HU199086B - Method for soldering in protective atmosphere alloyed chrome-nickel steel building units - Google Patents

Abstract

The invention relates to a method and a device for protective gas loosening of high-alloy Cr-Ni steel components. The aim of the invention is to allow a simple and reliable connection of such components under assembly conditions, wherein a separate chemical or mechanical pretreatment, which accounts for the oxide layer adhering to the metal soll.Erfindungsgemaess this is achieved in that the principle of direct electrical Resistance to warming to be heated Loetstelle is surrounded by a protective chamber. This arrangement is then pervaded by an inert gas during the warming-up phase and the subsequent cooling-off phase, which may have a maximum technical contamination of 100 vpm. The chamber volume must not exceed a maximum of 200 cm high 3, but it must be 20 to 30 times larger than the component volume involved in the soldering process.

Description

The present invention relates to a method for soldering alloyed Cr-Ni steel horse parts under mounting conditions, in particular for welding small diameter pipes.

The main problem in soldering alloyed Cr-Ni steels is the removal of the oxide layer adhered to the metal. This is done with known soldering methods using saline fluids. The disadvantage of this process is that after soldering, aggressive flux residues remain which corrode the material when exposed to moisture. The mechanical removal of such flux residues is very difficult and in some cases practically impossible.

If flux residues remain after careful chemical treatment of the soldering spot, this can later lead to severe material losses.

Because of the above difficulties, furnace soldering is often used, whereby the oxide layer is removed by vacuum or shielding gas. Shielding gases are either reducing gases (e.g. dry hydrogen or ammonia decomposition gas) or inert gases (e.g. argon with a total impurity content less than 10 ppm). Since Cr-Ni steels often contain other metals with high affinity for oxygen, such as titanium, an extremely dry shielding gas (dew point -70 ° C) should be used when using an inert gas.

In order to moisten the base metal, the surface must be carefully treated mechanically and chemically, leaving only a thin layer of oxide. At high soldering temperatures (1000 ° C), this oxide layer breaks and allows a proper connection between the solder and the parent metal. At the breakpoints of the oxide layer, the solder penetrates underneath the oxide layer, lifts it and inserts it in the soldering joint (Ziiniiierinann, KF: Mechanisiertes Hartlöten auf Lottvorrichtungeri und Lötmaschinen - Technische Fischerung, Schneiderfahrzeugtechnik, 25).

In the use of reducing gases, the .xidium layer is removed by the reducing components of the shielding gas, essentially hydrogen. The reducing effect is primarily due to the temperature and composition of the shielding gas. Difficult reducing metal oxides (e.g., chromium oxide) require virtually free of oxygen and oxygen-containing compounds, and are particularly dry. For this reason, dry hydrogen or dry ammonia glazing gas is generally used as the protective gas.

Another way to remove interfering oxide layers during soldering is to apply vacuum, which involves removing the oxide layer from the carbon-containing metal based on the relucing action of the carbon itself. The conditions for rapid reaction progress are improved by increasing the carbon content of the steel, decreasing the stability of the oxide to be reduced, and decreasing pressure in the vacuum furnace. Because the stability of the oxide depends on the temperature, the oxides

CO reaction temperature and pressure dependent, such as the chromium oxide has been reduced at 680 ° C from coal when the CO partial pressure is less than 10 ¹ Pa. The same reaction is also possible at 1000 ° C if the pressure is increased to 10 ³ Pu (Ogier maiin, G .: Zimmerrnann KF: Mechanist's Hartlöten auf Lötvorrichtungen und Lölinuschinen ... Technik die verbindet, Berichte aus Forschung und Praxis No. 26).

In carbonless metals, the oxide layer is either dissolved in hydrogen or cracked by heating, whereupon the liquid solder flows down, lifts it and integrates it into the bond , 249-254 (1969).

The procedures described have the following disadvantages:

“Due to expensive equipment, vacuum soldering cannot be used for continuous production.

- Reducing gases, which are primarily Lartal30 gaseous hydrogen, should be avoided as there is a high risk of explosion in the construction site.

Another known possibility of fitting Cr-Ni steels using inductive soldering is argon (Kaiser, L .: Inductors von Hochdruckrohrleitungen im Flug- und Raumfahrzeugbau, Schwieuen und Schneiden, 24, 5, 161-165 (1972)). Due to the costly heating equipment, this method is not applicable to continuous pond production, where the mechanical removal of the oxide layer and the high cost of shielding gas also adversely affect the economics of this fitting technology.

It is an object of the present invention to provide a method of joining alloyed Cr-Ni target building blocks which allows simple and reliable bonding even under mounting conditions.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for soldering Cr-Ni steel building elements alloyed with at least 1% by weight chromium and at least 1% by weight nickel which do not require special chemical or inechunical pre-treatment of the metal oxide bond.

This object according to the invention can be solved by surrounding the soldering point, which is heated at a temperature of at least 1000 ° C by the principle of direct electrical resistance heating, with a protective chamber. In this arrangement, at least 10 L / min of inert gas L, with a maximum technical impurity of 100 ppm, wet-23, is passed through the heating phase and the cooling phase.

