The present invention relates to the technical field of material processing and provides a method for making a metal material composite, including: contacting a first surface of a first plate with a second surface of a second plate; placing the first plate and the second plate in a recess in a circumferential direction of a first roller such that a third surface of the second plate contacts a bottom wall of the recess in a circumferential, the third surface being opposite the second surface, the first plate having a greater hardness than the second plate; and controlling a first roller and a second roller to rotate, thereby rolling to combine the first plate and the second plate into a composite plate, where a fourth surface of the first plate contacts a surface of the second roller and the fourth surface is opposite the first surface during the rolling. According to the method for making a metal material composite in the present invention, flashings and burr on the side edges of a composite plate are avoided by placing the first plate and the second plate in a recess for machining.

The present invention provides a composite plate, a composite plate roughening device, and a method for manufacturing a composite plate, and relates to the technical field of metal plate materials. The composite plate includes a first plate and a second plate, wherein a first side surface of the first plate is provided with striations, the first side surface of the second plate and the first side surface of the first plate are rolled to connect, and the striations of which adjacent ones have a pitch of 0.005 mm to 0.03 mm account for more than 90% of all the striations. For the composite plate described in the embodiments of the present invention, the first side surface of the first plate is roughened such that the first side surface of the first plate and/or the first side surface of the second plate is configured with striations, which increases an area of the first plate and the second plate subjected to rolling, whereby the composite plate produced by combining the first plate and the second plate has a higher bonding strength and thus a stronger bonding.

The present invention provides a cell phone frame and a method for manufacturing the same, and relates to the technical field of cell phone accessories. The cell phone frame includes a composite plate, the composite plate encloses a accommodation space for accommodating the cell phone, the composite plate includes a first plate and a second plate, a first side surface of the first plate is provided with striations, the first side surface of the second plate and the first side surface of the first plate are rolled to connect, and the striations of which adjacent ones have a pitch of 0.005 mm to 0.03 mm account for more than 90% of all the striations. According to the cell phone frame provided in the embodiment of the present invention, the first side surface of the first plate is roughened to form striations, which increases the area of the first plate and the second plate subjected to rolling, so that a composite plate produced by combining the first plate and the second plate has a higher bonding strength, thereby ensuring that the cell phone frame is firmer.

The invention relates to a method for producing a steel composite in which at least two steel sheets that consist of different steel grades are placed against each other, hot rolled together, and then possibly cold rolled and in which after the rolling, the composite material, which is thus produced from at least two layers with different steel compositions, is diffusion annealed, wherein the annealing temperature is set so as to select the chemical potential of the steel materials to correspond to the following equation:

.sub.C, material 1>.sub.C, material 2,

where material 1 has a lower carbon content than material 2 so that an uphill diffusion of carbon takes place between material 1 and material 2.

The invention relates to a method for producing a steel composite in which at least two steel sheets that consist of different steel grades are placed against each other, hot rolled together, and then possibly cold rolled and in which after the rolling, the composite material, which is thus produced from at least two layers with different steel compositions, is diffusion annealed, wherein the annealing temperature is set so as to select the chemical potential of the steel materials to correspond to the following equation:

.sub.C, material 1>.sub.C, material 2,

where material 1 has a lower carbon content than material 2 so that an uphill diffusion of carbon takes place between material 1 and material 2.

A system and method for producing a seamless pipe from a hollow billet with a smaller diameter than the seamless pipe, uses a pressure container configured to house the hollow billet. The hollow billet is surrounded by a fluid. A movable punch arranged to fit inside the hollow billet, wherein a hydraulic pressure is transferred from the fluid to the movable punch and to the hollow billet simultaneously, along at least a partial length of the hollow billet. A die opening is arranged serial to the pressure container, wherein the die opening is configured to house a fixed mandrel, the fixed mandrel having a diameter larger than an inner diameter of the hollow billet, so that a gap is formed between the die opening and the fixed mandrel, and the hydraulic pressure of the fluid is generated by an input force from an input punch to move the hollow billet towards the die opening and force the hollow billet material into the gap between the die opening and the fixed mandrel.

A system and method for producing a seamless pipe from a hollow billet with a smaller diameter than the seamless pipe, uses a pressure container configured to house the hollow billet. The hollow billet is surrounded by a fluid. A movable punch arranged to fit inside the hollow billet, wherein a hydraulic pressure is transferred from the fluid to the movable punch and to the hollow billet simultaneously, along at least a partial length of the hollow billet. A die opening is arranged serial to the pressure container, wherein the die opening is configured to house a fixed mandrel, the fixed mandrel having a diameter larger than an inner diameter of the hollow billet, so that a gap is formed between the die opening and the fixed mandrel, and the hydraulic pressure of the fluid is generated by an input force from an input punch to move the hollow billet towards the die opening and force the hollow billet material into the gap between the die opening and the fixed mandrel.

There are provided: a seamless steel pipe formed from a cylindrical steel material billet through a hot isostatic extrusion step, wherein a depth of a contiguous flaw formed on an inner periphery surface and an outer periphery surface of the steel pipe is 50 m or less; a hollow spring obtained by forming a hollow body in a shape of a coil or a bar or a bar with curved part from the seamless steel pipe made of spring steel and applying a surface treatment to the hollow body so that the hollow body has compressive residual stress; and a method for producing seamless steel pipe including: a billet molding step; a first heating step; a hot isostatic extrusion step; a second heating step; an extension step; a third heating step; and a pickling step.

A cell phone frame includes a composite plate, the composite plate encloses a accommodation space for accommodating the cell phone, the composite plate includes a first plate and a second plate, a first side surface of the first plate is provided with striations, the first side surface of the second plate and the first side surface of the first plate are rolled to connect, and the striations of which adjacent ones have a pitch of 0.005 mm to 0.03 mm account for more than 90% of all the striations. The first side surface of the first plate is roughened to form striations, which increases the area of the first plate and the second plate subjected to rolling, so that a composite plate produced by combining the first plate and the second plate has a higher bonding strength, thereby ensuring that the cell phone frame is firmer.

A cell phone frame includes a composite plate, the composite plate encloses a accommodation space for accommodating the cell phone, the composite plate includes a first plate and a second plate, a first side surface of the first plate is provided with striations, the first side surface of the second plate and the first side surface of the first plate are rolled to connect, and the striations of which adjacent ones have a pitch of 0.005 mm to 0.03 mm account for more than 90% of all the striations. The first side surface of the first plate is roughened to form striations, which increases the area of the first plate and the second plate subjected to rolling, so that a composite plate produced by combining the first plate and the second plate has a higher bonding strength, thereby ensuring that the cell phone frame is firmer.