Method of hot rolling of thick sheets from copper alloys

FIELD: metallurgy.

SUBSTANCE: method includes heating of a flat stock and its multi-pass pressing in working rollers. Exclusion of formation of internal defects in rolled metal is achieved by the fact that heating of the stock is carried out to temperature of 750-850°C, and pressing in each of passes is regulated by mathematical dependence.

EFFECT: increased quality of thick-sheet rolled metal from hard-to-deform copper alloys with lower process plasticity.

1 tbl, 6 ex

 

The method of hot-rolled thick plates of copper alloy

The invention relates to rolling production and can be used to obtain thick sheets of hard copper alloys with low technological plasticity.

There is a method of rolling sheets of copper alloy comprising heating the ingot to a temperature of 820°C and subsequent multi-pass hot and cold rolling with a regulated reductions [1].

The disadvantage of this method is that during rolling of copper alloys with low technological plasticity in the leaves form the internal defects such as cracks and breaks that affects the quality of the products and reduces the yield.

The closest analogue of the present invention is a method of rolling thick sheets of copper alloys, including heat flat blanks, multipass hot rolling in the temperature range 780-450°C and subsequent cold rolling [2].

The disadvantages of this method are that when the rolling of thick sheets of copper alloys with low technological plasticity deformation produced by the working rolls is attenuated by the thickness of the blank and does not extend across the whole width. The uneven deformation in thickness leads to the formation in the Central layers of leaves cracks razryvov. This reduces the quality and yield of plates.

The technical problem solved by the present invention is to improve the quality and yield of thick sheets of copper alloys with low technological plasticity.

To solve the technical problem in the known method of hot-rolled thick plates of copper alloys, including heat flat blanks and multi-pass compression in the working rolls, according to the invention, the heating of the workpiece lead to a temperature of 750-850°C, and the compression in each of the passages set value:

εa0+ea1h0De0,19f,

where h0the thickness of the workpiece before the passage;

D - diameter work rolls;

f is the coefficient of external friction;

a0=-0,9038+0,0272·µ3;

a1=0,2490+0,1848·µ3;

µ is the Poisson's ratio of the copper alloy at a temperature of deformation.

The invention consists in the following. In the process of hot rolling of flat blanks of copper alloy in plates under compression in each of the passages has an uneven strain on its thickness: deformation of m is ximala the contact surfaces of the workpiece, interacting with the working rolls, unevenly and quickly fades out to the middle of it, that does not preclude the formation of internal defects such as cracks and breaks.

In the course of the experiments was determined empirical dependence of the minimum allowable relative compression 8 on temperature and other parameters of rolling and properties of copper alloy, wherein during compression between the work rolls deformation guaranteed penetrates the entire thickness of the workpiece. Therefore, when the condition is met:

εa0+ea1h0De0,19f

the rolling of thick sheets of copper alloys occurs without the formation of internal cracks and breaks. Specified experimentally definite correlation was obtained for the conditions of rolling copper alloys thickness 10-90 mm the Exception of the formation of internal defects, in turn, increased the yield of plates.

It is found experimentally that when the heating temperature above 850°C due to the oxidation of the grain boundaries of the copper alloy in the rolling process, the formation of trading the peal, which reduces the yield. Lowering the temperature below 750°C degrades the ductility of copper alloys and uniformity of deformation in thickness of the workpiece. It stimulates the formation of defects and leads to reduced yield.

Also experimentally found that when the relative compression for passage

ε<a0+ea1h0De0,19f

deformation from the side of the work rolls does not cover the entire thickness of the flat blanks that leads to it internal defects and reduced yield.

Examples of implementation of the method

Cast flat workpiece thickness h0=100 mm of copper alloy grades BRB with chemical composition, wt.%:

FeSiNiAlPbBeCu+impurity
0,150,150,50,150,005 2,1rest

heated in a gas furnace to a temperature of T=800°C, serves to reverse I Duo with a diameter steel work rolls D=700 mm For the reference data to determine the coefficient of external friction during hot rolling f=0.3 and Poisson's ratio of this copper alloy at a temperature deformation µ=0,5.

