CN110653340B

CN110653340B - Manufacturing method of external block steel casting of width fixing machine

Info

Publication number: CN110653340B
Application number: CN201810701202.7A
Authority: CN
Inventors: 熊杰; 廖永锋; 李伯林; 樊建成; 沈间
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2018-06-29
Filing date: 2018-06-29
Publication date: 2021-02-19
Anticipated expiration: 2038-06-29
Also published as: CN110653340A

Abstract

The invention discloses a method for manufacturing an outer block cast steel piece of a sizing machine, which comprises the following steps: 1) selecting a parting surface along the width direction of the outer block; 2) adding a machining allowance; 3) adding a sand core; 4) the lower part of the outer block of the width fixing machine is taken as the thickest position of the wall thickness, and the upper part is taken as the secondary thicknessing position of the wall thickness; setting pouring gate and pouring channel between the thickest position and the secondary thickest position; 5) the maximum thickness position and the secondary thickness position of the wall thickness are provided with a large riser and a small riser; 6) a chill is arranged at the thickest part of the wall thickness; 7) manufacturing a wood mold and a sand box; 8) a dead head, a pouring gate and a chill are arranged in the model; 9) the sand box is closed, the sand box is inclined according to the inclination of 1:8-1:10, and the large riser is positioned at the highest position of the casting; 10) pouring, namely pouring from a pouring gate at 1410-1430 ℃, stopping pouring when pouring to a large riser 1/2-2/3, pouring from the large riser instead, and performing point pouring for 2-3 times after the pouring is full; 11) opening the box; 12) normalizing; 13) and (6) tempering.

Description

Manufacturing method of external block steel casting of width fixing machine

Technical Field

The invention belongs to the technical field of machining and manufacturing, and particularly relates to a manufacturing method of an outer block cast steel piece of a hot rolling production line width fixing machine.

Background

The outer block blank of the hot rolling production line width fixing machine is shown in figure 1. The material of the casting was ZG230-450, which had profile dimensions of 2.0m (length) x 2.4m (width) x 3.5m (height) and weighed about 32 tons. The structure of the casting is complex, and the casting belongs to a large casting. The wall thickness of the casting is not uniformly distributed, the wall thickness of the lower part greatly exceeds the thick walls of the middle part and the upper part, and the middle part is also provided with a large cavity. Two round holes and grooves are arranged at the lower part of the casting and used for installing a width adjusting mechanism of the width fixing machine. The mechanical properties of the cast parts should meet the requirements of Table 1, and the ultrasonic flaw detection should meet the class II requirements specified in DIN EN12680-1 standard.

TABLE 1 mechanical Properties of the castings

	Rp(MPa)	Rm(MPa)	A5(％)	Z(％)
					Index (I)	≥225	≥450	≥19％	≥36％

The existing outer block casting process generally selects a parting surface along the height direction for molding and casting. When pouring, the lower part (the part with the thickest wall thickness) of the outer block is positioned at the bottom of the sand box, and a riser is difficult to be arranged for feeding the casting. Because the thickness of the lower part of the outer block is the thickest, if no riser feeding is available, the lower part of the outer block is easy to have casting defects such as core shrinkage cavity, shrinkage porosity and the like, and the quality and the mechanical property of a casting are influenced.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a method for manufacturing an outer block cast steel piece of a sizing machine.

The technical problem to be solved by the present invention can be implemented by the following technical means.

A manufacturing method of an outer block cast steel piece of a sizing machine comprises the following steps:

(1) selecting a parting surface along the width direction of the outer block;

(2) adding corresponding machining allowance on the outer block;

(3) adding sand cores at the positions of the round holes and the grooves;

(4) taking the lower part of the external block of the width fixing machine as the thickest position of the wall thickness and the upper part of the external block of the width fixing machine as the secondary thicknessing position of the wall thickness; according to the horizontal posture, the casting is in a casting pouring state, and a pouring gate and a pouring channel which are communicated with each other are arranged between the maximum wall thickness position and the secondary wall thickness position from top to bottom;

(5) a large riser is arranged at the thickest part of the wall thickness, and a small riser is arranged at the secondary thick part of the wall thickness;

