CS239025B1 - Punch-mandrel alloy with increased resistance to hot wear - Google Patents

Abstract

Alloy intended for the production of punching mandrels used in the production of seamless steel pipes. In addition to iron and the usual impurities, it contains 0.2 to 0.4% carbon, 0.2 to 0.7% manganese, 0.2 to 0.8% silicon, phosphorus max. 0.035% max. 0.04% sulfur, 0.6 to 1.4% iron, 3.0 to 7.0% nickel, 0.01 to 2.5% molybdenum, 0.001 to 0.02% boron -and 0.001 to 0.07% aluminum, all expressed as percentages by weight.

Description

The invention ae. alloys for the production of punching mandrels used in the manufacture of seamless steel tubes.

In the manufacture of seamless steel tubes, the first deformation operation of punching the heated billets is the mandrel of the punching machine. The punched, water-cooled mandrels with a spray of water in the dark carrier are subject to high temperatures during this process, as the billets have a temperature of about 1250 ° C. A portion of the mandrel is heated to a temperature of 800 to 900 ° C over a period of 15 to 30 seconds, and again cooled to a temperature of 200 to 300 ° C over a period of 15 to 30 seconds, and thus subjected to very high thermal shocks. Due to this thermal cyclic stress, the alloyed alloys used to make the punch mandrels are susceptible to cracking and at the same time have a relatively high coefficient of friction so that the mandrels wear very quickly. In this way, the adjustment of the punching table is constantly changing with the positioning of the punching mandrel, which affects the quality of the punching. Wear deteriorates the quality of the inner surface of the tubes produced, which therefore requires frequent replacement of the punch mandrels, the high consumption of which negatively affects the cost item of the production process.

These drawbacks of the known alloys used for casting or forging of punching mandrels are overcome by the hot-wear punching alloy according to the invention, characterized in that the alloy contains 0.2 to 0.4% carbon in addition to iron and common impurities. 2 to 0.7% manganese;

0.2 to 0.8% of silicon, phosphorus phosphorus αχ 0.035%> sulfur 0.04 0.6 to 1.4% chromium; 3.0 to 7.0% nickel; 0.61 to 2.5% molybdenum; 0.001 to 0.02% boron and 0.001 to aluminum, all by weight *.

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The casting alloy according to the invention has advantages over the prior art by substantially increasing the life of the punch mandrels due to its good heat abrasion resistance, thermal shock resistance and low friction coefficient at high temperatures. The extended life of such mandrels guarantees a satisfactory punching function in which neither the surface nor the profile of the mandrel substantially changes over its entire life. This effect is an important prerequisite for automating punching, increasing the productivity of the rolling mill and improving the inner surface quality of the tubes.

The principles of the invention and the effects achieved are illustrated by the following examples:

Example 1

Alloy steel with chemical composition was melted in electric furnace: carbon 0,3%} manganese 0,3% »silicon 0,5% i phosphorus less than 0,035 sulfur less than 0,04%} chromium 1,0 nickel 4» 5 molybdenum 0.01%} boron 0.010% and aluminum 0.02%, all by weight. Punching mandrels with a diameter of 95 mm were produced from this alloy by casting in sand molds for the production of seamless steel tubes on a Stiefel rolling mill. The punches were heated to 820 ° C in a heat treatment, held at this temperature for 2 hours, and then cooled in air. The darkness thus produced withstood 689 rolling cycles.

Example 2

Manufacturing technology and heat treatment identical to the first example produced punched mandrels of alloy with alternative chemical composition, expressed in terms of weight of elements: carbon 0,3% »manganese 0,3 silicon 0,5 phosphorus less than 0,0035%> sulfur less than 0.04 chromium 1.0 nickel 5.0 molybdenum 2.0 boron 0.005% and aluminum 0.02%. These mandrels showed a service life of 711 rolling cycles.

These and other in-service tests show that, compared to the previously recorded service life of about 170 rolling cycles, the service life of punched mandrels made of the alloy of the invention ranges from 500 to 600 rolling cycles in normal operation.

Claims (1)

Punch mandrel alloy with increased heat wear resistance for punch mandrel production, characterized in that it contains 0.2 to 0.4% by weight of carbon in addition to iron and usual accompanying impurities; 0.2 to 0.7% manganese; 0.2 to 0.8% silicon; jTÉcyy 0.035% phosphorus; 0.04% sulfur; 0.6 to 1.4% of chromium; 3.0 to 7.0% nickel; 0.01 to 2.5% molybdenum; 0.001 to 0.02% boron and 0.001 to 0.07% aluminum.