I think you should replace the ScatterLine chart with a scatter chart or a composite chart with scatter and line layers. If you only intend to use the lines as control limits, I suggest a regular scatter chart with a little bit of drawing magic in the FillSceneGraph event. Here's a sample that should give you a very similar output to the first chart image:

private void Form1_Load(object sender, EventArgs e)
{
    DataTable dt = new DataTable();
    dt.Columns.Add("ScatterX", typeof(int));
    dt.Columns.Add("ScatterY", typeof(int));

    dt.Rows.Add(new object[] { 0, 3 });
    dt.Rows.Add(new object[] { 1, 6 });
    dt.Rows.Add(new object[] { 2, 9 });
    dt.Rows.Add(new object[] { 3, 5 });
    dt.Rows.Add(new object[] { 4, 3 });
    dt.Rows.Add(new object[] { 5, 2 });

    ultraChart1.ChartType = ChartType.ScatterChart;
    ultraChart1.ScatterChart.ColumnX = 0;
    ultraChart1.ScatterChart.ColumnY = 1;
    ultraChart1.Axis.X.TickmarkStyle = AxisTickStyle.Smart;
    ultraChart1.Axis.Y.TickmarkStyle = AxisTickStyle.Smart;

    ultraChart1.Axis.Y.RangeMin = 0;
    ultraChart1.Axis.Y.RangeMax = 10;
    ultraChart1.Axis.Y.RangeType = AxisRangeType.Custom;

    ultraChart1.DataSource = dt;

    ultraChart1.FillSceneGraph += new Infragistics.UltraChart.Shared.Events.FillSceneGraphEventHandler(ultraChart1_FillSceneGraph);
}

void ultraChart1_FillSceneGraph(object sender, Infragistics.UltraChart.Shared.Events.FillSceneGraphEventArgs e)
{
    if (e.Grid.Count == 0)
        return;

    double min = e.ChartCore.GetChartLayer().GetData().GetDataMinColumn(1);
    double max = e.ChartCore.GetChartLayer().GetData().GetDataMaxColumn(1);

    IAdvanceAxis xAxis = (IAdvanceAxis)e.Grid["X"];
    IAdvanceAxis yAxis = (IAdvanceAxis)e.Grid["Y"];

    Line UCL = new Line();
    UCL.p1 = new Point((int)xAxis.MapMinimum, (int)yAxis.Map(max));
    UCL.p2 = new Point((int)xAxis.MapMaximum, (int)yAxis.Map(max));
    UCL.PE.Stroke = Color.Red;
    UCL.PE.StrokeWidth = 3;

    Line LCL = new Line();
    LCL.p1 = new Point((int)xAxis.MapMinimum, (int)yAxis.Map(min));
    LCL.p2 = new Point((int)xAxis.MapMaximum, (int)yAxis.Map(min));
    LCL.PE.Stroke = Color.Red;
    LCL.PE.StrokeWidth = 3;

    e.SceneGraph.Add(UCL);
    e.SceneGraph.Add(LCL);
}