(6) a chilling block is arranged at the thickest position of the wall thickness;

(7) manufacturing a wood mold and a sand box according to the process arrangement;

(8) mounting a riser, a pouring gate and a chill in the model;

(9) the mould assembling is carried out, wherein the sand box is inclined according to the inclination of 1:8-1:10, so that the large riser is positioned at the highest position of the casting;

(10) pouring, wherein the pouring temperature is controlled to be 1410-1430 ℃, pouring is firstly carried out from a pouring gate, when the pouring is carried out to about 1/2-2/3 of a large riser, pouring is carried out from the large riser, and point pouring is carried out for 2-3 times after the pouring is completed;

(11) opening the box after 72 hours, adopting vibration sand cleaning, mechanically cleaning the sand sticking and the chill on the surface of the outer block, and then cutting a large riser, a small riser and a pouring system;

(12) putting the cleaned casting into a furnace, and normalizing; the heating of the normalizing treatment is carried out in two steps:

1) the charging temperature is 250-300 ℃, the heating speed is not higher than 60 ℃ per hour, the temperature is heated to 650-700 ℃, and the temperature is preserved for 4-6 hours;

2) heating again to raise the temperature, wherein the temperature raising speed is not higher than 80 ℃ per hour, heating to 910 +/-10 ℃, keeping the temperature for 24-28 hours, discharging, and reducing the temperature to 350 ℃ of 300-;

(13) and (3) putting the casting subjected to normalizing into the furnace again, and tempering:

the charging temperature is 300-350 ℃, the heating speed is not higher than 60 ℃ per hour, the temperature is heated to 610 +/-10 ℃, the temperature is kept for 36-40 hours, the temperature is cooled to 450 ℃ along with the furnace at the cooling speed of not higher than 50 ℃ per hour, then the cooling speed is reduced to below 30 ℃/h, the casting is discharged after being continuously cooled to below 300 ℃, and the temperature is reduced to the normal temperature.

As a further improvement of the technical scheme, the large riser is a large open riser; the small riser is a small open riser.

As a further improvement of the technical scheme, the pouring gate comprises a vertical pouring gate and a horizontal pouring gate, the horizontal pouring gate is positioned at the bottom of the casting or close to the bottom, and the horizontal pouring gate is also connected with an inner pouring gate.

As a further improvement of the technical scheme, more than one cold iron is arranged at the thickest part of the wall thickness and is respectively arranged at the periphery of the round hole and the groove at the lower part of the outer block.

As one of the preferred embodiments of the invention, the steel casting is a plain carbon steel casting.

As another preferred embodiment of the present invention, in step (9), the flask is inclined at an inclination of 1: 10.

As still another preferred embodiment of the present invention, the heating of the normalizing treatment in the step (12) is carried out in two steps:

1) the charging temperature is 250-300 ℃, the heating speed is not higher than 60 ℃ per hour, and the temperature is heated to 650-700 ℃ and kept for 4 hours;

2) heating again to raise the temperature, wherein the temperature raising speed is not higher than 80 ℃ per hour, heating to 910 +/-10 ℃, keeping the temperature for 24 hours, discharging, and reducing the temperature to 350 ℃ by adopting forced air cooling of a blower;

tempering treatment is carried out in the step (13):

the charging temperature is 300-350 ℃, the heating rate is not higher than 60 ℃ per hour, the temperature is heated to 610 +/-10 ℃, the temperature is kept for 36 hours, the temperature is cooled to 450 ℃ along with the furnace at the cooling rate of not higher than 50 ℃ per hour, then the cooling rate is reduced to below 30 ℃/h, the casting is discharged after being continuously cooled to below 300 ℃, and the temperature is continuously reduced to the normal temperature through air cooling.

The mechanical properties of the external block cast steel piece of the fixed width machine manufactured by adopting the technical scheme are shown in table 2, the defect that the existing pouring method is easy to produce casting defects is overcome, and the external block cast steel piece has excellent casting quality and mechanical properties.

