RU2722844C1 - Method for production of cast multilayer workpiece - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates to production of cast multilayer billet of high alloyed steel. Core is made, the ingot is heated and cast, the concentric layer of metal is applied on the core, after which the workpiece is subjected to hot deformation. Core used is pre-melted and prepared rod, casting of multilayer workpiece is performed by casting metal into mould with pre-installed heated rod. Rod is preliminarily chemically cleaned by etching in a bath with an alkaline solution at the following ratio: NaOH 40÷45 %; NaNO30÷35 %; NaCl 10÷15 % and NaCOis the rest, at temperature 400÷450 °C for 20÷30 minutes, then washed first in hot water at temperature of 70÷80 °C for 5÷7 minutes, then in cold water and dried in a drying chamber at temperature of 100÷110 °C.EFFECT: broader technological capabilities.1 cl, 1 dwg, 2 tbl

Description

1. The technical field

The invention relates to the field of special metallurgy, and in particular to a method for the production of cast multilayer billets from high alloy steels and corrosion-resistant alloys, for further hot processing, for the manufacture of products (bar, wire, sheet or tape).

2. The prior art

The well-known "Method of producing three-layer sheets and strips" (Patent RU No. 2014190, (B23K 20/00), 1992), including the preparation of a three-layer blank by surfacing of a clad layer of corrosion-resistant chromium-nickel steel of austenitic class on the blank of the main layer of carbon or low alloy steel and subsequent rolling blanks. The disadvantages of the method include high labor costs.

The known "Method of manufacturing a layered material" (Patent RU No. 2267550, (C22F 1/18), 2002) comprising plastic deformation of a zirconium alloy preform, which is carried out in at least two directions, and deformation in one direction does not exceed deformation in the other direction less than three times, and the algebraic sum of deformations in all directions is not less than 250%. After deformation, the zirconium alloy preform can be further annealed in a vacuum furnace at temperatures up to 600 ° C. The disadvantage is that the process is not optimized for objects from high alloy steels and corrosion-resistant alloys.

The well-known "Method for producing composite material titanium-steel" (Patent RU No. 2293004, (C22F 1/18), 2002) including explosion welding and hot rolling of a welded three-layer package. The disadvantages of the method include dangerous and harmful production factors, and a high probability of the formation of an inhomogeneous wavy interface between the layers of the base and cladding, which may be unacceptable for some applications.

The well-known "Method for producing a consumable electrode of electroslag remelting for forming a multilayer casting" (Patent RU No. 2674596, (С22В 9/18, B22D 7/02, Н05В 7/07), 2017) comprising forming a multilayer casting by placing the molds heated to temperature 600-700 ° C metal plates in layers of molten metal. In this case, metal plates and molten metal have a different chemical composition. The disadvantage of this method is not the possibility of its application for the formation in the electrode of vertical layers of different chemical composition.

It is also known, accepted by the authors as the closest analogue, “Method for producing a multilayer wire” (Patent RU No. 2557378, (B32B 15/02, B32B 15/01, C22C 1/02, C22F 1/04), 2013). including the stage of manufacturing the core, heating and casting the ingot, applying at least one concentric layer of metal, pressing and drawing on the wire. The disadvantage of this method is the inability to use for high alloy steels and corrosion-resistant alloys.

3. The invention

3.1. Statement of the technical problem

The objective of the invention is to obtain a cast multilayer billet of high alloy steels and corrosion-resistant alloys, for a further redistribution, for the manufacture of products (bar, wire, sheet or tape).

The result of solving a technical problem

The solution of the technical problem is achieved by the fact that the smelting and casting of a multilayer workpiece is carried out in a mold in which a heated, pre-melted and prepared (forged or cast) rod is installed, after which the resulting workpiece is subjected to hot redistribution for the manufacture of products (bar, wire, sheet or tape).

3.2. Features

In contrast to the known technical solution for producing cast multilayer billets for manufacturing products, including the stage of core production, heating and casting of the ingot, applying at least one concentric layer of metal, pressing and drawing on the wire, the proposed technical solution uses pre-melted and prepared rod, casting of a multilayer workpiece is carried out by pouring metal into the mold with a pre-installed, heated rod, while the thickness of the layers is controlled by the distance between the mold wall and the surface of the installed rod, after which hot deformation is performed.

The preparation of the rod (forged or cast) is carried out through the smelting, casting of the electrode and subsequent machining. The forging of the electrode on a strip or round profile is carried out in accordance with the calculated rod sizes ня 90 × 100 mm or ∅ 80 ÷ 120 mm.

