CN1718826A - Modified steel and its production method - Google Patents

Abstract

A modified steel with better casting properties, high strength, toughness and mechanical performance and low cost contains C (2.5-3.0%), Si (0.8-1.2), Mn (0.7-1.5), S (0-0.03), P (0-0.03) and Fe (rest). It is prepared through proportioning raw materials, smelting modifying by use of modifier, casting and heat treating.

Description

Modified steel and production method thereof

Technical field

The present invention relates to a kind of modified steel product of field of metallurgy and production method thereof.

Background technology

Spheroidal graphite cast iron occurs from the 19th-century end and come, made plain cast iron great variation take place in industrial application.To 20 th century later, owing to updating of alterant, graphite becomes point-like (particle diameter is in micron) by sheet, so " spotted graphite cast iron " this notion occurred.Spotted graphite cast iron after rotten all increases than the spheroidal graphite cast iron various aspects of performance.But the refinement problem of carbide never has substantial progress, makes the performance of cast iron can not get basic improvement all the time, although for many years this has been carried out a large amount of research and unremitting effort, effect is still obvious inadequately.

Summary of the invention

The technical problem to be solved in the present invention is, to the cast iron processing of going bad, makes the abundant refinement of carbide in the interior tissue of the cast iron after rotten the processing, thereby makes it and a similar new steel grade---the modified steel that forms of some steel.

Technical solution of the present invention is that a kind of modified steel and production method thereof that can realize above-mentioned target is provided.This modified steel contains 2.5～3.0% carbon, 0.8～1.2% silicon, and 0.7～1.5% manganese ,≤0.03% sulphur reaches≤0.03% phosphorus, and surplus is an iron.

The technological process of production of described modified steel is as follows:

(1), batching: in the mentioned component scope, select the shove charge of proper composition batching according to the workpiece purposes;

(2), fusing: melt in the temperature more than 1450 ℃;

(3), the rotten processing: promptly adopt alterant processings of go bad when molten iron temperature reaches 1450 ℃, the every stove consumption of alterant is 1.4～1.8% of every stove total metal content, and molten method adds or directly adding with dashing, and stirring was left standstill 3～5 minutes more then;

(4), foundry goods or ingot casting: casting, pouring temperature 〉=1300 ℃;

(5), heat treating castings or ingot casting thermal treatment:

Heat treating castings:

1. annealing: 400 ℃ of heat tracings one hour, furnace cooling (requirement eliminates stress), or 950 ℃ of heating 3 hours, furnace cooling (machining requirement);

2. quench: 950 ℃ are incubated 5 hours, are cooled to 800 ℃ of shrends.

Ingot casting thermal treatment: homogenizing annealing → thermal distortion → cold deformation → annealing → precision work → quenching → tempering.

The new metallic material that obtains as stated above, it has following characteristics to be called modified steel (claiming the BZ steel again):

(1), composition is simple, do not add any other alloying element, adds a small amount of alterant when only handling on the turn.And not high to the cast iron specification of quality, general 14～No. 18 casting iron get final product, so the cost of material is low.

(2), used 305 alterants do not contain the magnesium of easy generation flame smog, production environment safety.After cast iron is rotten, but the long period maintenance in hot metal ladle of its modification effect is particularly conducive to carrying out smoothly of casting work.And old material can melt down, and the old material that melts down can continue to keep the modification effect of certain degree, and is very favourable to saving alterant.

(3) ingot casting after rotten must pass through high temperature annealing.Its objective is controlling through the carbide particle form, quantity and the degree of scatter that have gone bad in the ingot casting, make its tissue that obtains helping further press working or mechanical workout, so that carry out various forming process (comprise forging, calendering, stretching and car, pincers, satisfy, mill, mill etc.) on demand.

(4) finish shaping work, can carry out various forms of thermal treatments as steel alloy.Through the workpiece that Q-tempering is handled, can obtain hardness and the 4-10J/cm of HRC55-65 ²Toughness.

(5) can add a small amount of alloying element in order to satisfy some property (as improving wear and corrosion behavior etc.),, not only can improve acidproof ability, but also can improve its mechanical property and hardening capacity as in raw material, adding a small amount of Cr.

