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The reasons and solutions of steel casting subcutaneous blowhole PowerPoint PPT Presentation


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Many steel casting parts may have subcutaneous blowholes. There may be some different reasons,during casting process, any one step is not correct, it will lead to blowholes. Now let’s analyze thereasons and solutions from material,iron melting,sand mixing etc.

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The reasons and solutions of steel casting subcutaneous blowhole

The

The reasons

reasons and

and solutions

solutions of

of steel

steel casting

casting subcutaneous

subcutaneous

blowhole

blowhole

Many steel casting parts may have subcutaneous blowholes. There may be some different reasons,

during casting process, any one step is not correct, it will lead to blowholes. Now let’s analyze the

reasons and solutions from material,iron melting,sand mixing etc.

1. raw material

1).material with Ti,Al ,high alloy steel and stainless steel should be forbidden.

2).Material with rusted, oxidation serious, greasy dirt, coal slime, a lot of antiquated sand, must be

cleaned.

3). Moist,material with water,must be dried.

4).thickness of sheet iron(tube) is less than 3mm,must be forbidden.

5).The length of material is 300-400mm.

2.Iron melting

1).when put raw material into furnace,must be compacted,try the best to reduce interspace,in order

to reduce liquid iron to inhale and oxidize.

2).In the process of melting iron of each furnace,must clean cinder thoroughly 2-3 times,and liquid

iron must be covered slag accretion and thermal insulation material,to avoid liquid iron expose in the

air for a long time.

3).liquid iron can’t wait more than 10-15 minutes in high temperature,or liquid iron will be Stagnant

water.

4). Tapping temperature can’t be less than 1540±10℃,after tapping iron,remove slag in time,and

cover dregs remover,to prevent liquid iron cooling and oxidation.

5). Carburant doesn’t meet the standard is forbidden.


The reasons and solutions of steel casting subcutaneous blowhole

3. Nucleating agent

1). Nucleating agent should be baking 300-400℃ before using, removal of its adsorption of water

and crystal water.

2).Particle size of nucleating agent is 5-10mm.

3).Al content of nucleating agent is less than 1%

4,Pouring

1).Big,small ladle must be dry, wet ladle is forbidden,can’t use liquid iron to burn ladle to instead of

baking.

2).improve pouring temperature, pouring quickly with high temperature. Pouring principle:

slow-quick-slow. Practices show that improve pouring temperature 30-50℃,can reduce occurrence

rate of gas hole. While pouring, liquid iron must be full of straight, sprue, can’t be cut off, in order to

build static pressure of liquid iron, to prevent air invading.

3).Small ladle can‘t be used when temperature is less than 1350℃,should be melt down.

4).Enhance pushing off slag, cover slag, and scale handling, prevent it into cavity.

5.Sand mixing

1). Moisture of moulding sand must be strictly controlled less than 3.5%

2). Air permeability of moulding sand must be controlled 130-180, green compression strength is

120-140Kpa, compaction rate is 35-38%,hardness of moulding sand surface >90.

3).choose high quality bentonite and pulverized coal

4).Mixing new sand according to the rules

5).must recycle the balance sand mouding after sand mixing everyday,and clean sand mixer.

6.Tooling and moulding

1).Die joint of tooling need to make vent groove or vent channel and dark gas chamber

2).add dark gas chamber to reduce gas pressure.

3). Scatter cryolite powder on cross gate or sand core.

7.Core making

1). containing water of silica sand is less than 0.2%,silt content is less than 0.3%

2).technic of core making:before sand mixing, silica sand need to be heated to 25-35℃,firstly add

part 1 into sand, mixing 1 to 2 minutes,then add part 2 ,mixing 1 to 2 minutes.

3).Since ployisocyanate is sensitive to water, core can’t be stored more than 24 hours.

4).High concentration and residual quantity of triethylamine is easy to cause ubcutaneous blowhole

For more info , welcome to visit our website at : www.casting-forgings.com


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