TABLE 2 measured values of mechanical properties of the castings

	Rp(MPa)	Rm(MPa)	A5(％)	Z(％)
					Technical index	≥225	≥450	≥19％	≥36％
Measured value	277	490	33％	65％

Drawings

FIG. 1 is a three-dimensional schematic diagram of a hot rolling production line width setter outer block blank;

FIG. 2 is a schematic view of a gating system of the width setter outer block;

FIG. 3 is a schematic diagram of a chill arrangement for an outer block casting of the sizing machine;

FIG. 4 is a graph of the normalizing treatment of the casting;

FIG. 5 is a graph of tempering of a casting;

in the figure: 1-pouring cup 2-sprue 3-cross gate 4-small open riser 5-large

open riser

6, 7, 8, 9, 10-chill

Detailed Description

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Referring to fig. 1 to 5, the invention discloses a method for manufacturing an outer block cast steel piece of a sizing machine. The method mainly comprises the processes of casting, heat treatment, machining and the like, and compared with the traditional method, the method selects a parting surface along the width direction of the outer block to perform die making and casting. The pouring system consists of a pouring cup 1, a sprue 2, a cross runner 3 and an ingate. The pouring mode is bottom pouring. A large riser (a large open riser 5) and

chills

6, 7, 8, 9 and 10 are arranged at the lower part (the thickest part of the wall thickness) of the outer block, and a small riser (a small open riser 4) is arranged at the upper part (the thicker part of the wall thickness) of the outer block. When molten steel is poured, the sand box is inclined according to the inclination of 1:10, and the lower part (the part with the thickest wall thickness) of the outer block is arranged at the highest position.

And the parting surface is selected along the width direction for molding and casting, so that the scouring of the molten steel on the sand mold and the sand core is reduced, and the molten steel can be favorably filled in the whole cavity smoothly. The pouring mode of bottom injection is adopted, so that stable filling of molten steel is facilitated, impact on a sand mold is small, exhaust is facilitated, and the molten steel enters a cross runner from a sprue and finally enters a cavity. When pouring, firstly pouring molten steel from a pouring gate, and when pouring to about 1/2-2/3 of the large open riser, pouring from the large open riser, and then performing point pouring for 2-3 times after the large open riser is fully poured.

The selection of the parting plane in the width direction is advantageous for providing large risers at the lower part of the outer block (the part with the thickest wall thickness) and small risers at the upper part of the outer block (the part with the thicker wall thickness) for feeding hot junction parts of the casting.

Chilling blocks are arranged on the circular hole at the lower part of the outer block and the periphery of the groove (the part with the thickest wall thickness) for artificial chilling, so that shrinkage cavities are prevented.

And (3) carrying out heat treatment of normalizing and tempering on the sand-cleaned casting to ensure the mechanical property of the casting.

Taking an example that an outer block of a width fixing machine of a certain hot rolling production line adopts ZG230-450 steel castings, the main manufacturing process comprises the following steps:

(1) the parting plane is selected in the width direction of the outer block.

(2) And adding corresponding machining allowance on the outer blocks.

(3) And adding sand cores at the positions of the round holes and the grooves.

(4) As shown in FIG. 2, a gate and a runner are provided.

(5) As shown in fig. 2, a large open riser 5 is arranged at the thickest part of the outer block, and a small open riser 4 is arranged at the other farthest end from the sprue.

(6) As shown in figure 3, 5

cold irons

6, 7, 8, 9 and 10 with different sizes are arranged at different positions of the circular hole at the lower part of the outer block and the periphery of the groove.

(7) And manufacturing a wood mold and a sand box according to the process arrangement.

(8) And a riser, a pouring gate and a chill are arranged in the model.

(9) And (4) assembling the sand box, wherein the sand box is inclined according to the inclination of 1:10, so that the large open riser is positioned at the highest position of the casting.

(10) And (3) pouring, wherein the pouring temperature is controlled to be 1410-1430 ℃, pouring is firstly carried out from a pouring gate, when the pouring is carried out to about 1/2-2/3 of the large open riser, pouring is carried out from the large open riser, and point pouring is carried out for 2-3 times after the pouring is full.

(11) And opening the box after 72 hours, adopting vibration sand cleaning, mechanically cleaning the sand sticking and the chill on the surface of the outer block, and then cutting the large open riser, the small open riser and the pouring system.

