Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
  • B24C3/00—Abrasive blasting machines or devices; Plants
  • B24C3/32—Abrasive blasting machines or devices; Plants designed for abrasive blasting of particular work, e.g. the internal surfaces of cylinder blocks
  • B24C3/325—Abrasive blasting machines or devices; Plants designed for abrasive blasting of particular work, e.g. the internal surfaces of cylinder blocks for internal surfaces, e.g. of tubes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/02—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working in inert or controlled atmosphere or vacuum
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon

Definitions

• the invention relates to a method for producing seamless drawn semi-hard / hard plumbing pipes made of copper, in which the inner surfaces of the pipes are roughened.
• EP 0 306 810 A2 discloses a method for producing pitting-resistant, hard-drawn tubes made of copper or copper alloys, in which the tubes are first degreased and then the inner surfaces of the tubes are additionally treated with an abrasive. Hereby a roughening of the inner surfaces is achieved, by which the formation of harmful films, e.g. avoid carbon-containing films on the inner surfaces of hard-drawn copper pipes.
• pitting corrosion processes involve copper ion migration, but they follow other laws.
• a high corrosion resistance of copper materials, in particular one against pitting corrosion type 1 does not at the same time result in a lower copper ion release to water.
• the invention has for its object to improve this method in such a way that a reduced copper ion release to drinking water with a normal pH in the range of 6.5 to 9.0 can be guaranteed.
• semi-hard or hard copper installation pipes can now be made available, in which the copper ion release to the drinking water can be kept decisively below the required limit values even over a long period of time.
• Such installation pipes are also resistant to pitting corrosion and can be installed with the known connection and bending techniques.
• the process also allows economical production in bar form with the commonly available manufacturing facilities for seamless copper tubes.
• the method according to the invention can advantageously be used in the manufacture of fittings with reduced copper ion release.
• a first process step there is a so-called preference, in which hot-formed front tubes are cold-formed from cast rods by pulling to an intermediate dimension.
• the inner surfaces of these intermediate tubes are then roughened. This is not only intended to promote the oxidic reaction with the inner surfaces, but also to prevent the oxide layer from no longer uniformly covering during the later hardening process in which the inner surfaces are stretched.
• the roughness depth Ra can range between 0.3 ⁇ m and 1.0 ⁇ m.
• the final dimension of the installation pipes is generated by a hardness train to semi-hard / hard.
• a thermal treatment is carried out again at 175 ° C. to 275 ° C. while introducing an oxygen-containing gas mixture into the interior of the tube in order to achieve an oxide layer in a composition of approximately 12% to 21% oxygen with the residual copper content.
• the production process according to the invention substantially reduces the copper ion release compared to the semi-hard / hard copper installation pipes in the form of bars, which have previously been used for the central drinking water supply, with constant resistance to pitting corrosion.
• the maximum copper ion solubility in installation pipes made in this way surprisingly only reaches a value of 1 mg / l.
• the roughening of the inner surfaces of the intermediate tubes can be carried out according to the features of claim 2 by using blasting agents or by pickling.
• an abrasive e.g. Silicon oxide are used.
• the intermediate tubes are preferably annealed in accordance with the features of claim 3 with a protective gas which has an oxygen content of 1% to 7%.
• the annealing process is preferably carried out at a temperature of about 650 ° C.
• a thin, adherent oxide layer with a thickness of approximately 0.05 ⁇ m to 0.2 ⁇ m can thereby be produced.
• the thermal treatment after the hardening train is advantageously carried out at a temperature of about 250 ° C.
• the hardening tension is carried out in particular with an internal mandrel.
• the degree of deformation here is on average 20%.
• the heating can be carried out convectively, electrically inductively or conductively according to claim 8.
• phosphorus deoxidized copper (SF-Cu) was melted and cast into bars. The bars were then further processed into tubes by means of hot forming and then cold formed to an intermediate dimension.
• the intermediate tubes were then continuously heat-treated at a temperature of 650 ° C. while introducing a gas mixture into the interior of the tube.
• the gas mixture consisted of a protective gas with an oxygen content of 3%.
• a firmly adhering thin copper oxide layer with a layer thickness of 0.15 ⁇ m was formed on the inner surface, the oxygen content of which was determined to be 11.2% by means of X-ray diffractometry.
• the intermediate tubes were hard-drawn to their final dimensions using a standard drawing oil with a degree of deformation of 20% and then degreased on the inside by passing a commercially available degreasing agent through the tubes.
• Pipe sections cut to length and deburred to 300 mm were then subjected to oxidizing heat treatment in a laboratory furnace with circulated air as furnace atmosphere at 250 ° C. for a period of 30 minutes.
• the oxygen content (O2 content) of the copper oxide layer now formed on the inner surface of the tubes was determined by means of energy dispersive analysis (EDX) to 13.8%.
• test pipe sections were arranged vertically and filled with drinking water.
• the copper ion release was determined in a series of tests lasting several months.
• the amount of copper released in mg / l was measured in 24-hour intervals with an absorption spectrometer.
• the pH of the drinking water used was 7.6.
• the upper limit of the measured values for the copper content in drinking water was 1 mg / l.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=6499828

Family Applications (1)

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Cited By (6)

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Citations (6)

• 1993
  • 1993-10-09 DE DE19934334536 patent/DE4334536A1/de not_active Withdrawn
• 1994
  • 1994-09-13 DK DK94114354T patent/DK0647723T3/da active
  • 1994-09-13 DE DE59409284T patent/DE59409284D1/de not_active Expired - Fee Related
  • 1994-09-13 ES ES94114354T patent/ES2144475T3/es not_active Expired - Lifetime
  • 1994-09-13 EP EP19940114354 patent/EP0647723B1/fr not_active Expired - Lifetime

Patent Citations (6)

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