HRP20151160B1 - Metal bands and method of their producing - Google Patents

Abstract

The invention relates to a metal strip, which in addition to Fe additionally contains 0.01% - 0.2% C, 12% - 17% Cr, 4% - 8% Ni, ≤ 3.5% Cu, ≤ 0.5% Ti, ≤ 1,8% Si and ≤ 2% Mn and to the process of production of such strips through steps: <BR/> - preparation of metal material for strips with predetermined thickness, width and length, <BR/> - heating until temperature is reached before annealing between 90 ° C and 150 ° C, <BR/> - followed by uniform heating from the pre-annealing temperature to a temperature between 5 ° C and 60 ° C below a predetermined target temperature within 2 h - 4 h, target temperature between 450 ° C and 700 ° C, <BR/> - followed by even heating to the target temperature within 0.1 h - 1 h, <BR/> - maintenance of the target temperature for 0.5 h - 2 , 5 h, <BR/> - cooling to temperature after annealing between 200 ° C and 400 ° C within 0.5 h - 2.5 h, <BR/> - followed by cooling from temperature after annealing to room temperature. The invention refers to metal bands, that apart from Fe contains also 0.01% - 0.2% C, 12% - 17% Cr, 4% - 8% Ni,? 3.5% Cu,? 0.5% You,? 1.8% Si and? 2% Mn and the method of producing such bands through the following steps: <BR/> - preparation of metal material for bands with predetermined thickness, width and length, <BR/> - heating up to achieve temperature before annealing between 90 ° C and 150 ° C, <BR/> - there follows uniform heating up from temperature before annealing to the temperature between 5 ° C and 60 ° C below predetermined targeted temperature within 2 h - 4 h, with targeted temperature being between 450 ° C and 700 ° C, <BR/> - there follows uniform heating up to the targeted temperature within 0.1 h - 1 h, <BR/> - maintaining targeted temperature in the time from 0.5 h to 2.5 h, <BR/> - cooling down to the temperature after annealing between 200 ° C and 400 ° C within 0.5 h - 2.5 h, <BR/> - there follows cooling down from temperature after annealing to the room temperature.

Description

The invention relates to metal strips, especially endless strips, and their production process.

Metal strips are used, for example, for band presses or band saws. They include a metal sheet or several metal sheets, which are welded to each other or are welded if necessary. In the event that endless strips are present, which represents the preferred form of use, the strips are cross-welded at the ends, so that they form an endless strip. In the event that wide strips are required, two or more strips are welded, often at their longitudinal edges, so that they form a wide strip.

In a belt press, here double belt presses, the upper and lower endless belts move at the same speed in the work space, with the endless belts running mostly parallel or at a slight angle to each other. A slight angle to each other may be necessary due to the compactness of the raw material for pressing, but also due to the change in volume depending on the temperature.

In the working area, the pressing process takes place, whereby both strips are pressed against each other and this pressure is transferred to the workpiece guided between them during their movement.

The disadvantage of these devices is that conventional tapes have a limited shelf life, especially when heat is applied to the tapes during the pressing process, and they must be replaced after some time.

The task of this invention is to overcome the shortcomings of the state of the art, and to provide metal strips and their production process, with which the user is able to achieve a long service life.

The task is solved using metal strips and the production process according to the requirements.

In the following, % of weight is indicated with the sign %.

Metal strips in accordance with the invention, apart from Fe, which makes up the rest of the mass, also contain unavoidable impurities:

0.01% - 0.2% C,

12% - 18% Cr,

4% - 8% Ni

0% - 3.5% Cu

0% - 0.5% Ti

0% - 1.8% Si and

0% - 2% Mn.

Optionally, the strips contain at least 0.03% C.

Optionally, the strips contain 14% - 17.5% Cr,

Optionally, the strips contain 4% - 7.5% Ni, particularly preferably between 4% and 5% or between 6.5% and 7.5%.

Optionally, the strips contain 0% Cu or between 0.5% and 0.9% Cu or between 3 and 3.5% Cu.

