JP5212894B2 - Continuous casting and rolling apparatus and metal member manufacturing method - Google Patents

Description

  The present invention relates to a light metal or light metal alloy continuous casting and rolling apparatus and a method for producing a metal member using the continuous casting and rolling apparatus, and particularly to improvement of the metal structure of the metal member.

  Conventionally, a DC (Direct Chill) method is well known as a method for manufacturing an aluminum plate. As shown in FIG. 14, this starts from melting the aluminum raw material, and obtains an aluminum plate through the steps of slab casting, homogenization treatment, face cutting, heating, hot rolling, and cold rolling. Is. On the other hand, a continuous casting and rolling (CC) method in which an aluminum plate material is directly produced from a molten aluminum material is also well known.

  One of the typical CC methods is a twin roll horizontal continuous casting and rolling method. As shown in FIG. 15, a molten aluminum is poured between a pair of upper and lower rollers with a ceramic nozzle, and an aluminum plate is extruded in the rolling direction, which is relatively thin compared to other CC methods. It has the feature that a plate material can be manufactured.

  In addition, the CC method includes a belt type that continuously casts and rolls a plate material, a connection block type, or a wheel / belt type that continuously casts and rolls a bar-shaped billet. These CC methods are compared with the DC method. There are few processes, and there are various advantages such as cost reduction, reduction of input energy, and improvement of material properties by rapid solidification.

  Patent Document 1 proposes a twin-roll horizontal continuous casting and rolling apparatus for an aluminum alloy (hereinafter referred to as Al alloy) containing no Cr.

JP 2006-130545 A

  On the other hand, in the automobile field, with the demand for weight reduction of a vehicle body, an aluminum alloy (hereinafter referred to as an Al alloy) having a specific gravity of about 1/3 of that of a steel plate has been attracting attention. Al alloys have been used for casting members of engines and the like, but recently, molding by the DC method using Al alloys has been carried out as outer plates for automobile bodies such as roofs, trunk lids and doors.

  However, in the CC method, when a vehicle body part using an Al alloy is manufactured, if the obtained Al alloy member is subjected to plastic processing such as press working without being faced, bending portions and corners are produced. Remarkable cracks, wrinkles, and deformation due to shape freezing occur in the parts. Al alloys are generally inferior in formability due to reasons such as low material elongation and Young's modulus compared to steel sheets, but the tendency becomes even more pronounced when applied to the CC method.

The transition elements Cr and Mn in the Al alloy have a function of refining the crystal grain size during the solution treatment. However, when the CC method is applied, processing strain occurs on the surface of the Al alloy member due to the rolling load during the continuous casting and rolling process, and the surface of the obtained Al alloy member has coarse crystal grains due to Cr. It has been found that crystallization has occurred.
Although the CC method has the various advantages described above, it has a specific problem of coarsening the surface crystal grains. If this problem is not solved, the use and development of various members is limited.

In general, it is known that refinement of the metal structure of CC material is improved by refinement of the cast structure by increasing the cooling rate and suppressing the coarsening of recrystallized grains by increasing the rolling load during casting. ing.
However, for the purpose of increasing the cooling rate, it is conceivable to change from a conventional tool steel roll to a copper roll with high thermal conductivity, but because the copper strength is insufficient, a high rolling load is applied during casting. It is difficult to hang. Further, the range of increase in the cooling rate is limited in the conventional steel roll.
Patent Document 1 does not mention coexistence of increasing the cooling rate and increasing the rolling load during casting.

  The object of the present invention is to achieve both the refinement of the cast structure by increasing the cooling rate and the suppression of the coarsening of the recrystallized grains by increasing the rolling load during casting in the continuous casting of light metal or light metal alloy. It is providing the manufacturing method of the continuous casting rolling apparatus and metal member which can achieve refinement | miniaturization of metal.

The continuous casting and rolling apparatus according to claim 1 pours a molten metal of light metal or light metal alloy between a pair of upper and lower rollers, and pushes the molten metal as a plate-like continuous cast and rolled material in the rolling direction while applying a rolling load by the rollers. in the continuous casting and rolling apparatus issues, the upper stream side roll arranged upstream of the rolling direction, and the lower stream side roll arranged downstream of the this upstream roller, while being arranged below the molten metal A single lower roll that is positioned opposite to the downstream roll and applies a reduction load to the molten metal together with the downstream roll, and the upstream roll is made of a material having higher thermal conductivity than the downstream roll. The downstream roll and the lower roll are formed of a material having higher strength than the upstream roll .

