SK544190A3 - Knife for meat mincing and mixing machines - Google Patents

Abstract

Steel for the production of knives for meat disintegrating and mixing machines contaigns 0.7 - 0.9 wt.% of C, less than 1 wt.% of Si, less than 1 wt.% of Mn, 0.5 - 1.5 wt.% of Mo, 0.7 - 0.95 wt.% of V, 0.3 - 0.9 wt.% of Nb, 12.1 - 13.9 wt.% of Cr, remainder Fe is used for cutting knives for cutting meat.

Description

Technical field

The present invention relates to martensitic chromium steel, which is high-strength, tough and corrosion-resistant, for the manufacture of knives for crushing and mixing machines for meat.

Such knives are mainly used for cutting meat. In particular, steel suitable for such knives must have a certain spectrum of properties. Such a spectrum includes, in particular, corrosion resistance from the exposure to tissue fluids, substantially saline solutions resulting from meat cutting, high hardness to ensure blade durability, high strength, withstands centrifugal forces at high speeds of about 4,000 rpm, good abrasion resistance in order to achieve large time intervals between grinding, satisfactory toughness, so that it is also possible to cut harder, for example, deep-frozen pieces, good polishability to ensure good optical appearance and, finally, to be produced as low as possible.

From such 0.2 to the prior art

DE-PS 1 59 794 has long been known to use martensitic corrosion resistant chrome steel with 2.5 wt. % carbon, 8 to 22 wt. % of chromium, as well as the usual contents of manganese, silicon, phosphorus, sulfur and nitrogen, as well as 0.2 to 6 wt. % molybdenum and / or tungsten. An example is steel with about 1 wt. % carbon, 0.5 wt. % manganese, 0.24 wt. % silicon, 13 wt. % chromium, 1 wt. % molybdenum and 0.14 wt. % nitrogen. Similarly composite steels for cutting tools with additional contents of carbide forming elements such as vanadium, titanium, tantalum, niobium and zirconium, in total amounts up to 2 wt. % are known from DE-AS 17 52 655. An example is steel with 0.6 wt. % carbon, 1 wt. % silicon, 0.36 wt. % manganese, 10.5 wt. % chromium and 1 wt. % molybdenum. This known steel contains at least 20 wt. % residual austenite.

DE-OS 33 39 904 discloses a special layer for knives for meat-kneading and mixing machines for meat, in which either a hard middle layer between two tough layers or a tough middle layer between two hard layers is provided. interconnected by composite rolling. Steels with a relatively high chromium content, for example 14 or 18 wt. % chromium. The tough layer has a relatively low carbon content of about 0.1 wt. %. The carbon content of the hard layer has a value of about 1 wt. %. In addition to the usual silicon and manganese content below one weight percent, these steels may each contain 1 to 2 wt. % molybdenum and 1 to 2 wt. % vanadium.

The essence of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide steel for knives for meat chopping and mixing machines which, in view of the above-mentioned spectrum of properties, have optimal values at favorable production costs.

According to the invention, this object is achieved by a martensitic steel consisting of

0.7 to 0.9 wt. % carbon, less than 1 wt. % silicon, less than 1 wt. % manganese,

0.5 to 1.5 wt. % molybdenum, 0.7 to 0.95 wt. % vanadium, 0.3 to 0.9 wt. % niobium 12.1 to 13.9 wt. % of the chromium, the balance being iron, including impurities due to melting.

Steel from this region with about 0.80 wt. % carbon, 0.50 wt. % silicon, 0.45 wt. % manganese, 13.0 wt. % chromium, 1.3 wt. % molybdenum, 0.90 wt. % vanadium and 0.70 wt. % niobium has proven particularly useful for such knives. The reason for this is that the steel used according to the invention has an excellent corrosion resistance compared to the steel used up to now, the material number 1.4153 on account of its higher molybdenum content and the grain-refining effect of niobium. In addition, the niobium primary carbides precipitated in fine form together with the secondary carbides eliminated in tempering ensure high abrasion resistance.

Overview of the figures in the drawing

In FIG. 1 is a diagram showing the Rockwell HRC hardness curve during the tempering temperature at ⁰ ° C and a diagram showing the bending toughness curve in J / cm ² during the tempering temperature at ⁰ ° C.

DETAILED DESCRIPTION OF THE INVENTION

The steel is produced by a conventional melt metallurgical process. Hot and subsequently cold rolled strips are processed into knives. After austenitizing at 1050 to 1100 ° C to form a martensitic variable structure from the curing temperature, the blades are rapidly cooled and then tempered at temperatures of 460 to 560 ° C to achieve optimum hardness, toughness and corrosion resistance.

Then, the properties listed below are achieved.

With roughly the same hardness according to the invention, the steel used, due to its finer and more uniform carbide formation, achieves a toughness 15 to 25% higher than that shown in FIG. 1. Long-term experiments have shown a 50% higher permanent fatigue limit at oscillating stresses, which makes it possible to significantly increase the resistance of highly stressed knives of this type. In the salt spray test, the steel of the invention produced a significantly less corrosion attack than that of a comparable steel, material number 1.4153.

In FIG. 1 shows the Rockwell HRC hardness curve over a tempering temperature of ⁰ DEG C. in the upper diagram, the tempering time being two hours. By means of the upper curve, in the upper diagram in FIG. The hardness profile of the steel for the crushing and mixing machines according to the invention is shown, while the lower curve shows the hardness profile corresponding to the steel Material number 1.4153.

In the bottom diagram of FIG. 1 shows the course of bending toughness in J ' cm < ^{2 >} over a tempering temperature of ^{0 [} deg.] C., the tempering time being two hours. The upper curve shows the bending toughness in J / cm ² during the tempering temperature in ° C of the steel for the crushing and mixing machines according to the invention, while the lower curve shows the toughness profile corresponding to the material number 1.4153.

Claims (2)

PATENT CLAIMS 1. Knife for meat chopping and mixing machines made of martensitic chromium steel, characterized in that it consists of 0.7 to 0.9 wt. % carbon, less than 1 wt. % silicon, less than 1 wt. % manganese, 0.5 to 1.5 wt. % molybdenum, 0.7 to 0.95 wt. % vanadium, 0.3 to 0.9 wt. % niobium, 12.1 to 13.9 wt. % of the chromium, the balance being iron, including impurities due to melting. Knife according to claim 1, characterized in that it consists of 0.80 wt. % carbon, 0.50 wt. % silicon, 0.45 wt. % manganese, 13 wt. % chromium, 1.3 wt. % molybdenum, 0.90 wt. % vanadium and 0.70 wt. % niobium, the balance being iron.