Optionally, the strips contain 0% Ti or between 0.3 and 0.5% Ti,

Optionally, the strips contain 0 % Si or between 0.6 % and 0.8 % Si.

Optionally, the strips contain 0.6% - 1.4% Mn, preferably a maximum of 1% Mn.

Preferably, the hardness [HV 10 ] of the base material (before the heating process) is in the range between 300 and 500, especially below 400. Hardness is indicated here and below according to Vickers.

Preferably, the tensile strength (Rm) of the base material (before the heating process) is between 1000 N/mm² and 1450 N/mm², in particular between 1050 N/mm² and 1200 N/mm².

Preferably, the yield strength of the 0.2% (Rp-0.2) base material (before the heating process) is between 900 N/mm² and 1400 N/mm², in particular between 950 N/mm² and 1100 N/mm².

Preferably, the fatigue limit of the material due to bending of the base material (before the heating process) is between 400 N/mm² and 600 N/mm², especially between 450 N/mm² and 550 N/mm².

Preferably, the tensile strength (Rm) of the cross-welded base material (before the heating process) is between 800 N/mm² and 1200 N/mm², especially between 900 N/mm² and 1100 N/mm².

The manufacturing process according to the invention of such metal strips includes the following steps:

- preparing the metal material for the strips according to the previous procedures with predetermined thickness, width and length,

- optional: joining of at least two metal strip materials at the longitudinal edges into a wider strip material by means of welding (longitudinal welding),

- heating until reaching a temperature before annealing between 90°C and 150°C,

- it is followed by uniform heating from the temperature before annealing to a temperature between 5°C and 60°C, especially to a temperature between 20°C and 40°C, below the predetermined target temperature in a time between 2 h - 4 h, whereby the target temperature is between 450°C and 700°C,

- followed by uniform heating to the target temperature within 0.1 h - 1 h,

- maintaining the target temperature for 0.5 h - 2.5 h ("maintenance temperature"),

- cooling to a temperature after annealing between 200°C and 400°C within a time between 0.5 h - 2.5 h,

- followed by cooling from the temperature after annealing to room temperature,

- optional: joining the ends of the heat-treated material into an endless strip by means of welding (transverse welding).

It is preferred that the temperature before annealing is between 100°C and 140°C, especially between 110°C and 130°C, with a temperature of 120°C (+/- 2°C) being particularly preferred. The time in which this must take place does not have to be specifically determined, but it has been shown to be effective, if the heating time is between 0.2 h and 1 h.

Preferably, the heating is carried out from the pre-annealing temperature to a temperature below the predetermined target temperature within 2.5 h - 4 h, especially within 3 h (+/- 10 min).

It is preferable that the heating to the target temperature is carried out within a time of 0.5 h (+/- 5 min).

It is preferable that the maintenance of the target temperature is carried out within a time between 1 h - 2 h, especially 1.5 h (+/- 10 min).

It is preferable that the temperature after annealing is between 250°C and 350°C, especially at 300°C (+/- 10°C).

It is preferable that the cooling to the temperature after annealing is carried out in a time between 1 h - 2 h, especially in 1.5 h (+/- 10 min).

The target temperature depends on the strip material used, and is preferably between 450°C and 600°C. In a preferred embodiment, the target temperature is located on the downward curve of the heat treatment, in the region in which the function of the strength of the heat-treated strip material depending on the maintenance temperature has a negative slope.

The heat treatment curve shows the strength function of the heat treated tape material (Y axis) as a function of the maintenance temperature (X axis). This curve rises at a low maintenance temperature with an increase in temperature, reaches a maximum and falls with a further increase in temperature (negative slope).

It is preferable that the maintenance temperature is chosen so that it is higher than the maximum temperature of the curve, that is, it is chosen so that the function there has a negative derivative related to the temperature.

Here, the advantage is that the finished tape becomes softer and more flexible if it experiences high temperatures in use. The probability of failure in the form of breakage is thereby minimized.

Preferably, the hardness [HV 10] of the heat-treated strip is between 400 and 600, especially below 500.

