CS220162B1 - Pickling bath for treatment of blasted surface of alloyed steel castings and forgings - Google Patents

Abstract

The invention falls into the field of chemical treatment of metal surfaces and solves the problem of eliminating toxicity and stabilizing the effect of pickling baths for treating the blasted surface of castings and forgings made of alloy steels. The essence of the invention is that the pickling bath in 100 l of aqueous solution contains 5 to 20 kg of potassium hydrosulfate, 3.5 to 10 l of sulfuric acid with a density of 1840 kgm-3 and 5 to 10 l of phosphoric acid with a density of 1630: kgm-3.

Description

(54) Pickling bath for treatment of blasted surface of alloy steel castings and forgings

The present invention is in the field of chemical treatment of metal surfaces and solves the elimination of toxicity and stabilization of the effect of pickling baths for treatment of the blasted surface of castings and forgings of alloy steel. It is an object of the invention that the pickling bath in 100 l of aqueous solution contains 5 to 20 kg of potassium hydrogen sulphate, 3.5 to 10 l of sulfuric acid of 1840 kgm- ³ and 5 to 10 l of phosphoric acid of 1630: kgm- ³ .

BACKGROUND OF THE INVENTION The present invention relates to a pickling bath for the treatment of shot blasted surfaces of alloyed steel castings and forgings.

In the production of cast or forged machine parts from alloyed materials, for example in the production of castings, industrial fittings components adhere to the surface of ceramic residues and create undesirable metal inclusions. For these products, the surface must be metallic clean for further processing and possible subsequent surface treatment. Therefore, the individual parts are first sprayed with cast iron grit or shot and then pickled in a bath to remove unwanted inclusions or ceramic residues.

Although existing baths are sufficiently effective, they are either unsuitable in terms of undesirable leakage of toxic gases or in terms of other operational disadvantages, in particular with regard to the possibility of liquidating baths and rinsing waters. For example, baths containing nitric or hydrochloric acid are unsatisfactory due to the development of toxic gases and due to the demanding disposal process. Another alkaline reduction bath with sodium hydride used is very sensitive to moisture in the working state and, in the unfavorable case, an explosive bath may be splashed. Also the disposal of rinsing water is very difficult due to the high salinity and presence of other undesirable substances.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pickling bath which retains the desired effects but at least substantially reduces unwanted side effects.

This object is solved by the object of the invention, which is a pickling bath for treatment of the blasted surface of castings and forgings of alloy steel, which consists in that it contains up to 20 kg of potassium hydrogen sulphate in 100 l of aqueous solution.

3.5 to 10 L sulfuric acid density

1840 kgm ^-3 and up to 10 l of phosphoric acid density

1630 kgm ^-3 .

The pickling bath according to the invention, with the same working result, has a higher effect in that it is not sensitive to the introduction of water and, on the other hand, does not evolve from toxic fumes which could adversely affect the working environment. the associated rinsing water is easily disposed of.

Examples of the composition of the pickling bath according to the invention and the procedure for treatment of alloy steel castings and forgings.

Example 1

The blasted parts are pickled for 10 to 20 minutes at a temperature of 40 to 50 ° C in a bath containing 100 kg of potassium hydrogen sulphate per 100 l of aqueous solution.

101 sulfuric acid with a density of 1840 kgm ^-3 a

1 phosphoric acid with a density of 1630 kgm ^-3

Example. 2

The blasted parts are pickled for 20 minutes at a temperature. 60 to 70 ° C in a bath containing 100 kg of aqueous solution containing 1 kg of potassium hydrogen sulphate ·

1 density sulfuric acid, ·

1840 kgm ^-3 and phosphoric acid with a density of 1630 kgm ^-3

Example 3

The blasted parts are pickled for 10 to 20 minutes at 50 to 60 ° C in a bath containing 100 kg of potassium hydrogen sulphate per 100 l of aqueous solution.

3,5 l phosphoric acid with a density of 1840 kgm ^-3 a

1 phosphoric acid with a density of 1630 kgm ^-3

Example 4

Parts with large, continuous ceramic surface fields are sputtered for 20 minutes at 70 ° C in a bath containing 100 kg of potassium hydrogen sulphate per 100 l of aqueous solution.

1 sulfuric acid, density 1840 kgm ^-3 a

1 phosphoric acid

Then, the parts are rinsed, a second blasting is performed and repeatedly pickled for 20 minutes in the same bath at 50 ° to 6 ° C.

In all cases, after the pickling, a cold neutralization step is carried out successively for at least 3 minutes, for example in a sodium carbonate bath, followed by a further cold water rinse for at least 5 minutes and finally a hot water rinse for at least 5 minutes.

The pickling bath is supplemented with potassium hydrogen sulphate and sulfuric acid during operation to maintain the same degree of efficiency. At an iron content of 70 to 90 g / l, depending on the degree of contamination of the surface of the parts, the bath must be replaced. The bath and rinsing water used are neutralized by precipitation of all components with lime milk to achieve a pH of 7.5 to 8.0. After sedimentation of the resulting precipitates, the water can be discharged into waste.

The pickling bath according to the invention can be used wherever a metal-clean surface is to be obtained for castings and forgings of alloyed steels.

Claims (3)

SUBJECT Pickling bath for treatment of blasted surface of castings and forgings of alloy steel, characterized in that in 100 l of aqueous solution it contains 5 to 20 kg of potassium hydrogen sulphate of the invention 3,5 to 10 l of sulfuric acid, density 1840 kgm ^{3 3} a 5 to 10 liters of phosphoric acid with a density of 1630 kgm ^-3 .