DE19604869C2 - Process for applying a layer of non-ferrous metal to a compression molding - Google Patents

Description

The invention relates to a method for applying a firmly adhering layer of non-ferrous metal on an ins special tempered, molded part made of steel.

When coating, a firmly adhering layer is formed shapeless material placed on a workpiece. The custom The easiest coating process is the hot dip coating drive, especially hot-dip galvanizing. Furthermore can a coating by galvanic or electrolytic Deposition from solutions, in the metal spraying process or can be achieved by diffusion.

Non-ferrous metal coatings, especially zinc or Aluminum play a very important role in corrosion protection role.  

Are hot-dip or electrolytic however for high-strength steel tempered in the press tool components less well suited, because here relatively thick, we little ductile coatings or the risk of what hydrogen embrittlement exists. In addition, the material microstructures are adversely affected.

Furthermore, the feasible layer thicknesses are un limited, which among other things causes problems downstream resistance welding processes can result nen.

From CH-PS 297 966 a process for the production metallic coatings on fittings, in which the Fittings in a closed vessel together with a metal powder of impact Expose bodies by moving the vessel.

The disadvantage of this is that the vessel is together must be moved with the fitting. The movement must be intense to ensure coating success Afford. Pressed parts would be with such a loading Layering damaged or worn. That too is apparatus-related expenditure great. Is particularly disadvantageous however, that a metal powder together with impact bodies, namely steel balls is used. Therefore, for recovery and processing of the components a complex separation is required. Furthermore subject to also the impact body wear so that it need to be replaced regularly. Well worn and in the Coating trapped particles of the impact body can also change the quality of the applied coating adversely affect, especially with regard to their Adhesion properties and corrosion resistance.

EP 0 408 818 A1 describes a similar proposal, in which two or more metal powders together with Be layering bodies are moved in a vessel. The Me tall powder should by the impact of the Be Alloy the laminate mechanically and on the loading create a coating from them.

The mechanical coating is from US-A-4 714 622 in the blasting process using a mixture of Known metal powder and steel scrap. Here is a Compatible mixture of a metal powder and Steel scrap produced, the particle size of the Pu which must not be larger than 0.4 mm and the steel scrap should not be less than 0.25 mm.

The disadvantage here is first of all the complex production of the coating mixture in appropriate weight and volume ratios. Furthermore, it is complex Recovery and separation of components in the An after the coating is necessary. Fine iron par particles that arise during the steel process must through an additional magnetic separation during the pro will be deducted. Still, it can be a disadvantage Influence on the quality of the coating is not sufficient be closed.

The proposal of DE-AS 11 44 076 relates to a method for the production of metallic coatings on non-metallic objects by applying metal powder or without impact material in a gaseous medium or in a vacuum, requiring an additive that on the surface of the object to be coated creates a thin film. Organic additives or inorganic substances applied, for example Plastics, synthetic resins or heavy metal sulfides.

This procedure is complex and costly. Here, too, the object to be coated must be for one longer time together with the mixture in a stream mel be rotated. To make a layer of Non-ferrous metal is on a pressed part made of steel this method is not suitable.

The invention is based on the prior art Task based on a method of applying a firm adhering layer of a non-ferrous metal on a Show molded part made of steel, which application is technically cheap and economical and high Quality of the layer guaranteed.

According to the invention, this object is achieved in the features of claim 1.

Advantageous further developments of the reason according to the invention are in the dependent claims 2 and 3 cha characterizes.

The method according to the invention is initially based on a Pretreatment of the structure formed in a press tool hand out. Especially when a compensation in the press tool tion has been made, the mold parts an oxide layer after leaving the tool (Tinder). During the pretreatment, the upper surface of the molded part by blasting cleaned, leaving the oxide layer and other impurities removed and the surface roughened becomes. Here come blasting media of the usual kind like  Slag or glass. After this treatment the surface of the molded part has a defined, roughness required for the subsequent steps.

The load-bearing capacity of the Molded parts can be increased by cold hardening. This is with molded parts that a swell or change exposed to stress, advantageous.

After the pretreatment, the surface of the press mold partially irradiated with a non-ferrous metal shot. Zinc is particularly suitable for this. In this way can provide effective corrosion protection for the molded part due to a complete covering layer made of zinc with good haf tion properties can be achieved. Of course but it can also be shot from another non-ferrous metal, for example aluminum or copper or a purpose speaking alloy.

Shot of different grits is used as the abrasive with a diameter <2 mm. It has been shown that Shot in the diameter range from 0.4 mm to 2 mm in particular which is well suited.

The grist is loaded onto the upper at high speed surface applied. This can be done pneumatically Jet blower using compressed air as well as mechanically Centrifugal jet machines happen. With centrifugal jet The abrasive is machined using the centrifuge accelerated gale force by blast wheels.

When the shot grains hit the surface of the These press parts deform plastically. Here la part of the non-ferrous metal accumulates on the factory surface. It forms an intense one Detention area. Through a suitable process control or  -control it is possible to completely cover layers with good adhesion properties.

The beam intensity, especially the beam speed speed and the abrasive volume flow as well as the Beam duration and beam guidance are dependent controlled by the required layer quality. On this way a high degree of coverage and a uniform Layer thickness reached and there is an equal moderate resistant non-porous coating.

Jet speeds between have been found to be favorable 80 m / s to 180 m / s have been proven, with the volume flow at The shot used depends on the molded part and layer quality can be between 30 kg / min and 200 kg / min.

The ricocheted shot can be further or revered turn. If necessary, it will be reused processed.

The method according to the invention is simple, economical automatable and easy. It leaves a high Throughput too and is for both rewarded and unpaid Molded parts suitable. You can also use other methods necessary process steps, such as pickling, intermediate storage or drying.

Coating systems can be saved because for the Coating used blasting systems of the usual type become. These are often present, for example in Press tool tempered molded parts after leaving one Can have scale layer, the removal by Blasting treatment is carried out. On existing systems can therefore be used.

Claims (3)

1. Method for applying a firmly adhering layer made of a non-ferrous metal on one, especially ver quality, molded part made of steel, in which the Surface of the molded part first by a Blast treatment cleaned and roughened and after this surface treatment with grist from the Non-ferrous metal is irradiated. 2. The method according to claim 1, characterized characterized that grist from grains different diameters less than 2 mm ver is applied. 3. The method according to claim 1 or 2, characterized characterized in that shot blasting both the beam intensity, the beam duration and the Movement of the jet to the molded part or the movement supply of the molded part to the beam logically controlled depending on the specific molded part required layer quality of the non-ferrous metal is taken.