Preferably, the hardness [HV 10] of the heat-treated strip versus the base material increases between 100 and 200.

Preferably, the tensile strength of the heat-treated strip is between 1300 N/mm² and 1700 N/mm², in particular between 1450 N/mm² and 1600 N/mm².

Preferably, the tensile strength of the heat-treated strip against the base material increases between 350 N/mm² and 500 N/mm², in particular between 380 N/mm² and 450 N/mm².

Preferably, the 0.2% yield strength of the heat-treated strip is between 1300 N/mm² and 1700 N/mm², in particular between 1400 N/mm² and 1550 N/mm².

Preferably, the yield strength of the 0.2% heat-treated strip against the base material increases between 350 N/mm² and 500 N/mm², in particular between 380 N/mm² and 430 N/mm².

Preferably, the fatigue limit of the material due to bending of the heat-treated strip is between 600 N/mm² and 800 N/mm², in particular between 630 N/mm² and 720 N/mm².

Preferably, the fatigue limit of the material due to bending of the heat-treated strip against the base material increases between 100 N/mm² and 300 N/mm², in particular between 180 N/mm² and 220 N/mm².

Preferably, the tensile strength of the transversely welded joint of the heat-treated strip is between 1000 N/mm² and 1300 N/mm², in particular between 1180 N/mm² and 1250 N/mm².

Preferably, the tensile strength of the transversely welded joint of the heat-treated strip compared to the transversely welded joint in the base material increases between 20 N/mm² and 150 N/mm², in particular between 30 N/mm² and 110 N/mm².

Preferably, the tensile strength of the longitudinally welded joint of the heat-treated strip is between 1200 N/mm² and 1700 N/mm², in particular between 1310 N/mm² and 1550 N/mm².

Hardness, tensile strength, yield strength and material fatigue limit due to bending of the base material in the presence of heat-treated material can be easily determined by determining the chemical composition based on professional literature or by subsequent production of the base material without heat treatment.

The heat treatment of the strips is preferably carried out in a furnace. During the heat treatment, the tape is preferably wound into a coil. During the winding of the reel, metal foil, for example copper foil, can be additionally wound together with the material for the tapes. The advantage here is that the layers of tape material rolls do not scratch each other.

In accordance with the preferred embodiment, the strips are between 20 m and 190 m long, preferably between 40 m and 170 m. In the case of endless strips, the cycle length over the entire strip is understood. This represents a favorable length of wood belt and conveyor belt.

In the event that finished strips in the form of endless strips are required, heat treatment follows in the preferred embodiment before welding into an endless strip.

In the event that two or more strips are longitudinally welded into a wide strip, in a preferred embodiment heat treatment follows preferably after welding. According to a further preferred embodiment, welding follows heat treatment.

Examples of preferred embodiments according to the invention are presented below.

Example 1

The metal material for the strips contains a maximum of 0.09% C, 15% Cr, 7% Ni, 0.7% Cu, 0.4% Ti and the rest Fe. Its tensile strength is 1150 N/mm², and its hardness [HV 10] 360.

After heat treatment according to the procedure according to the invention at a maintenance temperature of 540°C - 570°C, its tensile strength is 1550 N/mm², and its hardness [HV 10] 480.

Example 2

The metal material for the strips contains 0.03% C, 14.5% Cr, 4.5% Ni, 3.3% Cu and the rest Fe. Its tensile strength is 1050 N/mm², and its hardness [HV 10] 330.

After heat treatment according to the procedure according to the invention at a maintenance temperature of 470°C - 520°C, its tensile strength is 1450 N/mm², and its hardness [HV 10] 460.

In the examples, it can be clearly seen that heat treatment increases the tensile strength and hardness of the material. This increase is due to the separation of the precipitation element from the thermodynamically dissolved state. Separated elements form phases that prevent shearing and thus cause an increase in hardness and strength.