Modified steel after rotten the processing its carbide by greatly " fragmentation ".Anneal subsequently only needs 950 ℃, and insulation in 3 hours just can be dissolved substantially, and matrix has become perlite+ferrite, only remaining a small amount of undissolved being distributed on the matrix of carbide.Because having perlite+ferrite after the modified steel annealing is matrix, makes this material have good pressure machining characteristics.The quenching structure of modified steel is the tissue of some tiny remaining carbide of distributing on the martensitic matrix, and is similar with organizing of many steel.Its performance is according to the needs that use, by the content of its C, Si, Mn and the heat treatment mode decision adopted, its mechanical property is shown in table (1):

Table (1)

Tensile strength 6b-MPa	Bending strength 6bb-MPa	Amount of deflection mm	Hardness HRC	Impact toughness ak/J/cm 2
					800-1000	700-1000	4.2-5.3	55-65	4-10

The processing performance of modified steel is as follows:

1., temperature of fusion is not too high, only need above 1450 ℃.Rotten processing is used towards molten method and is carried out in casting ladle, because of not containing Mg, does not have flame and volume of smoke towards molten process.Environmental protection condition is better.

2., cast in＞carry out more than 1300 ℃, because of carbon content near the eutectic point good fluidity.

3., the carbide of ingot casting annealing back " fragmentation " more easily is dissolved in matrix, a large amount of ferrites that exist make the annealed ingot casting that fabulous processing characteristics be arranged, not only can carry out car, pincers, dig, mill, grind, and can carry out forge hot, mold pressing, hot pressing, during hot rolling deformability can reach＞40%.Help materials processing and become sheet material, band, section bar, bar.

4., the material after shaping, can carry out various types of thermal treatments.Quenching+tempering can make the HRC of material bring up to 55-65.Be chilled to 800 ℃ in soak for some time, workpiece can directly be quenched in the entry, can not cause cracking and distortion.

5., because the BZ steel does not add other alloying element, so resistance of oxidation is relatively poor,, adds a spot of Al and get final product as need raisings resistance of oxidation.As also having the requirement of other property, can add a small amount of other and contain gold element, as in order to improve acidproof ability, can add a small amount of Cr.Cr not only can improve acidproof ability but also can also improve mechanical property.Also promptly improved modification effect.

6., because the matrix of BZ steel and the basically identical of steel, so the weldability of itself and steel is fine, the weld seam zone of transition is metallurgical binding.

7., modified steel can change the structure property of regular pig and graphitic cast iron largely.Its intensity, hardness and toughness index have reached the level of some steel alloy, can replace steel alloy to a great extent.

8., modified steel is the good cast material of a kind of cost lower performance, is again a kind of inexpensive material of processed-type with high deformability.GPRS rotten processing and corresponding heat treatment technics, just can accomplish the end in view.

9., according to the situation of the particularly uncommon precious metal huge price increase of current various metals, save Ni, Cr, Mo, V, steel alloy common element such as Ti, W----, be very important work.One of advantage of modified steel is exactly might the instead of part steel alloy.Therefore widely popularize modified steel and be one to the relevant thing of society.The application prospect of modified steel is estimated: modified steel had both had the composition of iron, had the tissue and the performance of steel again; Both had good casting essence, can bear a large amount of rock deformation pressures again, can also obtain high intensity and toughness after quenching, the tempering.And this modified steel cost is low, and good mechanical property can replace multiple steel alloy, and being is worth the structural material of exploitation energetically, has a wide range of applications, and is as follows referring to table (2) institute its applicable scope of example:

Table (2)

Industrial sector	The applicable scope of modified steel
		Automobile and tractor	Transmission shaft, steering shaft, 4000 horsepower diesels, gasoline engine crank, camshaft, spiral bevel gear, I. C. engine oil pump gear, gas-turbine cylinder dividing plate, step down gear hub, tractor moping pulley, upper track wheel.
Universal machine	The bent axle of air conditioning machinery, pneumatic press, refrigerator, oxygenerator and pump, cylinder sleeve, the suction mud pump housing
		Lathe	The main shaft of grinding machine, milling machine, lathe, machine tool guideway, precision machine tool lathe bed, principal post, worktable
Metallurgical, mine	The tooth axle of hoisting machinery, ball mill tooth axle, abrading-ball, ore chute, liner plate, mine tram wheel, the large and small car roller of bridge crane
		Casted die mould	Plastics die set, powder metallurgy pressing mold, refractory materials pressing mold, ceramic tile pressing mold, ferrous and nonferrous metals punching die

At present modified steel begins to use in some enterprises, as make ball grinding machine lining board and abrading-ball, roll, lead feed, aspects such as pressing mold, punch die, mold produce as a trial.

Embodiment

Embodiment 1, and the composition of this routine modified steel and content value thereof are: 2.5% carbon, and 0.8% silicon, 0.7% manganese, 0.025% sulphur and 0.025% phosphorus, surplus is an iron.

