structure of native oxides with a metal-side 70-300 nm strong crystalline A barrier layer and an overlying fine-pored semi-crystalline oxide layer of 0.5-1.5Mm thickness, wherein the Oxidmatrixschichi at least 40% X-ray amorphous oxides and phosphates in the form of polyphosphates having a concentration of 1% to 20% and borates and / or boron nitrides in a concentration from 1 to 20%. 2. A lubricant according to claim 1, characterized in that the oxide matrix layer additionally contains liquid or solid lubricants preferably oils, waxes and / or molybdenum sulfide, graphite of 5-20%. 3. A lubricant according to claim 2, characterized in that a closed lubricant layer is present on the oxide matrix layer.