The continuous casting and rolling apparatus according to claim 2 is characterized in that, in the invention of claim 1 , the rotation center of the downstream roll is located on a substantially vertical plane passing through the rotation center of the lower roll.

Method for producing a metal member according to claim 3 is a method for producing a metal member by using a continuous casting and rolling apparatus according to claim 1, a first step of continuous casting and rolling a molten light metal or light metal alloy, this A second step of performing a heat treatment for heating the continuous cast rolled material to a recrystallization temperature or higher during continuous casting rolling or after the continuous cast rolling , and the second step is a step of recrystallizing the continuous cast rolled material. After the above heating, it is a step of quenching and solution treatment, a third step of plastic processing the continuous cast rolled material after the solution treatment, a fourth step of artificial aging treatment after the plastic processing, It is characterized by having.

According to the first aspect of the present invention, a molten metal of light metal or light metal alloy is poured between a pair of upper and lower rollers, and the molten metal is extruded as a plate-like continuous cast rolled material in the rolling direction while applying a rolling load by the rollers. in the continuous casting and rolling apparatus, the downstream roller and the upper stream side roll arranged upstream of the rolling direction, and the lower stream side roll arranged downstream of the this upstream roller, while being arranged below the molten metal And a single lower roll that applies a rolling load to the molten metal together with the downstream roll, and the upstream roll is formed of a material having a higher thermal conductivity than the downstream roll and the downstream roll Since the roll and the lower roll are formed of a material having higher strength than the upstream roll, it is possible to achieve both a higher cooling rate and an increased reduction load during casting.

That is, by providing each roll with the contradictory functions, the downstream structure roll is made of a material having a higher strength than the upstream roll by refining the cast structure with the upstream roll made of a material having high thermal conductivity. In addition, due to the high pressure under load of the lower roll , processing strain can be introduced into the material, and the recrystallized structure can be further refined by using heating above the recrystallization temperature.

In addition, an increase in the cooling rate can improve productivity, and an increase in the rolling load at the time of casting can reduce the thickness of the member and improve the accuracy of the plate thickness. it can.
The lower roll is provided with a single lower roll that is disposed on the lower side of the molten metal and is opposed to the downstream roll and applies a reduction load to the molten metal together with the downstream roll. Since it is formed of a material having higher strength than the side roll, the number of rolls can be reduced, the structure can be simplified, and roll drive control can be facilitated.

According to the invention of claim 2 , since the rotation center of the downstream roll is located on a substantially vertical plane passing through the rotation center of the lower roll, it is easily and stably reduced with respect to the continuously cast rolled material. A load can be applied.

According to invention of Claim 3 , in the method of manufacturing a metal member using the continuous casting rolling apparatus of Claim 1 , the 1st process of carrying out continuous casting rolling of the molten metal of a light metal or a light metal alloy, and this continuous casting rolling In this case, or after continuous casting and rolling, there is a second step of performing a heat treatment for heating the continuously cast and rolled material to the recrystallization temperature or higher, so that improvement of mechanical properties by recrystallization is expected. In addition, the second step is a step in which the continuous cast rolled material is heated to the recrystallization temperature or higher, and then subjected to a solution treatment by quenching, and the third step in which the continuous cast rolled material after the solution treatment is plastically processed and And a fourth step of artificial aging treatment after plastic working, so that it is possible to achieve both plastic workability and physical properties of the final product while solving the problem of thermal deformation of continuously cast rolled material due to solution treatment. Become.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1A is a side view of a vehicle body part 1 formed of a 6000 series Al alloy that is a plastic working member according to the present embodiment, and FIG. The vehicle body component 50 is a chassis component that extends and is attached to the vehicle body in the longitudinal direction under the floor in order to increase the rigidity of the lower portion of the vehicle body. The upper and lower edges of the vehicle body part 50 are bent at substantially right angles in the horizontal direction in opposite directions. The plate thickness is 3 mm or less.

The vehicle body part 1 is manufactured through the steps shown in FIG. First, the aluminum plate is continuously cast and rolled (CC). In this CC process, an Al alloy is melted by a twin-roll horizontal continuous casting and rolling method to produce an Al plate having a thickness of 3 mm or less.
Then, as shown in FIG. 2, a final molded product is formed through press molding and artificial aging treatment as homogenization treatment, solution treatment, and plastic working.