(12) The cleaned casting was charged into a furnace and normalized according to the heat treatment curve shown in FIG. 4. The heating of the normalizing treatment is carried out in two steps:

1) the charging temperature is 250-300 ℃, the heating speed is not higher than 60 ℃ per hour, the temperature is heated to 650-700 ℃, and the temperature is kept for 4-6 hours;

2) heating again to raise the temperature, wherein the temperature raising speed is not higher than 80 ℃ per hour, heating to 910 +/-10 ℃, keeping the temperature for 24-28 hours, discharging, and adopting a blower to cool to 350 ℃ by forced air cooling.

(13) The casting after the normalizing treatment was charged into the furnace again, and the tempering treatment was performed according to the heat treatment curve shown in fig. 5. The charging temperature is 300-350 ℃, the heating rate is not higher than 60 ℃ per hour, the temperature is heated to 610 +/-10 ℃, the temperature is kept for 36-40 hours, the temperature is cooled to 450 ℃ along with the furnace at the cooling rate of not higher than 50 ℃ per hour, then the cooling rate is reduced to below 30 ℃/h, the casting is discharged after being continuously cooled to below 300 ℃, and the temperature is continuously reduced to the normal temperature through air cooling.

The ZG230-450 steel casting manufactured by the method has the mechanical properties meeting the requirements of Table 1, and the ultrasonic flaw detection result meets the II-level requirements specified by the DIN EN12680-1 standard, and can be applied to the outer block of the hot-rolled strip steel width fixing machine. The technology can be popularized to the manufacture of large steel castings with similar shapes.

Compared with the prior art, the manufacturing method of the outer block of the width fixing machine of the hot-rolled strip steel production line has the advantages that the outer block is a common carbon steel cast steel piece, and a parting surface is selected along the width direction; and large and small risers are arranged at the two parts with the thickest wall thickness of the outer block and are used for feeding castings. And (3) arranging a chilling block at the position with the thickest wall thickness of the outer block, and carrying out artificial chilling to prevent the occurrence of shrinkage cavity. The outer block casting adopts a bottom pouring process. When pouring, firstly pouring molten steel from a pouring gate, and when pouring to about 1/2-2/3 of the large open riser, pouring from the large open riser, and then performing point pouring for 2-3 times after the large open riser is fully poured. And after casting, adopting a normalizing and tempering heat treatment process. Thereby providing casting quality and mechanical properties.

Claims

1. A manufacturing method of a steel casting of an outer block of a sizing mill, wherein the outer block adopts ZG230-450 steel casting, is characterized by comprising the following steps:

(1) selecting a parting surface along the width direction of the outer block;

(2) adding corresponding machining allowance on the outer block;

(3) adding sand cores at the positions of the round holes and the grooves;

(8) mounting a riser, a pouring gate and a chill in the model;

(10) pouring, wherein the pouring temperature is controlled to be 1410-1430 ℃, pouring is firstly carried out from a pouring gate, when pouring is carried out to a large riser 1/2-2/3, pouring is carried out from the large riser, and point pouring is carried out for 2-3 times after pouring is completed;

2. The method of manufacturing a sizing mill billet according to claim 1, wherein the large riser is a large open riser; the small riser is a small open riser.

3. The method for manufacturing the sizing machine exterior block steel casting according to claim 1, wherein the pouring channel comprises a vertical pouring channel and a horizontal pouring channel, the horizontal pouring channel is positioned at the bottom or near the bottom of the casting, and the horizontal pouring channel is also connected with an inner pouring channel.

4. The method for manufacturing the sizing machine outer block cast steel piece according to claim 1, wherein the position with the thickest wall thickness is provided with more than one cold iron, and the more than one cold iron are respectively arranged on the periphery of the circular hole and the groove at the lower part of the outer block.

5. The method for manufacturing a sizing mill slab steel according to claim 1, wherein in the step (9), the sand box is inclined at an inclination of 1: 10.

6. The method for manufacturing a sizing mill billet according to claim 1, characterized in that the heating of the normalizing treatment in step (12) is carried out in two steps:

tempering treatment is carried out in the step (13):