HU 199086 may contain up to 35 ppm, up to 10 ppm oxygen, up to 10 ppm hydrogen and up to 1 ppm carbon dioxide.

The enclosure for soldering of alloyed Cr-Ni steel building blocks shall have a volume not exceeding 200 cm ³ . However, this volume of the chamber should be 20-30 times greater than the volume of the elements to be soldered. The inlet arrow for the injected gas in the shielding chamber is not more than 2-3 cm from the soldering position.

The invention is further illustrated by the following example.

Example

High-alloyed steel tubes (X8CrNiTi 18, 10), 12 x 2 mm, are soldered to each other along their longitudinal axis.

To do this, the soldering points are cleaned with a degreasing solvent and prepared as follows: Preambles · Draw a solder ring, eg CuMn 10 Co 3- 2, on each end of the tube and equilibrate with a gauge. Then, a soldering sleeve is pulled on one end of the tube and the other end of the tube is inserted into the same sleeve so that they touch each other. A soldering iron chamber is placed at the 3 places so prepared, with a viewing window at the top. The electrical contacts of the resistor soldering device are fastened to the tube to the left and to the left of the chamber, and at one end of the tubes to be soldered, 3 conduits for the injection of injected gas are secured inside the tube. The actuator is then rinsed with shielding gas (10 L / min) to keep air in the tube. At this point, the other end of the tube is sealed and the shielding gas is forced into the shielding gas chamber through the soldering gap. After the protective copper chamber has been flushed through the same gas stream through a separate conduit for about 30 seconds and the air has been expelled, the soldering process 4 can be started.

Oxidation fluxes during soldering break at temperatures above 1000 ° C. Soldering can only flow if metal reoxidation is prevented.

This is achieved by an internal shielding gas atrium, which may consist of argon or nitrogen, up to 100 ppm of technical impurities (argon: moisture 35 ppm, oxygen 8 ppm, methane 1 ppm: nitrogen 30 ppm, oxygen 1 ppm, carbon dioxide 1 ppm , 10 ppm hydrogen).

Under these conditions, the liquid solder gets underneath the ruptured oxide layer, lifts it, and integrates it into the solder joint. Soldering with the gases described is filled with a shielding gas chamber. Here, the chamber dimensions should be chosen so that the volume of the chamber does not exceed 200 ci, within which the specific chamber size is chosen to be 20-30 times, preferably 25 times larger than the volume of the source elements. The inlet of the shielding gas in the chamber should be only 2-3 cm away from the soldering point. This soldering place is heated by the principle of direct electric resistance heating, what! it is possible to ensure that the soldering point is heated for a short period of time and that the solder may become soldered. If the solder rings are melted along the entire circumference of c, heating can be completed. The soldering is then legalized! Cool under shielding gas for 30 seconds to avoid fraying.

The line and shield gas chamber are then live edged and any discoloration is removed with a cloth. Often used for soldering high-alloy steel building blocks; use nickel-based solder as a shield;

oven. It contains non-metallic alloys such as silicon skin or phosphorus to lower the solder melting point to 83 ° -1135 ° C. The consequence of this is that these elements form a coarse intermediate layer of iron, which, after the main dewatering, can only be eliminated by expensive diffusion heat. The lysis time is 1-5 hours depending on the amount of lithium, boron or phosphorus. For this reason, such a nickel base:

soldered soldering iron should not be used in the installation conditions of the customer.

The use of soldering fluids having a melting point slightly below 0 in the base metal melt is practically possible according to the invention, since the temperature can be controlled directly at the soldering site, thus avoiding melting point additives. The solder used in such an arrangement has the following composition:

0.1% T, C 1% Si, 0.60% Mn, 0.02% P

0.015 t% S, 19 t% Cr, 29 t% Ni, Fe remaining

The application of the high temperature solder according to the invention does not require diffusion glow. Because the base edges and for0 ras are of similar composition, the bond exhibits similar corrosion behavior to the parent metal.

Compared to the known process using liquid solder and flame, the degree of wetting is significantly improved and therefore fewer wetting errors are to be expected. The bond strength reaches that of the base material, so for the example X8CrNiTi 18.10 used, 500-700 N / nmA

Claims (2)

1. A method of soldering a high-temperature shielded gas of a Ci-Ni-acrylic alloy with at least 1% by weight of chromium and at least 1 by weight of nickel during assembly on site, characterized by heating the soldering point to a temperature of at least 1000 ° C. about 20 to 30 times the volume of the soldering element, but not more than 200 cm ³ , and through this with a flow rate of not more than 100 ppm of 15 technical impurities with a moisture content of not more than 10 ppm 35 ppm, oxygen up to 10 ppin, hydrogen up to 10 ppm and carbon dioxide content up to 20 1 ppm, and the inlet gas inlet is not more than 2-3 cm from the soldering position. 2. The process of claim 1, wherein 0-0.1% by weight of C, 1-1.25 IX Si, 0-25% -0.6 tX Mn 0-0.02 tX P, 0-0.0115 L% S, 15-25 tX Cr, 20-80 t% Ni and the remainder of the Fe are soldered.