The surface of the prepared rod is degreased by etching in a bath with an alkaline solution at a temperature of 400 ÷ 450 ° C for 20 ÷ 30 minutes. Then the washing is carried out first in hot water at a temperature of 70 ÷ 80 ° C for 5-7 minutes, then in cold and drying is carried out in a drying chamber at a temperature of 100 ÷ 110 ° C. The composition of the alkaline solution used: NaOH - 40 ÷ 45%; NaNO ₃ - 30 ÷ 35%; NaCl - 10 ÷ 15% and Na ₂ CO ₃ - the rest.

Installation of the prepared rod in the mold is carried out vertically, along the axis of symmetry, preheated to the highest possible temperature (depending on the grade of steel or alloy), excluding the formation of scale.

The required thickness of the layers of the multilayer workpiece is controlled by the distance between the wall of the mold and the surface of the installed rod, which is suspended in the mold using a metal shaped rod (preferably a semicircle section) through the through hole in the prepared shank.

Smelting of metal (different from the composition of the core) and casting into the prepared mold with a cross section of 300 ÷ 500 mm of a round or square profile, with the core pre-installed in it, is carried out by any method (siphon, or from above), with a casting speed of 50 ÷ 180 sec and jet protection argon at a metal temperature in the bucket after purging with argon about 1540 ÷ 1620 ° C.

Further deformation of the multilayer preform is carried out in one or more redistribution with subsequent receipt of products from it.

3.3. List of drawings

In FIG. 1 is a diagram of a prepared mold with an installed rod, where 1. - Prepared forged or cast rod; 2. - The mold; 3. - Insulated extension; 4. - Refractory material; 5. - A through hole in the shank for installing the rod in the mold; 6. - Metal profiled bar (with a semicircle section); 7. - Axle; 8. - The hole for installing the cup or plug (cork), depending on the method of casting.

4. Description of the invention

In the claimed technical solution, at the stage of preparing for the assembly of the mold, for casting the multilayer workpiece, the rod (1) is preliminarily prepared, it is heated and installed in the mold (2), then the smelting and casting of metal (other than the composition of the rod) into the mold is done by siphon , or from above, after which the resulting multilayer billet is subjected to hot redistribution, while the following operations are performed sequentially:

- smelting of the electrode in an induction or open arc (alternating or direct current) furnace, sequentially adding alloying components and / or alloys and casting the metal from above using argon. The temperature of the metal in the ladle before casting should be in the range of 1540 ÷ 1620 ° C, the casting speed of 50 ÷ 130 sec and the exposure time in the mold for at least 6 hours;

- preparing the surface of the melted electrode by machining to a depth of 8-10% of the diameter, to remove surface defects;

- forging a pre-melted electrode onto a strip or round profile, in accordance with the calculated rod dimensions ≠ 90 × 100 mm or ∅ 80 ÷ 120 mm;

- machining the surface of the rod and cutting the shank, from the side of the head end, which provides for the through hole (5) for installing the rod in the mold. In the case of obtaining a cast electrode ∅ 90-110 mm, after machining the surface (by 8-10% of the diameter), a shank is cut from the side of the head end;

- to improve the weldability of the rod with the metal (different from the composition of the rod) and reduce the likelihood of internal delamination during subsequent hot deformation, the surface of the rod is degreased by etching in a bath with an alkaline solution at a temperature of 400 ÷ 450 ° C for 20 ÷ 30 minutes. Then, washing is carried out first in hot water at a temperature of 70 ÷ 80 ° C for 5-7 minutes, then in cold and drying is carried out in a drying chamber at a temperature of 100 ÷ 110 ° C. The composition of the alkaline solution used: NaOH - 40 ÷ 45%; NaNO ₃ - 30 ÷ 35%; NaCl - 10 ÷ 15% and Na ₂ CO ₃ - the rest;

- heating the rod (before installation in the mold) in a heating furnace to the maximum possible temperature (depending on the grade of steel or alloy), excluding the formation of scale;

- assembly of the mold and vertical installation of the rod, along the axis of symmetry of the mold, using a shaped metal rod (6) (preferably a semicircle section), through the through hole in the prepared shank (5). In this case, the thickness of the layers of the multilayer workpiece is adjusted by the gap between the mold wall and the surface of the suspended rod. The height of the suspension of the rod in the mold should not be more than 70 mm, otherwise it will lead to an increase in the amount of waste in the workpiece or rolling due to the one-component composition of the metal;

- smelting and casting of metal (other than the composition of the rod) with argon protection of the jet into the prepared mold in any way (siphon, or from above), with a casting speed of 50 ÷ 180 sec, at its temperature in the ladle after purging with argon of the order of 1540 ÷ 1620 ° C and subsequent exposure to the mold for at least 6 hours;

- further hot redistribution of the multilayer preform for the manufacture of products, for example:

- sheet production: forging in a press on a workpiece ≠ 65 × 330 mm, cutting on a hot cutting machine for measured lengths, processing of sutures and rolling on sheets of 9 ÷ 14 × 620 × 800 ÷ 1900 mm in size;

- wire production: forging on a radial forging machine or press on a workpiece of ∅ 95 mm, surface treatment and rolling for a size of ∅ 8 mm.