In examples 1 and 2, during heat treatment, as a rule, one element is separated from the crystalline compound without leaving the strip material (separated hardened element). The corresponding substance is therefore still chemically present, but is no longer part of the underlying microstructure. The materials in examples 1 and 2 are both martensitic materials. In example 1, Ti is the isolated hardened element of the alloy, in example 2 Cu is the isolated hardened element of the alloy.

The examples of implementations describe possible implementation variants, where it should be noted here that the invention is not limited to the specifically shown implementation variants, but even more so, various combinations of individual implementation variants are possible with each other, and these options of variants are based on the science for the technical handling of the subject invention of the person from of that technical field.

Numerous performance variants are also possible, which are possible through the combination of individual details of the shown and described performance variants, included in the scope.

Independent innovative solutions on which the invention is based can be found in the description.

All details relating to the range of values in the description shown should be understood to include any and all parts of the range, for example the specification 0% to 1% should be understood to include a number of ranges, starting with the lower limit of 0% (not included ) and upper limits of 1%, i.e. numerous ranges start with a lower limit of 0% or more and end at an upper limit of 1%, or less eg 0% to 0.7% or 0.1% to 1%, or 0.5% to 0.9 %.

First of all, individual embodiments can form the subject of independent solutions in accordance with the invention.

Claims (5)

1. Metal strip produced by heat treatment in the following steps: - bringing in a metal strip of predetermined thickness, width and length, - heating until reaching a temperature before annealing between 90°C and 150°C, - followed by uniform heating from the pre-annealing temperature to a temperature between 5°C and 60°C below the predetermined target temperature within a time between 2 h - 4 h, where the target temperature is between 450°C and 700°C, - followed by uniform heating to the target temperature within 0.1 h - 1 h, - maintaining the target temperature for 0.5 h - 2.5 h, - cooling to a temperature after annealing between 200°C and 400°C within a time of 0.5 h - 2.5 h, - followed by cooling from the temperature after annealing to room temperature, characterized by the fact that, in addition to Fe, which forms the rest of the mass, along with unavoidable admixtures, it additionally contains, expressed in mass fractions: 0.01% - 0.2% C, 12% - 18% Cr, 4% - 8% Ni, ≤ 3.5% Cu, ≤ 0.5% Ti, ≤ 1.8% Si and ≤ 2% Mn; and has a hardness [HV 10] between 400 and 600 and/or a tensile strength between 1300 N/mm2 and 1700 N/mm2 and/or a yield strength of 0.2% between 1300 N/mm2 and 1700 N/mm2 and/or a fatigue strength material due to bending between 600 N/mm2 and 800 N/mm2. 2. Metal strip according to claim 1, characterized in that the strip is between 20 m and 190 m long, preferably between 40 and 170 m. 3. Metal strip according to one of the preceding claims, characterized in that the base material before the heating process has a hardness [HV 10] between 300 and 500 and/or a tensile strength (Rm) between 1000 N/mm² and 1450 N/mm² and/or tensile strength 0.2% (Rp-0.2) between 900 N/mm² and 1400 N/mm² and/or fatigue strength of the material due to bending between 400 N/mm² and 600 N/mm² and/or tensile strength (Rm) transversely of the welded joint between 800 N/mm² and 1200 N/mm². 4. Metal strip according to one of the previous claims, characterized by the fact that in the heat-treated endless strip, the hardness [HV 10] increases between 100 and 200 and/or the tensile strength between 350 N/mm² and 500 N/ mm² and/or yield strength 0.2% between 350 N/mm² and 500 N/mm² and/or material bending fatigue strength between 100 N/mm² and 300 N/mm² and/or transverse weld tensile strength between 20 N/ mm² and 150 N/mm². 5. Metal strip according to one of the previous claims, characterized in that it contains a transverse weld and/or a longitudinal weld, wherein the tensile strength of the transverse welded joint of the heat-treated strip is between 1000 N/mm2 and 1300 N/mm2, especially between 1180 N/ mm2 and 1250 N/mm2 and/or the tensile strength of the longitudinally welded joint of the heat-treated strip between 1200 N/mm2 and 1700 N/mm2.