Calculate the parameters and0and a1:

and0=-0,9038+0,0272·µ3=-0,9038+0,0272·0,53=-0,9004;

and1=0,2490+0,1848·µ3=0,2490+0,1848·0,53=0,2 721,

then calculate the minimum value of the relative compression in the first pass, at which plastic deformation from the work rolls penetrates the entire thickness of the workpiece:

ε=a0+ea1h0De0,19f=-0,9004e0,272165700e0,190,3=0,0684.

With the help of push mechanisms set mijalkovic gap and produce compression of a flat workpiece in the first aisle is of thickness h 0=100 mm and thickness h1=90 mm with a relative compression εfequal to:

εf=h0-h1h0=100mm-90mm100mm=0,10>ε=0,0684.

Since the actual value of the relative compression εfexceeds the minimum value of ε, the plastic deformation from the upper and lower work rolls more evenly and penetrates the entire thickness of the flat blanks, which prevents the formation of cracks and breaks in its inner layers.

Similarly calculate εffor the second and subsequent passes, setting the actual compression in each of them in accordance with the ratio εf≥ε. Rolling carry out to obtain sheets with thickness of 20 mm.

Due to the fact that in each of the passages of the plastic deformation from the rolls penetrates the entire thickness of the rolled blank is uniform, no formation of cracks and breaks in its inner layers, the yield of thick sheets of hard copper alloys increases and reaches the value Q=99,7%.

Options real is the organization of the proposed method and the indicators of efficiency listed in the table.

From the data given in the table, it follows that if implementation of the proposed method (options No. 2-4) are excluded education in a thick sheet of copper alloy internal cracks and breaks, resulting in increasing the yield of metal.

Table
Modes hot-rolled copper alloy brand BRB and the yield
№ p/pT, °CεInternal defectsQ %
1.740ε<a0+ea1h0De0,19fcracks, breaks78,8
2.750ε=a0+ea1h0 De0,19fno99,6
3.800ε>a0+ea1h0De0,19fno99,7
4.850ε>a0+ea1h0De0,19fno99,6
5.860ε<a0+ea1h0D e0,19fcracks, breaks78,7
6.[2]700not regulatedcracks, breaks75,3

With exorbitant values of the declared options (options # 1 and # 5), and the implementation of the known method (option # 6) is the formation of cracks and breaks in the plate rolled from hard copper alloys with low technological plasticity, which, in turn, leads to reduced yield.

Technical appraisal and economic benefits of the proposed method consist in the fact that heating the billet to a temperature of 750-850°C and subsequent compression in each of the aisles not less than the value specified on experimentally determined value, provides the penetration of plastic deformation and its uniform distribution throughout the thickness of the sheet. Because of this, as the test showed, is improving the quality and yield of thick sheets of copper alloys with low technological plasticity.

As the base object is accepted, the closest analogue. The use of the proposed JV is soba increase profitability sheets of a thickness of 8-50 mm made of hard copper alloys by 25-35%.

Sources of information

1. Berman, S. Copper-Bellevue alloys, their properties, applications and processing. M.: metallurgy, 1966, s, 254.

2. The patent of Russian Federation №2223157, IPC B21B 3/00, 2004

The method of hot-rolled thick plates of copper alloys, including heat flat blanks of copper alloy and multi-pass compression in the working rolls, characterized in that the heating of the workpiece lead to a temperature of 750-850°C, and the compression in each of the passages set by the ratio:

where h0the thickness of the workpiece before passage, mm.
D - diameter work rolls, mm;
f is the coefficient of external friction;
and0=-0,9038+0,0272·µ3;
a1=0,2490+0,1848·µ3;
µ is the Poisson's ratio of the copper alloy billet at a temperature of deformation.



 

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