Using the proposed method allows to obtain a cast multilayer billet with a cross section of 300 ÷ 500 mm round or square profile for further hot processing using traditional metallurgical technologies.

5. An example of a specific implementation

Fulfillment of orders for Sv-10Kh19N23G2M5FAT steel wire is problematic due to the difficulty of meeting the requirements for the titanium and nitrogen content in the traditional smelting method. To solve this problem, a method of manufacturing a cast multilayer billet was implemented.

For the production of a forged rod in a steel mill in 1.0 tons of an induction furnace, smelting of high-alloy steel Sv-10Kh19N23G2M5FAT with a high titanium content was smelted and cast into a circular mold weighing 600 kg. The chemical composition of the heat is presented in table 1.

After the final solidification of the metal, the electrode was machined to a depth of 8-10% of the diameter, until surface defects were removed, and forged to a workpiece of ∅ 95 mm about 6 m long. Then, the workpiece was cut into 4 equal parts, the surface of each of which was machined and , from the side of the front ends, cut shanks with through holes for installing rods in the molds.

To improve the weldability of forged rods with cast metal and to reduce the likelihood of internal delamination during subsequent hot deformation, their surface was degreased by etching in a bath with an alkaline solution: NaOH - 40 ÷ 45%; NaNO ₃ - 30 ÷ 35%; NaCl - 10 ÷ 15% and Na ₂ CO ₃ - the rest. Etching was carried out at a temperature of 400 ÷ 450 ° C for 20 ÷ 30 minutes, then rinsed first in hot water at a temperature of 70 ÷ 80 ° C for 5-7 minutes, then in cold and dried in a drying chamber at a temperature of 100 ÷ 110 ° C.

Before installation in the molds, the rods were heated in a heating furnace to a temperature of 600 ° C.

Smelting of Sv-10Kh19N23G2M5FAT steel was carried out without the use of titanium-containing wastes, doped with nitrogen, mainly nitrated with ferrochrome, into liquid metal at the end of the melting period, followed by the oxidation of slag with borcal in an amount of 6-8 kg / t. The casting was performed by siphoning into the molds with installed, prefabricated, forged rods that were suspended vertically, along the axis of symmetry, in the center of the molds, so that the height of the rod suspension in the mold was 60 mm. The chemical composition of the smelted metal is presented in table 2.

The ingots after unloading from the ingot molds had a satisfactory surface with a slight rowidity from inversion in some places. Abrasive cleaning of defective places was carried out on the machine SH7-40.

Further, for the manufacture of wire, a hot redistribution of the multilayer workpiece was carried out on a radial forging machine to a workpiece of ∅ 95 mm, and after processing its surface, it was rolled at a mill of / 350/250 на 8 mm.

The finished wire consists of a rod with a high titanium content and an outer, uniform layer with a high nitrogen content, which is necessary to protect the arc zone when welding parts. Nitrogen protects against the formation of slag growths and strong oxidation, reduces toughness, increases the strength and temperature of transition of the weld metal to a brittle state, and causes aging of the joints. Alloying the weld pool with titanium allows you to achieve the optimal structure and high mechanical properties of the weld metal.

Thus, the use of the proposed method allows to obtain a cast multilayer billet with a cross section of 300 ÷ 500 mm round or square profile for further hot processing using traditional metallurgical technologies.

Claims (1)

A method of manufacturing a cast multilayer billet of high alloy steel, including manufacturing a core, heating and casting an ingot with applying at least one concentric layer of metal on the core, characterized in that the core is pre-melted and prepared, the casting of the multilayer billet is carried out by pouring metal a mold with a pre-installed heated rod, which is chemically cleaned by etching in a bath with an alkaline solution in the ratio: NaOH 40 ÷ 45%; NaNO ₃ 30 ÷ 35%; NaCl 10 ÷ 15% and Na ₂ CO ₃ - the rest, at a temperature of 400 ÷ 450 ° C for 20 ÷ 30 minutes, then washed first in hot water at a temperature of 70 ÷ 80 ° C for 5 ÷ 7 minutes, then in cold water and dried in a drying chamber at a temperature of 100 ÷ 110 ° C, while the thickness of the mentioned metal layers is controlled by the distance between the wall of the mold and the surface of the installed rod, after which the workpiece is hot deformed.

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