The technological process of production is as follows:

(1), batching: press the shove charge of mentioned component batching, total amount 200kg, wherein carbon 5kg, silicon 1.6kg, manganese 1.4kg, sulphur 0.05kg, phosphorus 0.05kg, 18# pig iron 132kg, steel scrap 59.9kg;

(2), fusing: adopt the 200kg intermediate frequency furnace, be warming up to 1450 ℃ of temperature with molten iron is melting;

(3), the rotten processing: when molten iron temperature reaches more than 1450 ℃, get 3 kilograms of usefulness of 305 alterants and dash molten method adding, the processing of going bad.Add the back liquid modified steel that melts in the stove is stirred, left standstill after the stirring 3 minutes;

(4), foundry goods: implement the foundry goods casting, pouring temperature＞1300 ℃;

(5), casting thermal treatment:

1., annealing (eliminating stress): 400 ℃ of heat tracings one hour, furnace cooling;

2., quench: 950 ℃ are incubated 5 hours, are cooled to 800 ℃ of insulations shrend in 30 fens.

Embodiment 2, and the composition of this routine modified steel and content value thereof are: 3.0% carbon, and 0.8% silicon, 1.2% manganese, 0.025% sulphur and 0.025% phosphorus, surplus is an iron.

The technological process of production is as follows:

(1), batching: press the shove charge of mentioned component batching, batching total amount 10t, wherein carbon 300kg, silicon 80kg, manganese 120kg, sulphur 5kg, phosphorus 5kg, 18# pig iron 8t, steel scrap 1.49t;

(2), fusing: smelting furnace is 10 tons of intermediate frequency furnaces, under 1450 ℃ of temperature iron is melted;

(3), the rotten processing: when molten iron temperature reaches more than 1450 ℃, get 305 alterant 150kg and directly add the processing of going bad.Energising is stirred to leave standstill after 2 minutes and was prepared casting in 5 minutes;

(4), ingot casting: implement the ingot casting casting, 1300 ℃ of pouring temperatures;

(5), ingot casting thermal treatment: homogenizing annealing → thermal distortion → cold deformation → annealing → precision work → quenching → tempering.Former procedures of above ingot casting production are the same with casting mold production to be fit to roll the ingot mould that plate requires during just to ingot casting instead.400 ℃ of mould Wen Yingda whats.Be described in detail as follows:

1. homogenizing annealing: 950 ℃ of stoves after 3 hours are cold.

2. heating before the hot rolling: 950 ℃ of heating in 3 hours, it is rolling to come out of the stove fast.Having rolled this passage needs annealing again, can be again through 950 ℃ of insulations annealing in 30 minutes.

In addition, want several major issues of idea to be in the modified steel production process:

(1), alterant: it is the critical material that modified steel is produced, and is formed by multiple combination of materials.Should adopt commercially available 305 alterants of main component by rare earth ferrosilicon, ferrosilicon, silicocalcium and trace element preparation.

(2), modified steel through rotten the processing after, must could obtain best effect through corresponding thermal treatment.

(3), the maximum characteristics of modified steel are iron to be become have the microstructure and property and the low production cost thereof of steel.Therefore, the exploitation modified steel should take into full account these characteristics.

(4), the modified steel behind the quenching and tempering, not only have high rigidity but also toughness is fine.

(5), the present invention is at rolling mill part in addition, automobile is part in addition, the making aspect of multiple kinds of molds replaces some steel alloy, can bring into play better acting on.

In the industrialness production test of embodiment 1～2, raw material exclusion, no dirt, no greasy dirt, non-corroding and other pollution.

Claims (3)

1, a kind of modified steel contains 2.5～3.0% carbon, 0.8～1.2% silicon, and 0.7～1.5% manganese ,≤0.03% sulphur reaches≤0.03% phosphorus, and surplus is an iron.

2, a kind of production method that is exclusively used in the described modified steel of claim 1 is characterized in that, this method is the following technological process of production:

(1), batching: in the mentioned component scope, selects the proper composition shove charge of preparing burden according to the workpiece purposes,

(2), the fusing: melt in the temperature more than 1450 ℃,

(3), the rotten processing: promptly adopt alterant processings of go bad when molten iron temperature reaches 1450 ℃, the every stove consumption of alterant is 1.4～1.8% of every stove total metal content, and molten method adds or directly adding with dashing, and stirring was left standstill 3～5 minutes more then,

(4), foundry goods or ingot casting: casting, pouring temperature 〉=1300 ℃,

(5), heat treating castings or ingot casting thermal treatment:

Heat treating castings:

1. annealing: 400 ℃ of heat tracings one hour, furnace cooling (requirement eliminates stress), or 950 ℃ of heating 3 hours, furnace cooling (machining requirement),

2. quench: 950 ℃ are incubated 5 hours, are cooled to 800 ℃ of shrends,

Ingot casting thermal treatment: homogenizing annealing → thermal distortion → cold deformation → annealing → precision work → quenching → tempering.

3, the production method of modified steel according to claim 2 is characterized in that, described alterant is 305 alterants.