As shown in Table 1, the Al alloy used in the vehicle body part 50 has Si, Fe, Cu, Mn, Mg, Zn, Cr, and Ti as alloy elements, and these alloy elements are JIS standard 6061. The same composition range as that of the system alloy is set.

As shown in FIG. 3, the CC device includes a lower roll 1, a first roll 2 disposed on the upper side of the lower roll 1, and a second roll 3 disposed immediately downstream of the first roll 2. The first roll 2 and the second roll 3 face each other via the lower roll 1 and the nips 4 and 5. The lower roll 1 and the second roll 3 are made of tool steel, and the first roll 2 is made of copper having a high thermal conductivity.
The molten Al alloy M moves from the crucible 6 through the nozzle 7 to the rod 8 installed on the lower roll 1, and then a rolling load is applied by the first roll 2 and the second roll 3, and the guide roller 9 To the next process.

Production conditions such as casting speed, setback, roll gap, molten metal temperature and nozzle opening height are as shown in Tables 2 and 3.
The first roll 2 and the second roll 3 are configured to be able to advance and retract with respect to the lower roll 1, and in order to roll the Al alloy M passing through the first and second nips 4 and 5 by this advance / retreat operation. The rolling load is controlled.
The rolling load at the first nip 4 by the first roll 2 is set to 0.1 to 0.5 kN / mm and the solidification rate is 2000 ° C./sec or more.

  The rolling load at the second nip 5 by the second roll 3 is set to 1 to 15 kN / mm and the solidification rate is 1000 ° C./sec or less.

  At the first nip 4 by the first roll 2, the molten Al alloy M is rapidly solidified and the cast structure is refined. Further, the processing roll is introduced into the solidified Al alloy M by rolling at the second nip 5 by the second roll 3, and the recrystallized grains are refined during the heat treatment process described later. The rolling can be performed hot or cold depending on the initial molten metal temperature, the casting conditions at the first nip 4 and the apparatus structure, and the thickness of the sheet can be adjusted. In addition, as a material of the 1st roll 2, what has a high thermal conductivity of copper alloys, such as brass, aluminum, and Al alloy, is applicable. Moreover, as a material of the 2nd roll 3, what is necessary is just a high intensity | strength, and cast iron is applicable.

  As shown in FIG. 4, a heat treatment as a homogenization treatment is performed on the Al alloy sheet material that has undergone the CC process. This heat treatment is performed at a temperature higher than the recrystallization temperature in order to reduce the processing strain applied to the Al alloy sheet during the CC process. The heat treatment conditions are 500 to 560 ° C. and 4 to 10 hours. Note that the homogenization process may be omitted depending on the processing conditions.

  A solution treatment is performed on the Al alloy sheet material that has undergone the heat treatment step. The solution treatment conditions are 500 to 550 ° C. for 1 hour or longer. Then, quench with warm water. As shown in FIG. 4, the heat treatment step and the solution treatment step can be performed continuously without lowering the heating temperature.

  The Al alloy sheet material that has undergone the solution treatment is subjected to press working as plastic working. First, as shown in FIG. 5, a blank of the vehicle body part 1 is punched out from an Al alloy sheet. Specifically, blanking is performed so that the longitudinal direction of the body part 1 is along the rolling direction of the Al alloy sheet. Here, the bending lines at the upper and lower edge portions of the vehicle body part 1 extend so as to substantially follow the rolling direction of the plate material. Generally, when a blank is bent in a direction along the rolling direction of the plate material, cracks and wrinkles are less likely to occur at the bent portion. And the blank obtained in this way is applied to a press machine, and press work is performed.

  Artificial aging treatment is applied to the Al alloy sheet material that has undergone this plastic working step. The processing conditions are about 170 to 200 ° C. and about 8 to 18 hours. By the artificial aging treatment, the alloy element that is forcibly dissolved in the Al alloy plate material by the solution treatment performed before press working and is in a supersaturated state returns to the original stable state. As a result, the alloy elements are precipitated in some places, and the precipitation makes it difficult for the dislocations to slip, and the physical properties, particularly the strength, of the plastically processed vehicle body part 1 are improved.

