CZ307337B6 - A method of manufacturing wooden beams with hot moulded steel reinforcement - Google Patents

Abstract

The method of manufacturing wooden beams comprises the following steps:- heating the steel reinforcement (2) to the temperature of the austenite of the material from which it is made;- heating the wooden honeycomb (3) to the temperature lying between the Ms and Mf of the material from which the reinforcement (2) is made;- applying a heat-resistant adhesive to the surface of at least one reinforcement (2) piece and/or the wooden honeycomb (3);- moulding of the reinforcement (2) onto the surface of the wooden honeycomb (3) in a moulding tool defining the future shape of the wooden beam (1);- maintaining the wooden beam (1) in the moulding tool for at least the time of alignment of the reinforcement (2) and the honeycomb (3) temperatures and their mutual cooling, including the process of stabilizing the residual austenite and tempering the martensite in the reinforcement steel (2) and curing the adhesive.The beam may contain multiple alternating layers of the reinforcement (2), the adhesive and the wooden honeycombs (3). The reinforcement (2) may be provided with a protruding shape lock (4), which is moulded into the wooden honeycomb (3). The honeycomb (3) may be provided, on the surface, with a reduced area (6) into which at least one reinforcement (2) piece is placed.

Description

Technical field

The present invention relates to a method for the production of wood sandwich beams reinforced with high-strength steel reinforcement.

BACKGROUND OF THE INVENTION

Wooden sandwich beams, preferably usable for construction, are made by gluing of stacked wooden honeycombs in presses. The individual wooden honeycombs are provided with a layer of glue on their contact surfaces and are inserted into the press jig. The shape of the used fixture is determined by the shape of the beam. After the adhesive has cured, the finished beam can be removed from the fixture, the shape of the beam defined by the fixture is already fixed.

The deflection of the finished beam, which affects the bearing capacity, is given by the E-modulus, the modulus of resistance of the cross-section and the structure of the beam. The desirable increase in the modulus of resistance of the cross-section in bending results in an undesirable increase in cross-section, in particular its height, in the case of a standard beam design. This results in an increase in the weight of the beam and the consumption of material which, due to its natural origin, is only available in limited quantities in the required quality.

A well known technology for quenching steel parts consists in heating the steel to its austenitization temperature, at which crystals are transformed from ferrite to austenite crystals, followed by gradual and controlled cooling. When cooling from the austenitization temperature below the temperature Ms of the steel (transformation start temperature), the austenite is transformed into the turbidity of martensite, ev. bainitu. The lower limit of this temperature zone of the martensitic conversion of steel is given by the temperature Mf of the steel (temperature of the end of conversion). If there is a rapid decrease from austenite temperature to a temperature between Ms and Mf of a given steel, only austenite is partially transformed. The residual austenite content remains in the controlled martensite structure in a controlled manner. Subsequent slow total cooling from the temperature above the Mf of the steel stabilizes the residual austenite in the steel and tempers the martensite. This diffuses the carbon from the supersaturated martensite into the residual austenite, which is thereby stabilized and retained in the microstructure after gradual cooling to ambient temperature. Incomplete turbidity and stabilization of the residual austenite will result in high strength and very good ductility of the treated steel member.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention is directed to a method for producing hot-formed wooden beams. The method comprises the steps of:

- heating at least one steel reinforcement to austenite temperature of the material from which it is made;

- heating at least one wooden honeycomb to a temperature lying between Ms and Mf of the material from which the reinforcement is made;

- applying a heat-resistant adhesive to at least a portion of the surface of the at least one reinforcement and / or to at least a portion of the surface of the at least one wood honeycomb;

- pressing the at least one heated reinforcement into the surface of the at least one heated wooden honeycomb in a die defining the future shape of the wooden beam;

- retaining the timber beam in the die for at least the time of equilibrating at least one reinforcement and at least one wood honeycomb and cooling them together, which includes a process of stabilizing the residual austenite and tempering the martensite in the reinforcement steel and curing

Adhesives. Depending on the chemical composition of the steel, the cooling rate must meet the condition that most of the austenitic matrix will be transformed into martensite.

In one embodiment, depending on the required load-bearing capacity of the wooden beam to be manufactured, a plurality of alternating layers of reinforcement, adhesive and wood honeycombs are inserted into the die prior to compression. It is particularly suitable if one reinforcement is glued and pressed between two wooden honeycombs. This is also advantageous with regard to the protection of the raw steel sheet reinforcement from the air. However, the production of a beam consisting of a plurality of such stacks may also be envisaged, eg wood honeycomb + reinforcement + wood honeycomb + reinforcement + wood honeycomb.

In another possible embodiment, the at least one wood honeycomb is moistened prior to pressing. The wetting can be carried out, for example, with steam. The damp wood honeycomb material can facilitate bending in the die. Increased humidity can also prevent unwanted opalization of the wood honeycomb surface with heated reinforcement.

In order to ensure a higher strength, it is suitable if the at least one reinforcement is provided with at least one protruding form lock which is pressed into the at least one wooden honeycomb when the timber beam is pressed. It is particularly advantageous to manufacture a system of punched and bent teeth at the edge of the reinforcement sheet, which are pressed into the wood honeycomb mass by the pressure in the die.

If a very high strength of the manufactured beam is required, the individual layers of the wooden beam can be tightened together by at least one bolt. By a bolt is meant here, for example, a screw provided with a nut extending through a through hole across all layers of the beam. Another possible type of bolt may be a U-shaped element embracing from outside the three walls of the beam to which a bolt plate situated on the fourth wall of the beam is screwed. Bolt reinforcement increases the possible operational bending stress of the finished beam, prevents the layers from breaking and the beam from tearing.

