SU747657A1 - Thermite mixture composition for welding cast iron - Google Patents

Description

The invention relates to the field of thermite welding, in particular, to compounds of thermite mixtures used mainly for cast iron welding. In welding production, thermite mixtures are widely known, containing aluminum, iron oxide and steel filler 1 as a base. Of the known thermite mixtures, the thermite powder for cast iron 2j containing the following components is closest to this composition, weight%: Aluminum65-75 Iron scale 15-25 Graphite7-15 The disadvantage of this composition is that when welding and welding defects, cast alloy of cast iron For example, alloyed with chromium and nickel, the metal deposited by it does not contain alloying elements and differs dramatically in chemical, composition, structure, wear resistance, heat resistance, corrosion resistance and mechanical properties from the base metal. but. This reduces the reliability of the welds of castings during operation. Note that other known thermite mixtures, including ferroalloys containing as alloying additives, are not sufficiently effective in this respect. First, the introduction of additives such as ferrochrome, granular nickel, etc. into the thermite mixture. reduces the content of active components in aluminum (aluminum and iron oxide) and, accordingly, the thermal effect of thermite reaction. Secondly, the melting of these refractory additives consumes a significant portion of the heat generated during the thermite reaction, which causes the possibility of irregularities, tops, local friability, chemical heterogeneity and other defects in the laziness in the weld metal. In addition, during the welding process, partial oxidation is observed, burnout and the transition into the slag of these alloying elements, due to which their content in the weld metal is usually reduced. Due to the fact that in thermite mixtures of known compounds there are no modifying and remodeling additives, the difference in structure and properties between the weld metal and the base metal is especially great when welding modified gray cast iron (MG4) and high-strength nodular cast iron () „

It is not uncommon to observe chipping of the deposited metal and the presence of cementite inclusions in the structure during the welding of gray iron castings; sword, the formation of cementite, plastic and mixed graphite instead of: spherical graphite when welding from cast iron from high-strength cast iron CHIGG. : In a number of cases it is difficult for the mechanical; Česk treatment of the welds after welding, as well as in the welds and the heat affected zone, stresses and cracks may occur.

The purpose of the invention is to improve the physicomechanical properties of the weld metal and simultaneously increase the heat generation during the welding process.

To achieve this goal, chromium oxide, nickel oxide, cryolite, a component selected from the group, are additionally introduced into the thermite mixture of a known composition containing aluminum, iron oxide, graphite; cerium, thorium and lanthanum, magnesium-calcium iron-silicon ligature. In this case, the content of all the above ingredients should be in the following ratios, wt.%:

Aluminum 20-26

Graphite4-8

Cryolite - 0.8-4.0 Chromium Oxide2-14

Nickel oxide 2-15

Magnesium calcium iron-silicon 0.7-3.5

ligature

Component selected from the group: cerium, thorium, lanthanum 0.05-0.1 Iron oxide Rest Example. Compared ;; with a tertiary powder of known composition, three thermite mixtures were made: mixtures A and B with a boundary content of components and mixture C of an intermediate composition that is close to optimal.

The composition of the mixture is A, wt.%: Aluminum20, graphite-8, cryolite-4, chromium oxide14, nickel oxide -15, magnesium-calcium iron-silicon ligature-3, 5, cerium-0, 1 and iron scale-35.4.

The composition of the mixture B, wt.%: Aluminum-2 € graphite-4, cryolite-0.8, chromium oxide-2 nickel oxide-2, magnesium-calcium-iron-silicon ligature-0.7, cerium-0.05 and iron dross-64,45,

The composition of mixture C, wt.%: Aluminum-2 graphite-6, cryolite-2.4, chromium oxide-8, nickel oxide -8.5, magnesium-calcium-iron-silicon ligature-2.1, cerium, 075 and iron dross-49.025.

The table gives the characteristics of the known and indicated mixtures.

As can be seen from the table, termite dares of known composition can be used only for welding unalloyed and unmodified iron.

Introduction to the proposed thermite mixtures of chromium oxide and nickel oxide not only increases their oxygen balance and increase heat generation, but also ensures that the thermite metal is doped with chromium and nickel when they are. in the recovery of oxides on the corresponding exothermic reaction

Qi m with aluminum,: S. without ferroalloy. At the same time, by changing the content of chromium oxides and nickel oxides and the ratio between them in the mixture, it is possible to regulate the concentrations of chromium and nickel in the weld metal.

Claims (2)

When using the mixture In cyNEviapnaya content of chromium and nickel in the weld metal is small (2.6%) ,. which indicates the feasibility of its use for welding high-strength cast iron SCH-24-44, SCH-28-48 and. some heat-resistant cast irons (for example, casting for casting, retorts, cementation pots, etc.) Mixture A provides the highest total content of chromium and nickel in the weld metal (19.1%) and is mainly suitable for welding castings from high-alloyed corrosion resistant cast irons, for example, for chemical engineering. When welding cast irons with low and medium chromium and nickel contents, composition A should be additionally introduced into an iron aperture. Mixture C is more versatile and has the best marking coefficient. It can be recommended for welding a wide range of castings from copper and non-alloyed cast iron. From the table it can be seen that the mixture of B is optimal in terms of heat generation. The great advantage of this thermite mixture in comparison with the known one is that it can be used in welding high-strength nodular cast iron with graphite. At the same time, as a modifier in the mixture, enter a ligature containing 6% magnesium, 57% silicon, 22% calcium, and 15% iron. The use of a modifier in the form of a ligature in comparison with the introduction of separate modifying additives of magnesium, ferrosicyles, silicocalcium, etc. into the mixture. provides a more uniform assimilation of the modifier by the volume of the weld metal and increases the effect of graphite spheroidization. In addition, to eliminate the influence of demodifying factors (excess magnesium, aluminum, sulfur, etc.), a component selected from the group: cerium, thorium, lanthanum in an amount of 0.05-0.1% is introduced into the mixture. It is also significant that the thermoenna terman mixture provides a reduction in the costs associated with welding, since the alloying of the weld metal with chromium and nickel is achieved without the inclusion of ferrous alloys. The invention The composition of the thermite mixture for welding cast iron, containing aluminum, graphite and iron oxide, is the fact that, in order to improve the physical and mechanical properties of the weld metal, it additionally contains cryolite, chromium oxide, oxide Nickel, a component selected from the group; cerium, thorium and lanthanum, magnesium-calcium-iron-silicon ligature, with the following ratio of components, bc%: Aluminum 20-26 Graphite 4-8 Cryolite 0.8-4 Chromium oxide 2-14 Nickel oxide 2-15 Component selected from groups: cerium, thorium and lanthanum 0.05-0.1 Magnesium-calcium-iron-silicon ligature 0.7-3.5 Iron oxide Else Sources of information taken into account during the examination 1.Naumenko V. S. Thermite welding of rails, M., Ed. Trinity literature, 1969, 66-8. 2. Authors certificate of the USSR 508362, cl. In 23 K 23/00, 1973 (pro.totip).