  As described above, by dividing the functions of rapid solidification and addition of the rolling load into the first roll 2 and the second roll 3, respectively, the cast structure is refined by the first roll 2 made of a material having high thermal conductivity, Due to the high rolling load of the second roll 3 formed of a material stronger than the first roll 2, it is possible to introduce processing strain inside the material, and further refinement of the recrystallized structure by heating above the recrystallization temperature. It becomes possible. In addition, an increase in the cooling rate can improve productivity, and an increase in the rolling load during casting can reduce the thickness of the member and improve the accuracy of the plate thickness. Can do.

A reference technique will be described with reference to FIG.
The difference from Example 1 is that the lower roll 1 is provided with two of a first lower roll 10 and a second lower roll 11. Other reference numerals are the same as those in the first embodiment.

This CC apparatus includes a first lower roll 10 of copper, the first roll 2 of copper disposed on a vertical plane above the first lower roll 10, positioned immediately downstream of the first lower roll 10 A second lower roll 11 made of steel and a second roll 3 made of steel disposed on the upper vertical surface of the second lower roll 11. A crucible 6, a nozzle 7, a rod 8, and a guide roller 9 are provided. The same as in the first embodiment.

  The first roll 2 and the second roll 3 are configured to be able to advance and retreat with respect to the first lower roll 10 and the second lower roll 11, and the first and second nips 4, 5 are caused by this advance / retreat operation. The rolling load for rolling the Al alloy sheet that passes through is controlled. The rolling load at the first nip 4 is set to 0.1 to 0.5 kN / mm, and the rolling load at the second nip 5 is set to 1 to 15 kN / mm.

  With the above configuration, the supplied molten metal is sandwiched between the first copper roll 2 and the first lower roll 10 that are disposed above and below, and as a result of significant rapid solidification, the cast structure is further improved. Miniaturization can be achieved. The first lower roll 10 and the second lower roll 11 can also be configured to be able to advance and retreat with respect to the first roll 2 and the second roll 3.

A second embodiment will be described with reference to FIG.
The difference from the first embodiment is the positional relationship between the first roll 2 and the second roll 3, and the other configurations are the same.

The rotation center of the second roll 3 made of steel is arranged on a substantially vertical plane passing through the rotation center of the lower roll 1 made of steel, and the first roll 2 made of copper is positioned below the second roll 3 in the vertical direction. doing.
With this configuration, the rolling load can be easily and stably applied from the second steel roll 3 to the Al alloy sheet.

FIG. 9 shows a third embodiment.
The difference from the first embodiment is that the first roll 2 and the second roll 3 are each provided with 2 rolls, 4 rolls in total.
With this configuration, the first rolls 2 and 2 can be rapidly cooled, and the solidification characteristics are improved. Furthermore, since the rolling load can be applied by the second rolls 3 and 3, the increase of the rolling load and the application form can be subdivided, and uniform and reliable processing strain can be introduced.

  Based on FIGS. 10-13, the heat processing conditions before the plastic working suitable for various Al type alloys are demonstrated. Since the 6000 series Al alloy (Al-Mg-Si series) has already been explained, the explanation here is omitted.

  Based on FIG. 10, the heat treatment conditions before plastic working in JIS standard 5000 series Al alloy (Al-Mg series) will be described.

  After the CC process, in order to homogenize the alloy components, a homogenization treatment is performed by heating to a temperature higher than the recrystallization temperature. This homogenization treatment is performed at 480 to 540 ° C. for 4 to 10 hours. Thereafter, rolling is performed hot or cold as necessary, and the entire Al alloy sheet is heated to 340 ° C. or higher, and after annealing, plastic processing such as pressing is performed. Since the Al alloy sheet is excellent in plastic workability and can produce a thin sheet of 3 mm or less, homogenization, rolling and tempering can be omitted.

  Based on FIG. 11, the heat treatment conditions before plastic working in a JIS standard 3000 series Al alloy (Al-Mn series) will be described.

  After the CC process, in order to homogenize the alloy components, a homogenization treatment is performed by heating to a temperature higher than the recrystallization temperature. This homogenization treatment is performed at 530 to 610 ° C. for 4 to 24 hours. Thereafter, rolling is performed hot or cold as necessary, and the entire Al alloy sheet is heated to 340 ° C. or higher, and after annealing, plastic processing such as pressing is performed. Since the Al alloy sheet is excellent in plastic workability and can produce a thin sheet of 3 mm or less, homogenization, rolling and tempering can be omitted.