Depending on the thickness of the reinforcement, the hardness of the wood honeycomb and the pressing pressure, it may be advantageous if at least one of the at least two wood honeycombs is provided with at least one lowered area on its surface adjacent to the adjacent wood honeycomb. At least one reinforcement is placed in this lowered area. As a result, the surrounding surfaces of the adjacent walls of the wooden honeycombs can be in direct contact and be sufficiently glued together.

In order to provide a greater contact area of adjacent wooden honeycomb walls, it is advantageous if at least one reinforcement is provided with at least one through hole in the area of its body. As a result, the surfaces of the adjoining walls of the wooden honeycombs can be glued together not only around the reinforcement, respectively. lowered areas, but also in the reinforcement area.

For some applications, it may be advantageous if at least one reinforcement is provided at the periphery of its body with a shaped edge. This ensures greater contact area of the adjacent walls of wooden honeycombs. In addition, it is a kind of shaped lock, it helps to prevent the reinforcement from moving along the wall of the wooden honeycomb.

Clarification of drawings

An exemplary embodiment of the proposed solution is described with reference to the drawings, in which Fig. 1 is a schematic axonometric view of a possible form of reinforcement;

Fig. 2 is a schematic axonometric view of a wooden honeycomb provided with a lowered area;

FIG. 3 shows a beam comprising two wooden honeycombs and two bolts passing through the beam.

-2GB 307337 B6

DETAILED DESCRIPTION OF THE INVENTION

The wooden honeycombs 3 are preheated to a temperature of 200 ° C and provided with an adhesive. Steel reinforcement 2 with composition see tab. 1 is heated to a temperature of 900 ° C and inserted between two wooden honeycombs 3. Thereafter, the molding is carried out in such a way that the reinforcement 2 contacts the wooden honeycombs 3. The locks 4 of the reinforcement 2 penetrate into the wooden honeycombs 3 and according to the shape of the jig. As a result, the reinforcement 2 is mechanically anchored. In contact with the wood honeycombs 3, the temperature of the reinforcement 2 rapidly decreases to approximately the temperature of the wood honeycombs 3, i.e. between 180 and 250 ° C, resulting in incomplete turbidity of the reinforcement material 2. After compression, the austenite is transformed to turbidity. martensite structure, ev. bainitu. Since the wooden honeycombs 3 are preheated above the temperature Mf of the steel, there is no complete transformation. The proportion of residual austenite remains in the structure of the transformed martensite. Thereafter, the temperatures of the reinforcement 2 are equal to the temperature of the wood honeycombs 3, followed by co-cooling to stabilize the residual austenite in the steel, temper the martensite and cure the adhesive joining the wood honeycombs. the carbon diffuses from the supersaturated martensite to the residual austenite, which is thereby stabilized and is retained in the microstructure after gradual cooling to ambient temperature. The shrinkage of the steel is partly used for mechanically anchoring the shape locks 4 to the wooden honeycombs 3 and its remaining component is compensated by the transformation plasticity. Incomplete turbidity and stabilization of residual austenite will result in high strength and very good ductility. Then the finished beam 1 is removed from the fixture.

C Si Mn Cr 0.4 2 0.8 1.5

Tab. 1: Chemical composition of the material in% wt. (the remainder to 100 wt.% is Fe)

Industrial applicability

The invention is widely applicable in the field of wood glued beam production, especially for the construction industry. It relates to a method for producing a timber beam with steel reinforcement which, during the beam manufacturing process, obtains a multiphase structure of high strength and increased ductility due to a suitable cooling rate from the austenite temperature region.

Claims (8)

PATENT CLAIMS A method for producing hot-pressed timber beams, comprising the steps of: - at least one steel reinforcement (2) is heated to the austenitization temperature of the material from which it is made; - at least one wood honeycomb (3) heats to a temperature lying between Ms and Mf of the material from which the reinforcement (2) is made; - apply a heat-resistant adhesive on at least a portion of the surface of the at least one reinforcement (2) and / or at least a portion of the surface of the at least one wood honeycomb (3); - presses the at least one heated reinforcement (2) into the surface of the at least one heated wooden honeycomb (3) in a die defining the future shape of the wooden beam (1); -3 CZ 307337 B6 - keeps the wood beam (1) in the press jig for at least the time of equilibrating at least one reinforcement (2) and at least one wood honeycomb (3) and co-cooling them, comprising a process of stabilizing residual austenite and tempering martensite in steel reinforcement (2) and curing adhesives. Method for the production of hot-pressed wooden beams according to claim 1, characterized in that a plurality of alternating reinforcements (2), adhesive and wood honeycombs (3) are inserted into the die prior to pressing the wooden beam (1). Method for producing hot-pressed wooden beams according to one of the preceding claims, characterized in that at least one wooden honeycomb (3) is moistened before pressing. Method for the production of hot-pressed wooden beams according to one of the preceding claims, characterized in that at least one reinforcement (2) is provided with at least one protruding shaped lock (4) which, when pressing the wooden beam (1) press into at least one wooden honeycomb (3). Method for producing hot-pressed wooden beams according to one of the preceding claims, characterized in that the individual layers of the wooden beam (1) are pulled together by at least one bolt (5). Method for the production of hot-pressed wooden beams according to one of the preceding claims, characterized in that at least one of the at least two joined wooden honeycombs (3) is provided on its surface adjacent to the adjacent wooden honeycomb (3). at least one lowered area (6) in which at least one reinforcement (2) is deposited. Method for producing hot-pressed wooden beams according to one of the preceding claims, characterized in that at least one reinforcement (2) is provided with at least one through hole (7) in the area of its body. Method for producing hot-pressed wooden beams according to one of the preceding claims, characterized in that at least one reinforcement (2) is provided with a shaped edge (8) at the periphery of its body.