Tubes and plate-mounted molds for CCM

Working member of molds is one of the most essential parts in the continuous casting process of the metallurgical production

Over the last decades effectiveness of continuous casting machine (CCM) operation has been one of the basic indices of the ferrous metallurgy engineering performance level. The mold is the most critical and important functional assembly of the continuous casting machines. It serves for heat extraction during incrusting metal crystallization and ingot formation. This assembly determines efficient CCM operation, its performance and quality of the continuous ingot obtained.

The mold is an assembly consisting of the copper tube or built-up copper plates’ structure where metal crystallization takes place, and steel body that clamps the copper working member and has flowing cooling water clearance for efficient water extraction.

CCM molds are functioning in the environment of cyclic intensive heat flows, intensive wear, cyclic thermodynamic stresses and various types of erosion in the temperature range 293…683 K. Service life of molds is much shorter that that of other replaceable parts. Failures result in downtime, production accidents, and affect ecological and labor safety. Accordingly, extension of the service life of mold working member at high casting rate is an extremely important and crucial task, in particular, when casting small section ingots with edge size up to 6-8 mm.

Presently, tubes or mold built-up structures on the basis of plates are used as mold working section. In both versions the working section is made of refined copper or various alloys with silver, chromium and zirconium. In order to enhance performance properties and service life the inner surface of the mold working section is coated with special nickel- or chromium-based protective coatings. In some critical instances three-layer coatings can be used, like nickel-cobalt-chromium, enhancing performance characteristics, but dramatically increasing manufacturing cost. The mold working section protective coating is usually 0.12 – 0.22 mm, and it serves for reduction of melted metal friction with mold working section and reduction of metal adherence when starting up CCM.

Tubular molds

The molds with tube as a working element are most widespread in the continuous steel casting technology. Tubular molds are effectively used for casting square section billets with edge size up to 250 mm and round blanks with diameter up to 250 – 270 mm. With high heat transfer efficiency and correspondingly intensive heat extraction throughout the length of the mold, the tubes may have working length up to 1,200 mm. Meanwhile, tubes with parabolic profile or multi-stage tubes with tapered surface are usually used. Correct calculation of tube shape and its angle of taper are crucially important for obtaining minimal clearance between the mold tube wall and continuous ingot crust, which while moving inside the tube and under intensive cooling undergoes constant natural shrinkage and reduction of section.

Major advantages of use of tubular molds:

• low specific production costs;
• high quality of casting surface due to absence of joints in the working element with rapid and uniform growth of hard crust;
• high steel casting rate through high heat extraction intensity making it possible to cast steel at higher rate;
• less labor-intensive technology of working element replacement;
• high service durability of the tube with service life can reach 15 – 25 thousand tons of cast steel.

Plate-mounted molds

Plate-mounted molds are used for bloom and slab CCM and can be of box or fan design. The fan type of the plate-mounted mold is usually used for bloom continuous casting machines. Plate-mounted molds are formed of thick copper plates. Unlike tubular molds, thickness of the plate-mounted mold wall is substantially larger and can reach 60-80 mm. Inside plates, representing the mold body, special ducts in the form of openings with diameter of 20 mm and spacing between openings of 30-40 mm are arranged. Minimal distance between working surface and cooling ducts is 10 mm. There is also a variety of plates with longitudinal rectangular ducts (15 mm – width, 5 mm – depth) running along the length of plates’ external surface. The length of the working surface of plate-mounted mold is similar to its tubular analogues and equals to 700 – 1,200 mm.

The plate-mounted structure makes it possible to change slab or bloom width during the casting process, and also change the angle of the taper in side edges. In case clean copper plates are used after certain wear of the inside surface the plates are rearranged, thus making it possible to use them for up to 5-6 cycles. There are also plate-mounted structures used for slab molds with possibility of side wall shift in order to change the width of cast slab and correct the angle of the taper in side edges.

Main characteristic:

Casting radius: R4,000~R12,000 мм

Ingot size: 100x100~160x280~200x400 мм

Cooling jacket: one-piece or stainless steel divided into segments

Water flow: 4 mm (may vary depending on different specifications of copper tubes of molds)

Hydraulic pressure: over 1.0 MPa

Coolant flow rate: 10-16 m/s

LCC "INTECH GmbH" exercises control over operation of all assemblies in manufacture of mold working elements, starting from melting and casting process, hot extrusion and hot pressing, cold drawing and ending up with machining equipment.

Fabrication of the mold copper tube starts with casting of an alloy with the set parameters of chemical composition. For effective control of added elements initial components undergo preliminary chemical analysis. Melted material is poured in special round section ingots and then subjected to pressing and stamping. After cold drawing and heating cycles arc-shaped conical tube is obtained, subjected to drawing. The drawing is the most critical process affecting quality of the final product.

In order to provide the required accuracy of the tube inner section narrowing special tooling is used designed for each type of copper tubes. Then after machining the inner surface of the mold tube is coated with coating having preset composition. At the final production step the product undergoes strict quality control, with test report enclosed with delivered article.

In the aggregate, strict observance of all production process requirements guarantees high quality of our products and on time production and delivery.

Specialists of LCC "INTECH GmbH" are ready upon customer’s request to visit his production site and make measurements of dimensions, coating thickness and strength characteristics of mold tubes being used, develop working drawings and deliver in-house tubes with improved parameters at optimal cost. The company’s employees have gained successful experience of such deliveries with customers’ positive references.

Engineering Company LCC "INTECH GmbH" is also ready to deliver to metallurgical production customers a number of special parts fabricated of special stainless steels having enhanced mechanical durability and wear resistance, heat-resistant steels, satellites, bronze, ceramics and coated steels under customers’ requirements specifications:

• Rolls for cold and hot rolling mills
• Spindles and cardan shafts of rolling mills,
• Toothed wheels, gear shafts, gerotors, worm-and-worm gears, conical and globoid gears,
• Special products from bronze, including those used during stainless steel extrusion
• Furnace rolls, including those with special coating,
• Submersible equipment made of stellen and ceramics for hot dip galvanizing of stainless steel strip and parts.

As per drawing:

Chemical composition of product offered

Technical characteristics of CCM mold tubes

As per drawing:

Chemical composition of material of product offered

Technical characteristics of CCM mold tubes