  Based on FIG. 12, the heat treatment conditions before plastic working in JIS standard 1000 series Al (pure Al series) will be described.

  After the CC process, in order to homogenize the alloy components, a homogenization treatment is performed by heating to a temperature higher than the recrystallization temperature. This homogenization treatment is performed at 500 to 560 ° C. for 1 to 10 hours. Thereafter, rolling is performed hot or cold as necessary, and the entire Al plate is heated to 340 ° C. or higher, and after annealing, plastic processing such as pressing is performed. Since the Al alloy sheet is excellent in plastic workability and can produce a thin sheet of 3 mm or less, homogenization, rolling and tempering can be omitted.

  Based on FIG. 13, the heat treatment conditions before plastic working in a JIS standard AZ-based Mg alloy (Mg—Al—Zn-based) will be described.

  After the CC step, hot rolling is performed as necessary, and the entire Mg alloy sheet is heated to 100 to 200 ° C. or higher, and after annealing, plastic processing such as pressing is performed. Since this Mg alloy sheet is excellent in plastic workability and can produce a thin sheet of 3 mm or less, rolling and tempering can also be omitted.

  With the above configuration, the metal structure can be refined and processing strain can be introduced into the material, and the recrystallized structure can be further refined by heating at a temperature higher than the recrystallization temperature. In addition, the productivity can be improved by increasing the cooling rate, and the thickness of the member can be reduced and the accuracy of the plate thickness can be improved by increasing the rolling load during casting.

  In addition, those skilled in the art can implement the present invention by adding various modifications without departing from the spirit of the present invention, and the present invention includes such modifications.

It is a figure which shows the vehicle body component in the best embodiment of this invention, Comprising: (a) is a side view, (b) is a rear view. It is process drawing which shows the manufacturing method of the said vehicle body component. It is a figure which shows the continuous casting rolling apparatus which concerns on Example 1. FIG. It is a time chart which shows the solution treatment conditions in the said embodiment. It is explanatory drawing of the plastic working process in the said embodiment. It is a time chart which shows the artificial aging treatment conditions in the said embodiment. It is a figure which shows the continuous casting rolling apparatus which concerns on a reference technique . It is a figure which shows the continuous casting rolling apparatus which concerns on Example 2. FIG. It is a figure which shows the continuous casting rolling apparatus which concerns on Example 3. FIG. It is process drawing which shows the manufacturing method before plastic working in 5000 series Al alloy. It is process drawing which shows the manufacturing method before plastic working in 3000 series Al alloy. It is process drawing which shows the manufacturing method before plastic working in 1000 type | system | group Al. It is process drawing which shows the manufacturing method before plastic working in AZ type Mg alloy. It is a schematic process drawing explaining the difference between DC method and CC method. It is explanatory drawing of a twin roll horizontal type continuous casting rolling method.

M Al alloy 1 Lower roll 2 Upstream roll 3 Downstream roll 4 First nip 5 Second nip 50 Car body parts

Claims (3)

In a continuous casting and rolling apparatus in which a molten metal of light metal or light metal alloy is poured between a pair of upper and lower rollers, and the molten metal is extruded as a plate-like continuous cast rolling material in the rolling direction while applying a rolling load by the rollers,
The upper stream side roll arranged upstream of the rolling direction,
And the lower stream side roll arranged downstream of the this upstream roller,
A single lower roll disposed on the lower side of the molten metal and positioned opposite the downstream roll, and applying a reduction load to the molten metal together with the downstream roll,
The upstream roll is formed of a material having higher heat conductivity than the downstream roll, and the downstream roll and the lower roll are formed of a material having higher strength than the upstream roll. Continuous casting and rolling equipment. The continuous casting and rolling apparatus according to claim 1, wherein the rotation center of the downstream roll is located on a substantially vertical plane passing through the rotation center of the lower roll . In the method of manufacturing a metal member using the continuous casting and rolling apparatus according to claim 1,
A first step of continuously casting and rolling a melt of light metal or light metal alloy;
A second step of performing a heat treatment to heat the continuous cast rolled material to a recrystallization temperature or higher during or after the continuous cast rolling,
The second step is a step of performing solution treatment by performing quenching after heating the continuous cast rolled material to a recrystallization temperature or higher,
A third step of plastically processing the continuously cast rolled material after the solution treatment;
A fourth step of performing artificial aging treatment after the plastic working;
The manufacturing method of the metal member characterized by having.